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{L02} Inductors and Capacitors.

A-001-001-001    1-1-1
What is the meaning of the term "time constant" in an RL circuit ?
The time required for the current in the circuit to build up to 63.2% of the maximum value
The time required for the current in the circuit to build up to 36.8% of the maximum value
The time required for the voltage in the circuit to build up to 63.2% of the maximum value
The time required for the voltage in the circuit to build up to 36.8% of the maximum value
> Inductance is a property of circuits that oppose changes in current.  The time constant is the time current WOULD need to reach final value IF the initial rate of change COULD be maintained.  The time constant in seconds equals L in henrys divided by R in ohms:  the lower the resistance, the greater the rate of change resulting in greater opposition.  The current after 1, 2 and 5 time constants is respectively 63%, 87% and 100% of the final value.  With capacitors, the ratios are the same but they relate to voltage;  the time constant then becomes R times C.
A-001-001-002    1-1-2
What is the term for the time required for the capacitor in an RC circuit to be charged to 63.2% of the supply voltage?
One time constant
An exponential rate of one
A time factor of one
One exponential period
> Capacitance is a property of circuits that oppose changes in voltage.  Under charging conditions, the time constant is the time voltage WOULD need to reach the final value IF the initial rate of change COULD be maintained.  The time constant in seconds equals R in ohms times C in farads:  the higher the resistance, the longer the time.  The voltage after 1, 2 and 5 times constants is respectively 63%, 87% and 100% of the final value.  With inductors, the ratios are the same but they relate to current;  the time constant then becomes L divided by R.
A-001-001-003    1-1-3
What is the term for the time required for the current in an RL circuit to build up to 63.2% of the maximum value?
One time constant
An exponential period of one
A time factor of one
One exponential rate
> Inductance is a property of circuits that oppose changes in current.  The time constant is the time current WOULD need to reach final value IF the initial rate of change COULD be maintained.  The time constant in seconds equals L in henrys divided by R in ohms:  the lower the resistance, the greater the rate of change resulting in greater opposition.  The current after 1, 2 and 5 time constants is respectively 63%, 87% and 100% of the final value.  With capacitors, the ratios are the same but they relate to voltage;  the time constant then becomes R times C.
A-001-001-004    1-1-4
What is the term for the time it takes for a charged capacitor in an RC circuit to discharge to 36.8% of its initial value of stored charge?
One time constant
A discharge factor of one
An exponential discharge of one
One discharge period
> Key word:  DISCHARGE. The time constant is the time voltage WOULD need to reach the final value IF the initial rate of change COULD be maintained.  The time constant in seconds equals R in ohms times C in farads:  the higher the resistance, the longer the time.  The voltage after 1, 2 and 5 times constants is respectively 63%, 87% and 100% of the final value.  Heading towards ZERO, we are left with 37% (100 minus 63) and 13% (100 minus 87) respectively after 1 and 2 time constants.
A-001-001-005    1-1-5
What is meant by "back EMF"?
A voltage that opposes the applied EMF
A current that opposes the applied EMF
An opposing EMF equal to R times C percent of the applied EMF
A current equal to the applied EMF
> 'Back EMF' or 'counter electromotive force' is the voltage induced by changing current in an inductor.  It is the force opposing changes in current through inductors.
A-001-001-006    1-1-6
After two time constants, the capacitor in an RC circuit is charged to what percentage of the supply voltage?
86.5%
63.2%
95%
36.8%
> Capacitance is a property of circuits that oppose changes in voltage.  Under charging conditions, the time constant is the time voltage WOULD need to reach the final value IF the initial rate of change COULD be maintained.  The time constant in seconds equals R in ohms times C in farads:  the higher the resistance, the longer the time.  The voltage after 1, 2 and 5 times constants is respectively 63%, 87% and 100% of the final value.  With inductors, the ratios are the same but they relate to current;  the time constant then becomes L divided by R.
A-001-001-007    1-1-7
After two time constants, the capacitor in an RC circuit is discharged to what percentage of the starting voltage?
13.5%
36.8%
86.5%
63.2%
> Key word:  DISCHARGE. The time constant is the time voltage WOULD need to reach the final value IF the initial rate of change COULD be maintained.  The time constant in seconds equals R in ohms times C in farads:  the higher the resistance, the longer the time.  The voltage after 1, 2 and 5 times constants is respectively 63%, 87% and 100% of the final value.  Heading towards ZERO, we are left with 37% (100 minus 63) and 13% (100 minus 87) respectively after 1 and 2 time constants.
A-001-001-008    1-1-8
What is the time constant of a circuit having a 100 microfarad capacitor in series with a 470 kilohm resistor?
47 seconds
4700 seconds
470 seconds
0.47 seconds
> The time constant in seconds equals R in ohms times C in farads:  the higher the resistance, the longer the time.  In multiplying microfarads and megohms, the prefixes cancel one another.  100 microfarads times 0.470 megohm = 100 times 0.47 = 47 seconds.
A-001-001-009    1-1-9
What is the time constant of a circuit having a 470 microfarad capacitor in series with a 470 kilohm resistor?
221 seconds
221 000 seconds
47 000 seconds
470 seconds
> The time constant in seconds equals R in ohms times C in farads:  the higher the resistance, the longer the time.  In multiplying microfarads and megohms, the prefixes cancel one another.  470 microfarads times 0.470 megohm = 470 times 0.47 = 221 seconds.
A-001-001-010    1-1-10
What is the time constant of a circuit having a 220 microfarad capacitor in series with a 470 kilohm resistor?
103 seconds
470 000 seconds
470 seconds
220 seconds
> The time constant in seconds equals R in ohms times C in farads:  the higher the resistance, the longer the time.  In multiplying microfarads and megohms, the prefixes cancel one another.  220 microfarads times 0.470 megohm = 220 times 0.47 = 103 seconds.
A-001-002-001    1-2-1
What is the result of skin effect?
As frequency increases, RF current flows in a thinner layer of the conductor, closer to the surface
As frequency decreases, RF current flows in a thinner layer of the conductor, closer to the surface
Thermal effects on the surface of the conductor increase impedance
Thermal effects on the surface of the conductor decrease impedance
> Skin Effect is the tendency of AC to flow in an increasingly thinner layer at the surface of a conductor as frequency increases.
A-001-002-002    1-2-2
What effect causes most of an RF current to flow along the surface of a conductor?
Skin effect
Piezoelectric effect
Resonance effect
Layer effect
> Skin Effect is the tendency of AC to flow in an increasingly thinner layer at the surface of a conductor as frequency increases.
A-001-002-003    1-2-3
Where does almost all RF current flow in a conductor?
Along the surface of the conductor
In a magnetic field in the centre of the conductor
In a magnetic field around the conductor
In the centre of the conductor
> Skin Effect is the tendency of AC to flow in an increasingly thinner layer at the surface of a conductor as frequency increases.
A-001-002-004    1-2-4
Why does most of an RF current flow within a very thin layer under the conductor's surface?
Because of skin effect
Because the RF resistance of a conductor is much less than the DC resistance
Because a conductor has AC resistance due to self-inductance
Because of heating of the conductor's interior
> Skin Effect is the tendency of AC to flow in an increasingly thinner layer at the surface of a conductor as frequency increases.
A-001-002-005    1-2-5
Why is the resistance of a conductor different for RF currents than for direct currents?
Because of skin effect
Because of the Hertzberg effect
Because conductors are non-linear devices
Because the insulation conducts current at high frequencies
> Skin Effect is the tendency of AC to flow in an increasingly thinner layer at the surface of a conductor as frequency increases.
A-001-002-006    1-2-6
What unit measures the ability of a capacitor to store electrical charge?
Farad
Coulomb
Watt
Volt
> Capacitors store energy in an electrostatic field.  The capacitance in farads is one factor influencing how much energy can be stored in a capacitor.  The coulomb is a quantity of electrons ( 6 times 10 exponent 18 ).  One farad accepts a charge of one coulomb when subjected to one volt.  The watt is a rate of doing work (one joule per second).  One volt, a force, moves one coulomb with one joule of energy.
A-001-002-007    1-2-7
A wire has a current passing through it. Surrounding this wire there is:
an electromagnetic field
an electrostatic field
a cloud of electrons
a skin effect that diminishes with distance
> An electromagnetic field is the magnetic field created around a conductor carrying current.  A magnetic field is a space around a magnet or a conductor where a magnetic force is present.  A magnetic field is composed of magnetic lines of force.  An electrostatic field is the electric field present between objects with different static electrical charges.  An electric field is a space where an electrical charge exerts a force (attraction or repulsion) on other charges.
A-001-002-008    1-2-8
In what direction is the magnetic field oriented about a conductor in relation to the direction of electron flow?
In the direction determined by the left-hand rule
In all directions
In the same direction as the current
In the direct opposite to the current
> The 'Left-hand Rule':  position the left hand with your thumb pointing in the direction of electron flow; encircle the conductor with the remaining fingers, the fingers point in the direction of the magnetic lines of force.  [ Using conventional current flow, this would become the Right-hand rule. ]
A-001-002-009    1-2-9
What is the term for energy that is stored in an electromagnetic or electrostatic field?
Potential energy
Kinetic energy
Ampere-joules
Joule-coulombs
> Key word:  STORED.  Potential:  "capable of coming into being or action (Canadian Oxford)".  Kinetic:  "of or due to motion (Canadian Oxford)".
A-001-002-010    1-2-10
Between the charged plates of a capacitor there is:
an electrostatic field
a magnetic field
a cloud of electrons
an electric current
> Voltage across a capacitor creates an electrostatic field between the plates.  An electrostatic field is the electric field present between objects with different static electrical charges.  An electric field is a space where an electrical charge exerts a force (attraction or repulsion) on other charges.
A-001-002-011    1-2-11
Energy is stored within an inductor that is carrying a current. The amount of energy depends on this current, but it also depends on a property of the inductor. This property has the following unit:
henry
coulomb
farad
watt
> Inductors store energy in an electromagnetic field.  The inductance in henrys is one factor influencing how much energy can be stored in an inductor.  One henry produces one volt of counter EMF with current changing at a rate of one ampere per second.  The coulomb is a quantity of electrons ( 6 times 10 exponent 18 ).  One farad accepts a charge of one coulomb when subjected to one volt.  The watt is a rate of doing work (one joule per second).
A-001-003-001    1-3-1
What is the resonant frequency of a series RLC circuit if R is 47 ohms, L is 50 microhenrys and C is 40 picofarads?
3.56 MHz
1.78 MHz
7.96 MHz
79.6 MHz
> Resonant frequency equals 1 over ( 2 pi times the square root of L times C ).  Restating for frequency in megahertz becomes 1000 over ( 2 pi times the square root of microhenrys times picofarads ).  50 times 40 equals 2000 ;  The square root of 2000 is 44.7 ;  44.7 times 2 times 3.14 is 280.7 ;  1000 divided by 280.7 is 3.56 MHz.
A-001-003-002    1-3-2
What is the resonant frequency of a series RLC circuit, if R is 47 ohms, L is 40 microhenrys and C is 200 picofarads?
1.78 MHz
1.99 kHz
1.99 MHz
1.78 kHz
> Resonant frequency equals 1 over ( 2 pi times the square root of L times C ).  Restating for frequency in megahertz becomes 1000 over ( 2 pi times the square root of microhenrys times picofarads ).  40 times 200 equals 8000 ;  The square root of 8000 is 89.4 ;  89.4 times 2 times 3.14 is 561.4 ;  1000 divided by 561.4 is 1.78 MHz.
A-001-003-003    1-3-3
What is the resonant frequency of a series RLC circuit, if R is 47 ohms, L is 50 microhenrys and C is 10 picofarads?
7.12 MHz
7.12 kHz
3.18 MHz
3.18 kHz
> Resonant frequency equals 1 over ( 2 pi times the square root of L times C ).  Restating for frequency in megahertz becomes 1000 over ( 2 pi times the square root of microhenrys times picofarads ).  50 times 10 equals 500 ;  The square root of 500 is 22.4 ;  22.4 times 2 times 3.14 is 140.7 ;  1000 divided by 140.7 is 7.11 MHz.
A-001-003-004    1-3-4
What is the resonant frequency of a series RLC circuit, if R is 47 ohms, L is 25 microhenrys and C is 10 picofarads?
10.1 MHz
63.7 MHz
10.1 kHz
63.7 kHz
> Resonant frequency equals 1 over ( 2 pi times the square root of L times C ).  Restating for frequency in megahertz becomes 1000 over ( 2 pi times the square root of microhenrys times picofarads ).  25 times 10 equals 250 ;  The square root of 250 is 15.8 ;  15.8 times 2 times 3.14 is 99.2 ;  1000 divided by 99.2 is 10.08 MHz.
A-001-003-005    1-3-5
What is the resonant frequency of a series RLC circuit, if R is 47 ohms, L is 3 microhenrys and C is 40 picofarads?
14.5 MHz
13.1 MHz
13.1 kHz
14.5 kHz
> Resonant frequency equals 1 over ( 2 pi times the square root of L times C ).  Restating for frequency in megahertz becomes 1000 over ( 2 pi times the square root of microhenrys times picofarads ).  3 times 40 equals 120 ;  The square root of 120 is 11 ;  11 times 2 times 3.14 is 69.1 ;  1000 divided by 69.1 is 14.47 MHz.
A-001-003-006    1-3-6
What is the resonant frequency of a series RLC circuit, if R is 47 ohms, L is 4 microhenrys and C is 20 picofarads?
17.8 MHz
19.9 MHz
19.9 kHz
17.8 kHz
> Resonant frequency equals 1 over ( 2 pi times the square root of L times C ).  Restating for frequency in megahertz becomes 1000 over ( 2 pi times the square root of microhenrys times picofarads ).  4 times 20 equals 80 ;  The square root of 80 is 8.9 ;  8.9 times 2 times 3.14 is 55.9 ;  1000 divided by 55.9 is 17.89 MHz.
A-001-003-007    1-3-7
What is the resonant frequency of a series RLC circuit, if R is 47 ohms, L is 8 microhenrys and C is 7 picofarads?
21.3 MHz
28.4 MHz
2.84 MHz
2.13 MHz
> Resonant frequency equals 1 over ( 2 pi times the square root of L times C ).  Restating for frequency in megahertz becomes 1000 over ( 2 pi times the square root of microhenrys times picofarads ).  8 times 7 equals 56 ;  The square root of 56 is 7.5 ;  7.5 times 2 times 3.14 is 47.1 ;  1000 divided by 47.1 is 21.23 MHz.
A-001-003-008    1-3-8
What is the resonant frequency of a series RLC circuit, if R is 47 ohms, L is 3 microhenrys and C is 15 picofarads?
23.7 MHz
35.4 MHz
35.4 kHz
23.7 kHz
> Resonant frequency equals 1 over ( 2 pi times the square root of L times C ).  Restating for frequency in megahertz becomes 1000 over ( 2 pi times the square root of microhenrys times picofarads ).  3 times 15 equals 45 ;  The square root of 45 is 6.7 ;  6.7 times 2 times 3.14 is 42.1 ;  1000 divided by 42.1 is 23.75 MHz.
A-001-003-009    1-3-9
What is the resonant frequency of a series RLC circuit, if R is 47 ohms, L is 4 microhenrys and C is 8 picofarads?
28.1 MHz
49.7 MHz
49.7 kHz
28.1 kHz
> Resonant frequency equals 1 over ( 2 pi times the square root of L times C ).  Restating for frequency in megahertz becomes 1000 over ( 2 pi times the square root of microhenrys times picofarads ).  4 times 8 equals 32 ;  The square root of 32 is 5.7 ;  5.7 times 2 times 3.14 is 35.8 ;  1000 divided by 35.8 is 27.93 MHz.
A-001-003-010    1-3-10
What is the resonant frequency of a series RLC circuit, if R is 47 ohms, L is 1 microhenry and C is 9 picofarads?
53.1 MHz
5.31 MHz
17.7 MHz
1.77 MHz
> Resonant frequency equals 1 over ( 2 pi times the square root of L times C ).  Restating for frequency in megahertz becomes 1000 over ( 2 pi times the square root of microhenrys times picofarads ).  1 times 9 equals 9 ;  The square root of 9 is 3 ;  3 times 2 times 3.14 is 18.8 ;  1000 divided by 18.8 is 53.19 MHz.
A-001-003-011    1-3-11
What is the value of capacitance (C) in a series RLC circuit, if the circuit resonant frequency is 14.25 MHz and L is 2.84 microhenrys?
44 picofarads
2.2 microfarads
44 microfarads
2.2 picofarads
> Method A:  Reactances are equal at resonance.  XL = 2 times 3.14 times 14.25 times 2.84 = 254.2 ohms.  XC = 1 over ( 2 pi f C ).  Restating for f in megahertz and C in picofarads, XC = one million over 2 pi megahertz times picofarads.  Thus, C = one million over ( 2 pi f XC ) ;  2 times 3.14 times 14.25 times 254.2 = 22 748 ;   one million divided by 22 748 = 43.96 picofarads.  Method B:  at 14 MHz, C has to be in picofarads;  test the two answers in picofarads with "resonant frequency in megahertz equals 1000 over ( 2 pi times the square root of microhenrys times picofarads )".
A-001-004-001    1-4-1
What is the resonant frequency of a parallel RLC circuit if R is 4.7 kilohms, L is 1 microhenry and C is 10 picofarads?
50.3 MHz
15.9 kHz
50.3 kHz
15.9 MHz
> Resonant frequency equals 1 over ( 2 pi times the square root of L times C ).  Restating for frequency in megahertz becomes 1000 over ( 2 pi times the square root of microhenrys times picofarads ).  1 times 10 equals 10 ;  The square root of 9 is 3.2 ;  3.2 times 2 times 3.14 is 20.1 ;  1000 divided by 20.1 is 49.75 MHz.
A-001-004-002    1-4-2
What is the resonant frequency of a parallel RLC circuit if R is 4.7 kilohms, L is 2 microhenrys and C is 15 picofarads?
29.1 MHz
29.1 kHz
5.31 MHz
5.31 kHz
> Resonant frequency equals 1 over ( 2 pi times the square root of L times C ).  Restating for frequency in megahertz becomes 1000 over ( 2 pi times the square root of microhenrys times picofarads ).  2 times 15 equals 30 ;  The square root of 30 is 5.5 ;  5.5 times 2 times 3.14 is 34.5 ;  1000 divided by 34.5 is 28.99 MHz.
A-001-004-003    1-4-3
What is the resonant frequency of a parallel RLC circuit if R is 4.7 kilohms, L is 5 microhenrys and C is 9 picofarads?
23.7 MHz
23.7 kHz
3.54 MHz
3.54 kHz
> Resonant frequency equals 1 over ( 2 pi times the square root of L times C ).  Restating for frequency in megahertz becomes 1000 over ( 2 pi times the square root of microhenrys times picofarads ).  5 times 9 equals 45 ;  The square root of 45 is 6.7 ;  6.7 times 2 times 3.14 is 42.1 ;  1000 divided by 42.1 is 23.75 MHz.
A-001-004-004    1-4-4
What is the resonant frequency of a parallel RLC circuit if R is 4.7 kilohms, L is 2 microhenrys and C is 30 picofarads?
20.5 MHz
2.65 MHz
2.65 kHz
20.5 kHz
> Resonant frequency equals 1 over ( 2 pi times the square root of L times C ).  Restating for frequency in megahertz becomes 1000 over ( 2 pi times the square root of microhenrys times picofarads ).  2 times 30 equals 60 ;  The square root of 60 is 7.7 ;  7.7 times 2 times 3.14 is 48.4 ;  1000 divided by 48.4 is 20.66 MHz.
A-001-004-005    1-4-5
What is the resonant frequency of a parallel RLC circuit if R is 4.7 kilohms, L is 15 microhenrys and C is 5 picofarads?
18.4 MHz
2.12 kHz
2.12 MHz
18.4 kHz
> Resonant frequency equals 1 over ( 2 pi times the square root of L times C ).  Restating for frequency in megahertz becomes 1000 over ( 2 pi times the square root of microhenrys times picofarads ).  15 times 5 equals 75 ;  The square root of 75 is 8.7 ;  8.7 times 2 times 3.14 is 54.6 ;  1000 divided by 54.6 is 18.32 MHz.
A-001-004-006    1-4-6
What is the resonant frequency of a parallel RLC circuit if R is 4.7 kilohms, L is 3 microhenrys and C is 40 picofarads?
14.5 MHz
1.33 kHz
1.33 MHz
14.5 kHz
> Resonant frequency equals 1 over ( 2 pi times the square root of L times C ).  Restating for frequency in megahertz becomes 1000 over ( 2 pi times the square root of microhenrys times picofarads ).  3 times 40 equals 120 ;  The square root of 120 is 11 ;  11 times 2 times 3.14 is 69.1 ;  1000 divided by 69.1 is 14.47 MHz.
A-001-004-007    1-4-7
What is the resonant frequency of a parallel RLC circuit if R is 4.7 kilohms, L is 40 microhenrys and C is 6 picofarads?
10.3 MHz
6.63 MHz
6.63 kHz
10.3 kHz
> Resonant frequency equals 1 over ( 2 pi times the square root of L times C ).  Restating for frequency in megahertz becomes 1000 over ( 2 pi times the square root of microhenrys times picofarads ).  40 times 6 equals 240 ;  The square root of 240 is 15.5 ;  15.5 times 2 times 3.14 is 97.3 ;  1000 divided by 97.3 is 10.28 MHz.
A-001-004-008    1-4-8
What is the resonant frequency of a parallel RLC circuit if R is 4.7 kilohms, L is 10 microhenrys and C is 50 picofarads?
7.12 MHz
7.12 kHz
3.18 MHz
3.18 kHz
> Resonant frequency equals 1 over ( 2 pi times the square root of L times C ).  Restating for frequency in megahertz becomes 1000 over ( 2 pi times the square root of microhenrys times picofarads ).  10 times 50 equals 500 ;  The square root of 500 is 22.4 ;  22.4 times 2 times 3.14 is 140.7 ;  1000 divided by 140.7 is 7.11 MHz.
A-001-004-009    1-4-9
What is the resonant frequency of a parallel RLC circuit if R is 4.7 kilohms, L is 200 microhenrys and C is 10 picofarads?
3.56 MHz
3.56 kHz
7.96 MHz
7.96 kHz
> Resonant frequency equals 1 over ( 2 pi times the square root of L times C ).  Restating for frequency in megahertz becomes 1000 over ( 2 pi times the square root of microhenrys times picofarads ).  200 times 10 equals 2000 ;  The square root of 2000 is 44.7 ;  44.7 times 2 times 3.14 is 280.7 ;  1000 divided by 280.7 is 3.56 MHz.
A-001-004-010    1-4-10
What is the resonant frequency of a parallel RLC circuit if R is 4.7 kilohms, L is 90 microhenrys and C is 100 picofarads?
1.68 MHz
1.77 kHz
1.77 MHz
1.68 kHz
> Resonant frequency equals 1 over ( 2 pi times the square root of L times C ).  Restating for frequency in megahertz becomes 1000 over ( 2 pi times the square root of microhenrys times picofarads ).  90 times 100 equals 9000 ;  The square root of 9000 is 94.9 ;  94.9 times 2 times 3.14 is 596 ;  1000 divided by 596 is 1.68 MHz.
A-001-004-011    1-4-11
What is the value of inductance (L) in a parallel RLC circuit, if the resonant frequency is 14.25 MHz and C is 44 picofarads?
2.8 microhenrys
253.8 millihenrys
3.9 millihenrys
0.353 microhenry
> Method A:  Reactances are equal at resonance.  XC = 1 over ( 2 pi f C ).  Restating for f in megahertz and C in picofarads, XC = one million over (2 pi times megahertz times picofarads).  XC = one million divided by ( 2 times 3.14 times 14.25 times 44 ) = 254 ohms.  With XL = 2 pi f L, L is XL divided by 2 pi f:  254 divided by ( 2 times 3.14 times 14.25 ) = 2.8 microhenrys.  Method B:  at 14 MHz, L has to be in microhenrys;  test the two answers in microhenrys with "resonant frequency in megahertz equals 1000 over ( 2 pi times the square root of microhenrys times picofarads )".
A-001-005-001    1-5-1
What is the Q of a parallel RLC circuit, if it is resonant at 14.128 MHz, L is 2.7 microhenrys and R is 18 kilohms?
75.1
7.51
0.013
71.5
> Reactance = 2 pi f L = 2 times 3.14 times 14.128 times 2.7 = 240 ( the mega in megahertz cancels the micro in microhenrys).  Q = 18 000 divided by 240 = 75 .  In a PARALLEL circuit loaded by a resistor, Q = Resistance divided by Reactance:  the higher the parallel resistance, the lesser the effect on the response curve.  Parallel resistance lowers the Q of a parallel tuned circuit.  A parallel Damping Resistor is used to increase bandwidth.
A-001-005-002    1-5-2
What is the Q of a parallel RLC circuit, if it is resonant at 14.128 MHz, L is 4.7 microhenrys and R is 18 kilohms?
43.1
13.3
0.023
4.31
> Reactance = 2 pi f L = 2 times 3.14 times 14.128 times 4.7 = 417  ( the mega in megahertz cancels the micro in microhenrys).  Q = 18 000 divided by 417 = 43 .  In a PARALLEL circuit loaded by a resistor, Q = Resistance divided by Reactance:  the higher the parallel resistance, the lesser the effect on the response curve.  Parallel resistance lowers the Q of a parallel tuned circuit.  A parallel Damping Resistor is used to increase bandwidth.
A-001-005-003    1-5-3
What is the Q of a parallel RLC circuit, if it is resonant at 4.468 MHz, L is 47 microhenrys and R is 180 ohms?
0.136
7.35
0.00735
13.3
> Reactance = 2 pi f L = 2 times 3.14 times 4.468 times 47 = 1319  ( the mega in megahertz cancels the micro in microhenrys).  Q = 180 divided by 1319 = 0.136 .  In a PARALLEL circuit loaded by a resistor, Q = Resistance divided by Reactance:  the higher the parallel resistance, the lesser the effect on the response curve.  Parallel resistance lowers the Q of a parallel tuned circuit.  A parallel Damping Resistor is used to increase bandwidth.
A-001-005-004    1-5-4
What is the Q of a parallel RLC circuit, if it is resonant at 14.225 MHz, L is 3.5 microhenrys and R is 10 kilohms?
31.9
7.35
0.0319
71.5
> Reactance = 2 pi f L = 2 times 3.14 times 14.225 times 3.5 = 313 ( the mega in megahertz cancels the micro in microhenrys).  Q = 10 000 divided by 313 = 31.9 .  In a PARALLEL circuit loaded by a resistor, Q = Resistance divided by Reactance:  the higher the parallel resistance, the lesser the effect on the response curve.  Parallel resistance lowers the Q of a parallel tuned circuit.  A parallel Damping Resistor is used to increase bandwidth.
A-001-005-005    1-5-5
What is the Q of a parallel RLC circuit, if it is resonant at 7.125 MHz, L is 8.2 microhenrys and R is 1 kilohm?
2.73
36.8
0.368
0.273
> Reactance = 2 pi f L = 2 times 3.14 times 7.125 times 8.2 = 367 ( the mega in megahertz cancels the micro in microhenrys).  Q = 1000 divided by 367 = 2.7 .  In a PARALLEL circuit loaded by a resistor, Q = Resistance divided by Reactance:  the higher the parallel resistance, the lesser the effect on the response curve.  Parallel resistance lowers the Q of a parallel tuned circuit.  A parallel Damping Resistor is used to increase bandwidth.
A-001-005-006    1-5-6
What is the Q of a parallel RLC circuit, if it is resonant at 7.125 MHz, L is 10.1 microhenrys and R is 100 ohms?
0.221
22.1
0.00452
4.52
> Reactance = 2 pi f L = 2 times 3.14 times 7.125 times 10.1 = 452 ( the mega in megahertz cancels the micro in microhenrys).  Q = 100 divided by 452 = 0.22 .  In a PARALLEL circuit loaded by a resistor, Q = Resistance divided by Reactance:  the higher the parallel resistance, the lesser the effect on the response curve.  Parallel resistance lowers the Q of a parallel tuned circuit.  A parallel Damping Resistor is used to increase bandwidth.
A-001-005-007    1-5-7
What is the Q of a parallel RLC circuit, if it is resonant at 7.125 MHz, L is 12.6 microhenrys and R is 22 kilohms?
39
22.1
0.0256
25.6
> Reactance = 2 pi f L = 2 times 3.14 times 7.125 times 12.6 = 564 ( the mega in megahertz cancels the micro in microhenrys).  Q = 22 000 divided by 564 = 39 .  In a PARALLEL circuit loaded by a resistor, Q = Resistance divided by Reactance:  the higher the parallel resistance, the lesser the effect on the response curve.  Parallel resistance lowers the Q of a parallel tuned circuit.  A parallel Damping Resistor is used to increase bandwidth.
A-001-005-008    1-5-8
What is the Q of a parallel RLC circuit, if it is resonant at 3.625 MHz, L is 3 microhenrys and R is 2.2 kilohms?
32.2
25.6
31.1
0.031
> Reactance = 2 pi f L = 2 times 3.14 times 3.625 times 3 = 68 ( the mega in megahertz cancels the micro in microhenrys).  Q = 2200 divided by 68 = 32.3 .  In a PARALLEL circuit loaded by a resistor, Q = Resistance divided by Reactance:  the higher the parallel resistance, the lesser the effect on the response curve.  Parallel resistance lowers the Q of a parallel tuned circuit.  A parallel Damping Resistor is used to increase bandwidth.
A-001-005-009    1-5-9
What is the Q of a parallel RLC circuit, if it is resonant at 3.625 MHz, L is 42 microhenrys and R is 220 ohms?
0.23
2.3
4.35
0.00435
> Reactance = 2 pi f L = 2 times 3.14 times 3.625 times 42 = 956 ( the mega in megahertz cancels the micro in microhenrys).  Q = 220 divided by 956 = 0.23 .  In a PARALLEL circuit loaded by a resistor, Q = Resistance divided by Reactance:  the higher the parallel resistance, the lesser the effect on the response curve.  Parallel resistance lowers the Q of a parallel tuned circuit.  A parallel Damping Resistor is used to increase bandwidth.
A-001-005-010    1-5-10
What is the Q of a parallel RLC circuit, if it is resonant at 3.625 MHz, L is 43 microhenrys and R is 1.8 kilohms?
1.84
0.543
54.3
23
> Reactance = 2 pi f L = 2 times 3.14 times 3.625 times 43 = 979 ( the mega in megahertz cancels the micro in microhenrys).  Q = 1800 divided by 979 = 1.84 .  In a PARALLEL circuit loaded by a resistor, Q = Resistance divided by Reactance:  the higher the parallel resistance, the lesser the effect on the response curve.  Parallel resistance lowers the Q of a parallel tuned circuit.  A parallel Damping Resistor is used to increase bandwidth.
A-001-005-011    1-5-11
Why is a resistor often included in a parallel resonant circuit ?
To decrease the Q and increase the bandwidth
To increase the Q and decrease the skin effect
To decrease the Q and increase the resonant frequency
To increase the Q and decrease bandwidth
> A Damping Resistor can be placed across a parallel resonant circuit, or in series with a series resonant circuit, to lower the Q.  Reducing the Quality factor increases bandwidth.

' --  --  --  --

A-002-011-001    2-11-1
What is a crystal lattice filter?
A filter with narrow bandwidth and steep skirts made using quartz crystals
A filter with wide bandwidth and shallow skirts made using quartz crystals
An audio filter made with four quartz crystals that resonate at 1 kHz intervals
A power supply filter made with interlaced quartz crystals
> A filter with narrow bandwidth and steep skirts made with quartz crystals.  "Lattice: a structure of crossed laths with spaces between, used as a screen or fence."  The frequency separation between the crystals sets the bandwidth and the response shape.  Crystal lattice filter:  uses two matched pairs of series crystals and a higher-frequency matched pair of shunt crystals in a balanced configuration.  Half-lattice crystal filter: uses two crystals in an unbalanced configuration.  Such filters can be cascaded.  A 'Crystal Gate' uses a single crystal.
A-002-011-002    2-11-2
What factor determines the bandwidth and response shape of a crystal lattice filter?
The relative frequencies of the individual crystals
The centre frequency chosen for the filter
The gain of the RF stage following the filter
The amplitude of the signals passing through the filter
> A filter with narrow bandwidth and steep skirts made with quartz crystals.  "Lattice: a structure of crossed laths with spaces between, used as a screen or fence."  The frequency separation between the crystals sets the bandwidth and the response shape.  Crystal lattice filter:  uses two matched pairs of series crystals and a higher-frequency matched pair of shunt crystals in a balanced configuration.  Half-lattice crystal filter: uses two crystals in an unbalanced configuration.  Such filters can be cascaded.  A 'Crystal Gate' uses a single crystal.
A-002-011-003    2-11-3
For single-sideband phone emissions, what would be the bandwidth of a good crystal lattice filter?
2.4 kHz
15 kHz
500 Hz
6 kHz
> Speech frequencies on a communication-grade SSB voice channel range from 300 hertz to 3000 hertz and thus require a bandwidth of 2.7 kHz;  2.1 kHz is a good compromise between fidelity and selectivity.  15 kHz is the bandwidth of FM, 6 kHz is for AM, 500 Hz is a common filter width for CW.
A-002-011-005    2-11-5
A quartz crystal filter is superior to an LC filter for narrow bandpass applications because of the:
crystal's high Q
crystal's low Q
LC circuit's high Q
crystal's simplicity
> Piezoelectric crystals behave like tuned circuits with an extremely high "Q" ("Quality Factor", in excess of 25 000).  Their accuracy and stability are outstanding.
A-002-011-006    2-11-6
Piezoelectricity is generated by:
deforming certain crystals
touching crystals with magnets
adding impurities to a crystal
moving a magnet near a crystal
> The piezoelectric property of quartz is two-fold: apply mechanical stress to a crystal and it produces a small electrical field;  subject quartz to an electrical field and the crystal changes dimensions slightly.  Crystals are capable of resonance either at a fundamental frequency depending on their physical dimensions or at overtone frequencies near odd-integer multiples (3rd, 5th, 7th, etc.).  Piezoelectric crystals can serve as filters because of their extremely high "Q" (> 25 000) or as stable, noise-free and accurate frequency references.
A-002-011-007    2-11-7
Electrically, what does a crystal look like?
A very high Q tuned circuit
A very low Q tuned circuit
A variable capacitance
A variable tuned circuit
> Piezoelectric crystals behave like tuned circuits with an extremely high "Q" ("Quality Factor", in excess of 25 000).  Their accuracy and stability are outstanding.
A-002-011-010    2-11-10
Crystal oscillators, filters and microphones depend upon which principle?
Piezoelectric effect
Hertzberg effect
Ferro-resonance
Overtone effect
> The piezoelectric property of quartz (generating electricity under mechanical stress, bending when subjected to electric field) is used in crystal-based oscillators, radio-frequency crystal filters, such as the lattice filter, and crystal microphones.  The Active Filter is based on an active device, generally an operational amplifier, and a network of resistors and capacitors.
A-002-011-011    2-11-11
Crystals are not applicable to which of the following?
Active filters
Microphones
Lattice filters
Oscillators
> The piezoelectric property of quartz (generating electricity under mechanical stress, bending when subjected to electric field) is used in crystal-based oscillators, radio-frequency crystal filters, such as the lattice filter, and crystal microphones.  The Active Filter is based on an active device, generally an operational amplifier, and a network of resistors and capacitors.

' --  --  --  --

A-002-012-001    2-12-1
What are the three general groupings of filters?
High-pass, low-pass and band-pass
Hartley, Colpitts and Pierce
Audio, radio and capacitive
Inductive, capacitive and resistive
> There are 4 categories of filters:  high-pass, low-pass, band-pass and band-stop.  Hartley, Colpitts and Pierce are oscillator configurations.  "Capacitive" is not a range of frequencies like audio or radio.  Resistors do not discriminate frequency.
A-002-012-002    2-12-2
What are the distinguishing features of a Butterworth filter?
It has a maximally flat response over its pass-band
The product of its series and shunt-element impedances is a constant for all frequencies
It only requires conductors
It only requires capacitors
> The Butterworth class of filters exhibit "maximally flat response": smooth response, no passband ripple.  Their frequency response is as flat as mathematically possible in the passband, no bumps or variations (ripple) [first described by British engineer Stephen Butterworth].  The Chebyshev class of filters [in honour of Pafnuty Chebyshev, a Russian mathematician] have steeper cutoff slopes and more ripple than Butterworth filters.  Elliptic filters are sharper than the previous two.  Here is a mnemonic trick:  "The Butterworth's response is smooth as butter".
A-002-012-003    2-12-3
Which filter type is described as having ripple in the passband and a sharp cutoff?
A Chebyshev filter
An active LC filter
A passive op-amp filter
A Butterworth filter
> The Butterworth class of filters exhibit "maximally flat response": smooth response, no passband ripple.  Their frequency response is as flat as mathematically possible in the passband, no bumps or variations (ripple) [first described by British engineer Stephen Butterworth].  The Chebyshev class of filters [in honour of Pafnuty Chebyshev, a Russian mathematician] have steeper cutoff slopes and more ripple than Butterworth filters.  Elliptic filters are sharper than the previous two.  Here is a mnemonic trick:  "The Butterworth's response is smooth as butter".
A-002-012-004    2-12-4
What are the distinguishing features of a Chebyshev filter?
It allows ripple in the passband in return for steeper skirts
It requires only inductors
It requires only capacitors
It has a maximally flat response in the passband
> The Butterworth class of filters exhibit "maximally flat response": smooth response, no passband ripple.  Their frequency response is as flat as mathematically possible in the passband, no bumps or variations (ripple) [first described by British engineer Stephen Butterworth].  The Chebyshev class of filters [in honour of Pafnuty Chebyshev, a Russian mathematician] have steeper cutoff slopes and more ripple than Butterworth filters.  Elliptic filters are sharper than the previous two.  Here is a mnemonic trick:  "The Butterworth's response is smooth as butter".
A-002-012-005    2-12-5
Resonant cavities are used by amateurs as a:
narrow bandpass filter at VHF and higher frequencies
power line filter
low-pass filter below 30 MHz
high-pass filter above 30 MHz
> The quarter wavelength Resonant Cavity behaves like a very high "Q" filter.  Due to their physical size, they become practical only at VHF frequencies:  at 50 MHz (6 m), the length of the cavity is 1.5 m (one quarter wavelength).
A-002-012-006    2-12-6
On VHF and above, 1/4 wavelength coaxial cavities are used to give protection from high-level signals. For a frequency of approximately 50 MHz, the diameter of such a device would be about 10 cm (4 in). What would be its approximate length?
1.5 metres (5 ft)
0.6 metres (2 ft)
2.4 metres (8 ft)
3.7 metres (12 ft)
> The quarter wavelength Resonant Cavity behaves like a very high "Q" filter (around 3000).  Due to their physical size, they become practical only at VHF frequencies:  at 50 MHz (6 m), the length of the cavity is 1.5 m (one quarter wavelength).
A-002-012-007    2-12-7
A device which helps with receiver overload and spurious responses at VHF, UHF and above may be installed in the receiver front end. It is called a:
helical resonator
diplexer
directional coupler
duplexer
> The Helical Resonator, based on the concept of a resonant helically-wound section of transmission line within a shielded enclosure, achieves selectivity comparable to the quarter-wave resonant cavity but with a substantial size reduction.
A-002-012-008    2-12-8
Where you require bandwidth at VHF and higher frequencies about equal to a television channel, a good choice of filter is the:
none of the other answers
resonant cavity
Butterworth
Chebyshev
> The bandwidth of a fast-scan TV channel is 6 MHz;  that is much too wide for any of the filters listed.
A-002-012-009    2-12-9
What is the primary advantage of the Butterworth filter over the Chebyshev filter?
It has maximally flat response over its passband
It allows ripple in the passband in return for steeper skirts
It requires only inductors
It requires only capacitors
> The Butterworth class of filters exhibit "maximally flat response": smooth response, no passband ripple.  Their frequency response is as flat as mathematically possible in the passband, no bumps or variations (ripple) [first described by British engineer Stephen Butterworth].  The Chebyshev class of filters [in honour of Pafnuty Chebyshev, a Russian mathematician] have steeper cutoff slopes and more ripple than Butterworth filters.  Elliptic filters are sharper than the previous two.  Here is a mnemonic trick:  "The Butterworth's response is smooth as butter".
A-002-012-010    2-12-10
What is the primary advantage of the Chebyshev filter over the Butterworth filter?
It allows ripple in the passband in return for steeper skirts
It requires only capacitors
It requires only inductors
It has maximally flat response over the passband
> The Butterworth class of filters exhibit "maximally flat response": smooth response, no passband ripple.  Their frequency response is as flat as mathematically possible in the passband, no bumps or variations (ripple) [first described by British engineer Stephen Butterworth].  The Chebyshev class of filters [in honour of Pafnuty Chebyshev, a Russian mathematician] have steeper cutoff slopes and more ripple than Butterworth filters.  Elliptic filters are sharper than the previous two.  Here is a mnemonic trick:  "The Butterworth's response is smooth as butter".
A-002-012-011    2-12-11
Which of the following filter types is not suitable for use at audio and low radio frequencies?
Cavity
Elliptical
Chebyshev
Butterworth
> The quarter wavelength Resonant Cavity behaves like a very high "Q" filter.  Due to their physical size, they become practical only at VHF frequencies:  at 50 MHz (6 m), the length of the cavity is 1.5 m (one quarter wavelength).

' - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
{L03} Semiconductors.

A-002-001-001    2-1-1
What two elements widely used in semiconductor devices exhibit both metallic and non-metallic characteristics?
Silicon and germanium
Galena and germanium
Galena and bismuth
Silicon and gold
> The most basic semiconductor materials are silicon and germanium.  Atoms in metallic elements hold their peripheral electrons loosely, such materials make good conductors.  Peripheral electrons in non-metallic elements are tightly bound, such materials are insulators.  Germanium and silicon fall somewhere between the two categories but are mostly insulators when pure.  Doping with impurities increases their conductivity.
A-002-001-002    2-1-2
In what application is gallium-arsenide used as a semiconductor material in preference to germanium or silicon?
At microwave frequencies
In high-power circuits
At very low frequencies
In bipolar transistors
> Gallium arsenide (GaAs) devices can work at higher frequencies with less noise than their silicon counterparts.
A-002-001-003    2-1-3
What type of semiconductor material contains fewer free electrons than pure germanium or silicon crystals?
P-type
N-type
Bipolar type
Superconductor type
> Pure germanium and silicon are doped with impurities to produce the basic semiconductor materials.  Certain doping impurities add free electrons, forming N-Type material while others accept electrons, thus creating 'holes' found in P-Type material.
A-002-001-004    2-1-4
What type of semiconductor material contains more free electrons than pure germanium or silicon crystals?
N-type
P-type
Bipolar
Superconductor
> Pure germanium and silicon are doped with impurities to produce the basic semiconductor materials.  Certain doping impurities add free electrons, forming N-Type material while others accept electrons, thus creating 'holes' found in P-Type material.
A-002-001-005    2-1-5
What are the majority charge carriers in P-type semiconductor material?
Holes
Free electrons
Free protons
Free neutrons
> P-Type material was robbed of free electrons, positive 'holes' are the electric charge carriers.  N-Type material comprises extra electrons which serve as the electric charge carriers.
A-002-001-006    2-1-6
What are the majority charge carriers in N-type semiconductor material?
Free electrons
Holes
Free protons
Free neutrons
> N-Type material comprises extra electrons which serve as the electric charge carriers.  P-Type material was robbed of free electrons, positive 'holes' are the electric charge carriers.
A-002-001-007    2-1-7
Silicon, in its pure form, is:
an insulator
a superconductor
a semiconductor
a conductor
> The most basic semiconductor materials are silicon and germanium.  Atoms in metallic elements hold their peripheral electrons loosely, such materials make good conductors.  Peripheral electrons in non-metallic elements are tightly bound, such materials are insulators.  Germanium and silicon fall somewhere between the two categories but are mostly insulators when pure.  Doping with impurities increases their conductivity.
A-002-001-008    2-1-8
An element which is sometimes an insulator and sometimes a conductor is called a:
semiconductor
intrinsic conductor
N-type conductor
P-type conductor
> The most basic semiconductor materials are silicon and germanium.  Atoms in metallic elements hold their peripheral electrons loosely, such materials make good conductors.  Peripheral electrons in non-metallic elements are tightly bound, such materials are insulators.  Germanium and silicon fall somewhere between the two categories but are mostly insulators when pure.  Doping with impurities increases their conductivity.
A-002-001-009    2-1-9
Which of the following materials is used to make a semiconductor?
Silicon
Tantalum
Copper
Sulphur
> The most basic semiconductor materials are silicon and germanium.  Atoms in metallic elements hold their peripheral electrons loosely, such materials make good conductors.  Peripheral electrons in non-metallic elements are tightly bound, such materials are insulators.  Germanium and silicon fall somewhere between the two categories but are mostly insulators when pure.  Doping with impurities increases their conductivity.
A-002-001-010    2-1-10
Substances such as silicon in a pure state are usually good:
insulators
conductors
tuned circuits
inductors
> The most basic semiconductor materials are silicon and germanium.  Atoms in metallic elements hold their peripheral electrons loosely, such materials make good conductors.  Peripheral electrons in non-metallic elements are tightly bound, such materials are insulators.  Germanium and silicon fall somewhere between the two categories but are mostly insulators when pure.  Doping with impurities increases their conductivity.
A-002-001-011    2-1-11
A semiconductor is said to be doped when it has added to it small quantities of:
impurities
protons
ions
electrons
> Pure germanium and silicon are doped with impurities to produce the basic semiconductor materials.  Certain doping impurities add free electrons, forming N-Type material while others accept electrons, thus creating 'holes' found in P-Type material.
A-002-002-001    2-2-1
What is the principal characteristic of a Zener diode?
A constant voltage under conditions of varying current
A constant current under conditions of varying voltage
A negative resistance region
An internal capacitance that varies with the applied voltage
> Zener diodes maintain a constant voltage across a range of currents.  The Varactor (or Varicap) is a diode used under reverse bias as a "voltage-variable capacitor".  Hot-carrier (or Schottky-barrier) diodes have lower forward voltage and good high-frequency response:  their speed make them useful in Very High Frequency mixers or detectors;  in power circuits, they are excellent rectifiers in switching power supplies.  PIN diodes (with a layer of undoped or lightly doped 'intrinsic' silicon between the P and N regions) are used as switches or attenuators.
A-002-002-002    2-2-2
What type of semiconductor diode varies its internal capacitance as the voltage applied to its terminals varies?
Varactor
Zener
Silicon-controlled rectifier
Hot-carrier (Schottky)
> Zener diodes maintain a constant voltage across a range of currents.  The Varactor (or Varicap) is a diode used under reverse bias as a "voltage-variable capacitor".  Hot-carrier (or Schottky-barrier) diodes have lower forward voltage and good high-frequency response:  their speed make them useful in Very High Frequency mixers or detectors;  in power circuits, they are excellent rectifiers in switching power supplies.  PIN diodes (with a layer of undoped or lightly doped 'intrinsic' silicon between the P and N regions) are used as switches or attenuators.
A-002-002-003    2-2-3
What is a common use for the hot-carrier (Schottky) diode?
As VHF and UHF mixers and detectors
As balanced mixers in FM generation
As a variable capacitance in an automatic frequency control (AFC) circuit
As a constant voltage reference in a power supply
> Zener diodes maintain a constant voltage across a range of currents.  The Varactor (or Varicap) is a diode used under reverse bias as a "voltage-variable capacitor".  Hot-carrier (or Schottky-barrier) diodes have lower forward voltage and good high-frequency response:  their speed make them useful in Very High Frequency mixers or detectors;  in power circuits, they are excellent rectifiers in switching power supplies.  PIN diodes (with a layer of undoped or lightly doped 'intrinsic' silicon between the P and N regions) are used as switches or attenuators.
A-002-002-004    2-2-4
What limits the maximum forward current in a junction diode?
Junction temperature
Forward voltage
Back EMF
Peak inverse voltage
> Diodes conduct in one direction only:  under forward bias, maximum forward current is limited by acceptable junction temperature.  The voltage drop across the junction (volts) multiplied by the forward current (amperes) gives rise to heat dissipation (watts).  Surviving a reverse bias is determined by the Peak Inverse Voltage (PIV) rating.
A-002-002-005    2-2-5
What are the major ratings for junction diodes?
Maximum forward current and peak inverse voltage (PIV)
Maximum reverse current and capacitance
Maximum forward current and capacitance
Maximum reverse current and peak inverse voltage (PIV)
> Diodes conduct in one direction only:  under forward bias, maximum forward current is limited by acceptable junction temperature.  The voltage drop across the junction (volts) multiplied by the forward current (amperes) gives rise to heat dissipation (watts).  Surviving a reverse bias is determined by the Peak Inverse Voltage (PIV) rating.
A-002-002-006    2-2-6
Structurally, what are the two main categories of semiconductor diodes?
Junction and point contact
Vacuum and point contact
Electrolytic and point contact
Electrolytic and junction
> Point-contact diodes, where a small metal whisker touches the semiconductor material, exhibit low capacitance and serve as RF detectors or UHF mixers.  Junction diodes are formed with adjacent blocks of P and N material;  these are usable from DC to microwave.
A-002-002-007    2-2-7
What is a common use for point contact diodes?
As an RF detector
As a constant current source
As a constant voltage source
As a high voltage rectifier
> Point-contact diodes, where a small metal whisker touches the semiconductor material, exhibit low capacitance and serve as RF detectors or UHF mixers.  Junction diodes are formed with adjacent blocks of P and N material;  these are usable from DC to microwave.
A-002-002-008    2-2-8
What is one common use for PIN diodes?
As an RF switch
As a constant current source
As a high voltage rectifier
As a constant voltage source
> Zener diodes maintain a constant voltage across a range of currents.  The Varactor (or Varicap) is a diode used under reverse bias as a "voltage-variable capacitor".  Hot-carrier (or Schottky-barrier) diodes have lower forward voltage and good high-frequency response:  their speed make them useful in Very High Frequency mixers or detectors;  in power circuits, they are excellent rectifiers in switching power supplies.  PIN diodes (with a layer of undoped or lightly doped 'intrinsic' silicon between the P and N regions) are used as switches or attenuators.
A-002-002-009    2-2-9
A Zener diode is a device used to:
regulate voltage
dissipate voltage
decrease current
increase current
> Zener diodes maintain a constant voltage across a range of currents.  The Varactor (or Varicap) is a diode used under reverse bias as a "voltage-variable capacitor".  Hot-carrier (or Schottky-barrier) diodes have lower forward voltage and good high-frequency response:  their speed make them useful in Very High Frequency mixers or detectors;  in power circuits, they are excellent rectifiers in switching power supplies.  PIN diodes (with a layer of undoped or lightly doped 'intrinsic' silicon between the P and N regions) are used as switches or attenuators.
A-002-002-010    2-2-10
If a Zener diode rated at 10 V and 50 watts was operated at maximum dissipation rating, it would conduct ____ amperes:
5
50
0.05
0.5
> P = E times I.  Watts = volts times amperes.  Thus, I = P divided by E:  50 watts divided by 10 volts = 5 amperes.
A-002-002-011    2-2-11
The power-handling capability of most Zener diodes is rated at 25 degrees C or approximately room temperature. If the temperature is increased, the power handling capability is:
less
the same
much greater
slightly greater
> Heat flows from hot to cold.  If ambient temperature is higher, less heat can be drained from the junction, the junction will reach maximum safe operating temperature quicker.
A-002-003-001    2-3-1
What is the alpha of a bipolar transistor?
The change of collector current with respect to emitter current
The change of collector current with respect to base current
The change of base current with respect to collector current
The change of collector current with respect to gate current
> In a 'common base' configuration where the Emitter is the input and the Collector is the output, the Alpha factor (or common base forward current transfer ratio) is a ratio of a change in Collector current to the corresponding change in Emitter current.  In a 'common emitter' configuration where the Base is the input and the Collector is the output, the Beta factor (or common emitter forward current gain) is a ratio of a change in Collector current to a given change in Base current.  The Beta factor applies equally to a Common Collector configuration where the Base is also the input.
A-002-003-002    2-3-2
What is the beta of a bipolar transistor?
The change of collector current with respect to base current
The change of base current with respect to emitter current
The change of collector current with respect to emitter current
The change of base current with respect to gate current
> In a 'common base' configuration where the Emitter is the input and the Collector is the output, the Alpha factor (or common base forward current transfer ratio) is a ratio of a change in Collector current to the corresponding change in Emitter current.  In a 'common emitter' configuration where the Base is the input and the Collector is the output, the Beta factor (or common emitter forward current gain) is a ratio of a change in Collector current to a given change in Base current.  The Beta factor applies equally to a Common Collector configuration where the Base is also the input.
A-002-003-003    2-3-3
Which component conducts electricity from a negative emitter to a positive collector when its base voltage is made positive?
An NPN transistor
A varactor
A triode vacuum tube
A PNP transistor
> The terms Emitter, Collector and Base refer to bipolar transistors, of which there are two types:  NPN and PNP.  The Base-Emitter junction must be forward-biased for Base current to exist.  A positive voltage on the Base supposes P material for conduction to take place, the 'sandwich' is thus NPN.  Inversely, a negative Base voltage relates to a PNP.
A-002-003-004    2-3-4
What is the alpha of a bipolar transistor in common base configuration?
Forward current gain
Forward voltage gain
Reverse current gain
Reverse voltage gain
> The Alpha being a number smaller than 1, many authors refer to it as the "common base forward current transfer ratio" rather than a gain.  In a 'common base' configuration where the Emitter is the input and the Collector is the output, the Alpha factor (or common base forward current transfer ratio) is a ratio of a change in Collector current to the corresponding change in Emitter current.  In a 'common emitter' configuration where the Base is the input and the Collector is the output, the Beta factor (or common emitter forward current gain) is a ratio of a change in Collector current to a given change in Base current.  The Beta factor applies equally to a Common Collector configuration where the Base is also the input.
A-002-003-005    2-3-5
In a bipolar transistor, the change of collector current with respect to base current is called:
beta
gamma
delta
alpha
> In a 'common base' configuration where the Emitter is the input and the Collector is the output, the Alpha factor (or common base forward current transfer ratio) is a ratio of a change in Collector current to the corresponding change in Emitter current.  In a 'common emitter' configuration where the Base is the input and the Collector is the output, the Beta factor (or common emitter forward current gain) is a ratio of a change in Collector current to a given change in Base current.  The Beta factor applies equally to a Common Collector configuration where the Base is also the input.
A-002-003-006    2-3-6
The alpha of a bipolar transistor is specified for what configuration?
Common base
Common collector
Common gate
Common emitter
> In a 'common base' configuration where the Emitter is the input and the Collector is the output, the Alpha factor (or common base forward current transfer ratio) is a ratio of a change in Collector current to the corresponding change in Emitter current.  In a 'common emitter' configuration where the Base is the input and the Collector is the output, the Beta factor (or common emitter forward current gain) is a ratio of a change in Collector current to a given change in Base current.  The Beta factor applies equally to a Common Collector configuration where the Base is also the input.
A-002-003-007    2-3-7
The beta of a bipolar transistor is specified for what configurations?
Common emitter or common collector
Common emitter or common gate
Common base or common collector
Common base or common emitter
> In a 'common base' configuration where the Emitter is the input and the Collector is the output, the Alpha factor (or common base forward current transfer ratio) is a ratio of a change in Collector current to the corresponding change in Emitter current.  In a 'common emitter' configuration where the Base is the input and the Collector is the output, the Beta factor (or common emitter forward current gain) is a ratio of a change in Collector current to a given change in Base current.  The Beta factor applies equally to a Common Collector configuration where the Base is also the input.
A-002-003-008    2-3-8
Which component conducts electricity from a positive emitter to a negative collector when its base is made negative?
A PNP transistor
A triode vacuum tube
A varactor
An NPN transistor
> The terms Emitter, Collector and Base refer to bipolar transistors, of which there are two types:  NPN and PNP.  The Base-Emitter junction must be forward-biased for Base current to exist.  A positive voltage on the Base supposes P material for conduction to take place, the 'sandwich' is thus NPN.  Inversely, a negative Base voltage relates to a PNP.
A-002-003-009    2-3-9
Alpha of a bipolar transistor is equal to:
beta / (1 + beta)
beta x (1 + beta)
beta x (1 - beta)
beta / (1 - beta)
> Alpha ('common base') is always a number lesser than 1  ( the Emitter current is necessarily larger than the Collector current because the Base current also flows through the Emitter ).  Beta ('common emitter') is normally a number greater than 10 ( the Collector current is always several times the Base current ).  The Alpha is equal to Beta divided by 1 plus Beta.  The Beta is equal to Alpha divided by 1 minus Alpha.
A-002-003-010    2-3-10
The current gain of a bipolar transistor in common emitter or common collector compared to common base configuration is:
high to very high
very low
usually about double
usually about half
> Alpha ('common base') is always a number lesser than 1  ( the Emitter current is necessarily larger than the Collector current because the Base current also flows through the Emitter ).  Beta ('common emitter') is normally a number greater than 10 ( the Collector current is always several times the Base current ).  The Alpha is equal to Beta divided by 1 plus Beta.  The Beta is equal to Alpha divided by 1 minus Alpha.
A-002-003-011    2-3-11
Beta of a bipolar transistor is equal to:
alpha / (1 - alpha)
alpha / (1 + alpha)
alpha x (1 - alpha)
alpha x (1 + alpha)
> Alpha ('common base') is always a number lesser than 1  ( the Emitter current is necessarily larger than the Collector current because the Base current also flows through the Emitter ).  Beta ('common emitter') is normally a number greater than 10 ( the Collector current is always several times the Base current ).  The Alpha is equal to Beta divided by 1 plus Beta.  The Beta is equal to Alpha divided by 1 minus Alpha.
A-002-004-001    2-4-1
What is an enhancement-mode FET?
An FET without a channel  no current occurs with zero gate voltage
An FET with a channel that blocks voltage through the gate
An FET with a channel that allows current when the gate voltage is zero
An FET without a channel to hinder current through the gate
> An Enhancement-mode Insulated Gate Field Effect Transistor (IGFET) is constructed without a channel.  There is no Drain current with zero Gate voltage.  A voltage applied to the gate leads to the creation of a channel.  A forward bias on the gate heightens the concentration of charge carriers which, in turn, 'enhances' conduction.  A Depletion-mode Insulated Gate Field Effect Transistor has a channel.  Drain current is possible even without a Gate voltage.  A reverse bias on the Gate depletes charge carriers in the channel, thus reducing Drain current.  A forward bias on the Gate can make the channel even more conductive.
A-002-004-002    2-4-2
What is a depletion-mode FET?
An FET that has a channel with no gate voltage applied  a current flows with zero gate voltage
An FET without a channel  no current flows with zero gate voltage
An FET without a channel to hinder current through the gate
An FET that has a channel that blocks current when the gate voltage is zero
> An Enhancement-mode Insulated Gate Field Effect Transistor (IGFET) is constructed without a channel.  There is no Drain current with zero Gate voltage.  A voltage applied to the gate leads to the creation of a channel.  A forward bias on the gate heightens the concentration of charge carriers which, in turn, 'enhances' conduction.  A Depletion-mode Insulated Gate Field Effect Transistor has a channel.  Drain current is possible even without a Gate voltage.  A reverse bias on the Gate depletes charge carriers in the channel, thus reducing Drain current.  A forward bias on the Gate can make the channel even more conductive.
A-002-004-003    2-4-3
Why do many MOSFET devices have built-in gate protective Zener diodes?
The gate-protective Zener diode prevents the gate insulation from being punctured by small static charges or excessive voltages
The gate-protective Zener diode keeps the gate voltage within specifications to prevent the device from overheating
The gate-protective Zener diode protects the substrate from excessive voltages
The gate-protective Zener diode provides a voltage reference to provide the correct amount of reverse-bias gate voltage
> The Gate in an Insulated Gate Field Effect Transistor (IGFET or metal-oxide-semiconductor FET, MOSFET) is insulated from the channel by a thin oxide layer.  Static electricity or excessive voltage can easily destroy the dielectric layer.
A-002-004-004    2-4-4
Why are special precautions necessary in handling FET and CMOS devices?
They are susceptible to damage from static charges
They are light-sensitive
They have micro-welded semiconductor junctions that are susceptible to breakage
They have fragile leads that may break off
> The Gate in an Insulated Gate Field Effect Transistor (IGFET or metal-oxide-semiconductor FET, MOSFET) is insulated from the channel by a thin oxide layer.  Static electricity or excessive voltage can easily destroy the dielectric layer.
A-002-004-005    2-4-5
How does the input impedance of a field-effect transistor (FET) compare with that of a bipolar transistor?
An FET has high input impedance  a bipolar transistor has low input impedance
One cannot compare input impedance without knowing supply voltage
An FET has low input impedance  a bipolar transistor has high input impedance
The input impedance of FETs and bipolar transistors is the same
> Bipolar transistors are operated with a forward-biased (conductive) Base-Emitter junction.  Bipolar transistors are current amplifiers.  Impedance, as a ratio of voltage to current, is necessarily low when voltage is low and current is high.  The Field Effect Transistor, with a reverse biased Gate to channel junction, and the Insulated Gate Field Effect Transistor (IGFET or metal-oxide-semiconductor FET, MOSFET) with a Gate separated from the channel by a dielectric, are high impedance devices.
A-002-004-006    2-4-6
What are the three terminals of a junction field-effect transistor (JFET)?
Gate, drain, source
Emitter, base 1, base 2
Emitter, base, collector
Gate 1, gate 2, drain
> Remember your Basic Qualification?  The FET comprises a Source, a Gate and a Drain.  They come in two types:  N-Channel and P-Channel.
A-002-004-007    2-4-7
What are the two basic types of junction field-effect transistors (JFET)?
N-channel and P-channel
High power and low power
MOSFET and GaAsFET
Silicon and germanium
> Remember your Basic Qualification?  The FET comprises a Source, a Gate and a Drain.  They come in two types:  N-Channel and P-Channel.
A-002-004-008    2-4-8
Electron conduction in an n-channel depletion type MOSFET is associated with:
n-channel depletion
p-channel depletion
p-channel enhancement
q-channel enhancement
> This seems too simple to be true, the words in the question give the answer away.
A-002-004-009    2-4-9
Electron conduction in an n-channel enhancement MOSFET is associated with:
n-channel enhancement
q-channel depletion
p-channel enhancement
p-channel depletion
> This seems too simple to be true, the words in the question give the answer away.
A-002-004-010    2-4-10
Hole conduction in a p-channel depletion type MOSFET is associated with:
p-channel depletion
n-channel enhancement
q-channel depletion
n-channel depletion
> This seems too simple to be true, the words in the question give the answer away.
A-002-004-011    2-4-11
Hole conduction in a p-channel enhancement type MOSFET is associated with:
p-channel enhancement
n-channel depletion
n-channel enhancement
q-channel depletion
> This seems too simple to be true, the words in the question give the answer away.
A-002-005-001    2-5-1
What are the three terminals of a silicon controlled rectifier (SCR)?
Anode, cathode and gate
Gate, base 1 and base 2
Base, collector and emitter
Gate, source and sink
> The SCR, part of the Thyristor family, is made of four layers of alternating P and N type material, namely PNPN.  It comprises three electrodes:  Anode, Gate and Cathode.  As can be expected, the two outermost electrodes, the Anode and the Cathode are respectively type P and type N material.  Without gate current, the SCR looks like a regular non-conducting junction diode.  Once triggered via the Gate, the SCR resembles a forward-biased (conducting) junction diode.  Conduction continues unless current falls below a critical level.  One typical application is an overvoltage protection circuit in a power supply.
A-002-005-002    2-5-2
What are the two stable operating conditions of a silicon controlled rectifier (SCR)?
Conducting and non-conducting
Forward conducting and reverse conducting
NPN conduction and PNP conduction
Oscillating and quiescent
> The SCR, part of the Thyristor family, is made of four layers of alternating P and N type material, namely PNPN.  It comprises three electrodes:  Anode, Gate and Cathode.  As can be expected, the two outermost electrodes, the Anode and the Cathode are respectively type P and type N material.  Without gate current, the SCR looks like a regular non-conducting junction diode.  Once triggered via the Gate, the SCR resembles a forward-biased (conducting) junction diode.  Conduction continues unless current falls below a critical level.  One typical application is an overvoltage protection circuit in a power supply.
A-002-005-003    2-5-3
When a silicon controlled rectifier (SCR) is triggered, to what other semiconductor diode are its electrical characteristics similar (as measured between its cathode and anode)?
The junction diode
The PIN diode
The hot-carrier (Schottky) diode
The varactor diode
> The SCR, part of the Thyristor family, is made of four layers of alternating P and N type material, namely PNPN.  It comprises three electrodes:  Anode, Gate and Cathode.  As can be expected, the two outermost electrodes, the Anode and the Cathode are respectively type P and type N material.  Without gate current, the SCR looks like a regular non-conducting junction diode.  Once triggered via the Gate, the SCR resembles a forward-biased (conducting) junction diode.  Conduction continues unless current falls below a critical level.  One typical application is an overvoltage protection circuit in a power supply.
A-002-005-004    2-5-4
Under what operating condition does a silicon controlled rectifier (SCR) exhibit electrical characteristics similar to a forward-biased silicon rectifier?
When it is gated "on"
When it is gated "off"
When it is used as a detector
During a switching transition
> The SCR, part of the Thyristor family, is made of four layers of alternating P and N type material, namely PNPN.  It comprises three electrodes:  Anode, Gate and Cathode.  As can be expected, the two outermost electrodes, the Anode and the Cathode are respectively type P and type N material.  Without gate current, the SCR looks like a regular non-conducting junction diode.  Once triggered via the Gate, the SCR resembles a forward-biased (conducting) junction diode.  Conduction continues unless current falls below a critical level.  One typical application is an overvoltage protection circuit in a power supply.
A-002-005-005    2-5-5
The silicon controlled rectifier (SCR) is what type of device?
PNPN
NPPN
PNNP
PPNN
> The SCR, part of the Thyristor family, is made of four layers of alternating P and N type material, namely PNPN.  It comprises three electrodes:  Anode, Gate and Cathode.  As can be expected, the two outermost electrodes, the Anode and the Cathode are respectively type P and type N material.  Without gate current, the SCR looks like a regular non-conducting junction diode.  Once triggered via the Gate, the SCR resembles a forward-biased (conducting) junction diode.  Conduction continues unless current falls below a critical level.  One typical application is an overvoltage protection circuit in a power supply.
A-002-005-006    2-5-6
The control element in the silicon controlled rectifier (SCR) is called the:
gate
anode
cathode
emitter
> The SCR, part of the Thyristor family, is made of four layers of alternating P and N type material, namely PNPN.  It comprises three electrodes:  Anode, Gate and Cathode.  As can be expected, the two outermost electrodes, the Anode and the Cathode are respectively type P and type N material.  Without gate current, the SCR looks like a regular non-conducting junction diode.  Once triggered via the Gate, the SCR resembles a forward-biased (conducting) junction diode.  Conduction continues unless current falls below a critical level.  One typical application is an overvoltage protection circuit in a power supply.
A-002-005-007    2-5-7
The silicon controlled rectifier (SCR) is a member of which family?
Thyristors
Phase locked loops
Varactors
Varistors
> The SCR, part of the Thyristor family, is made of four layers of alternating P and N type material, namely PNPN.  It comprises three electrodes:  Anode, Gate and Cathode.  As can be expected, the two outermost electrodes, the Anode and the Cathode are respectively type P and type N material.  Without gate current, the SCR looks like a regular non-conducting junction diode.  Once triggered via the Gate, the SCR resembles a forward-biased (conducting) junction diode.  Conduction continues unless current falls below a critical level.  One typical application is an overvoltage protection circuit in a power supply.
A-002-005-008    2-5-8
In amateur radio equipment, which is the major application for the silicon controlled rectifier (SCR)?
Power supply overvoltage "crowbar" circuit
Class C amplifier circuit
Microphone preamplifier circuit
SWR detector circuit
> The SCR, part of the Thyristor family, is made of four layers of alternating P and N type material, namely PNPN.  It comprises three electrodes:  Anode, Gate and Cathode.  As can be expected, the two outermost electrodes, the Anode and the Cathode are respectively type P and type N material.  Without gate current, the SCR looks like a regular non-conducting junction diode.  Once triggered via the Gate, the SCR resembles a forward-biased (conducting) junction diode.  Conduction continues unless current falls below a critical level.  One typical application is an overvoltage protection circuit in a power supply.
A-002-005-009    2-5-9
Which of the following devices has anode, cathode, and gate?
The silicon controlled rectifier (SCR)
The bipolar transistor
The field effect transistor
The triode vacuum tube
> The SCR, part of the Thyristor family, is made of four layers of alternating P and N type material, namely PNPN.  It comprises three electrodes:  Anode, Gate and Cathode.  As can be expected, the two outermost electrodes, the Anode and the Cathode are respectively type P and type N material.  Without gate current, the SCR looks like a regular non-conducting junction diode.  Once triggered via the Gate, the SCR resembles a forward-biased (conducting) junction diode.  Conduction continues unless current falls below a critical level.  One typical application is an overvoltage protection circuit in a power supply.
A-002-005-010    2-5-10
When it is gated "on", the silicon controlled rectifier (SCR) exhibits electrical characteristics similar to a:
forward-biased silicon rectifier
reverse-biased silicon rectifier
forward-biased PIN diode
reverse-biased hot-carrier (Schottky) diode
> The SCR, part of the Thyristor family, is made of four layers of alternating P and N type material, namely PNPN.  It comprises three electrodes:  Anode, Gate and Cathode.  As can be expected, the two outermost electrodes, the Anode and the Cathode are respectively type P and type N material.  Without gate current, the SCR looks like a regular non-conducting junction diode.  Once triggered via the Gate, the SCR resembles a forward-biased (conducting) junction diode.  Conduction continues unless current falls below a critical level.  One typical application is an overvoltage protection circuit in a power supply.
A-002-005-011    2-5-11
Which of the following is a PNPN device?
Silicon controlled rectifier (SCR)
PIN diode
Hot carrier (Schottky) diode
Zener diode
> The SCR, part of the Thyristor family, is made of four layers of alternating P and N type material, namely PNPN.  It comprises three electrodes:  Anode, Gate and Cathode.  As can be expected, the two outermost electrodes, the Anode and the Cathode are respectively type P and type N material.  Without gate current, the SCR looks like a regular non-conducting junction diode.  Once triggered via the Gate, the SCR resembles a forward-biased (conducting) junction diode.  Conduction continues unless current falls below a critical level.  One typical application is an overvoltage protection circuit in a power supply.

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{L05} Amplifiers, Mixers and Frequency Multipliers.

A-002-006-001    2-6-1
For what portion of a signal cycle does a Class A amplifier operate?
The entire cycle
Exactly 180 degrees
More than 180 degrees but less than 360 degrees
Less than 180 degrees
> Class A:  360 degrees,  best linearity, least distortion, poor efficiency [25 to 30%].  Class AB:  significantly more than 180 but less than 360 degrees, very acceptable linearity, medium efficiency [50 to 60%].  Class B:  180 degrees, acceptable linearity, medium efficiency [up to 65%].  Class C:  much less than 180 degrees, poor linearity, high distortion, best efficiency [up to 80%].  Usable with constant amplitude signals (CW,FM) where 'flywheel' effect in tank circuit maintains the waveform.  Harmonic-rich output is useful in frequency multiplier.
A-002-006-002    2-6-2
Which class of amplifier has the highest linearity and least distortion?
Class A
Class AB
Class B
Class C
> Class A:  360 degrees,  best linearity, least distortion, poor efficiency [25 to 30%].  Class AB:  significantly more than 180 but less than 360 degrees, very acceptable linearity, medium efficiency [50 to 60%].  Class B:  180 degrees, acceptable linearity, medium efficiency [up to 65%].  Class C:  much less than 180 degrees, poor linearity, high distortion, best efficiency [up to 80%].  Usable with constant amplitude signals (CW,FM) where 'flywheel' effect in tank circuit maintains the waveform.  Harmonic-rich output is useful in frequency multiplier.
A-002-006-003    2-6-3
For what portion of a cycle does a Class AB amplifier operate?
More than 180 degrees but less than 360 degrees
Exactly 180 degrees
The entire cycle
Less than 180 degrees
> Class A:  360 degrees,  best linearity, least distortion, poor efficiency [25 to 30%].  Class AB:  significantly more than 180 but less than 360 degrees, very acceptable linearity, medium efficiency [50 to 60%].  Class B:  180 degrees, acceptable linearity, medium efficiency [up to 65%].  Class C:  much less than 180 degrees, poor linearity, high distortion, best efficiency [up to 80%].  Usable with constant amplitude signals (CW,FM) where 'flywheel' effect in tank circuit maintains the waveform.  Harmonic-rich output is useful in frequency multiplier.
A-002-006-004    2-6-4
For what portion of a cycle does a Class B amplifier operate?
180 degrees
Less than 180 degrees
More than 180 degrees but less than 360 degrees
The entire cycle
> Class A:  360 degrees,  best linearity, least distortion, poor efficiency [25 to 30%].  Class AB:  significantly more than 180 but less than 360 degrees, very acceptable linearity, medium efficiency [50 to 60%].  Class B:  180 degrees, acceptable linearity, medium efficiency [up to 65%].  Class C:  much less than 180 degrees, poor linearity, high distortion, best efficiency [up to 80%].  Usable with constant amplitude signals (CW,FM) where 'flywheel' effect in tank circuit maintains the waveform.  Harmonic-rich output is useful in frequency multiplier.
A-002-006-005    2-6-5
For what portion of a signal cycle does a Class C amplifier operate?
Less than 180 degrees
More than 180 degrees but less than 360 degrees
The entire cycle
180 degrees
> Class A:  360 degrees,  best linearity, least distortion, poor efficiency [25 to 30%].  Class AB:  significantly more than 180 but less than 360 degrees, very acceptable linearity, medium efficiency [50 to 60%].  Class B:  180 degrees, acceptable linearity, medium efficiency [up to 65%].  Class C:  much less than 180 degrees, poor linearity, high distortion, best efficiency [up to 80%].  Usable with constant amplitude signals (CW,FM) where 'flywheel' effect in tank circuit maintains the waveform.  Harmonic-rich output is useful in frequency multiplier.
A-002-006-006    2-6-6
Which of the following classes of amplifier provides the highest efficiency?
Class C
Class A
Class AB
Class B
> Class A:  360 degrees,  best linearity, least distortion, poor efficiency [25 to 30%].  Class AB:  significantly more than 180 but less than 360 degrees, very acceptable linearity, medium efficiency [50 to 60%].  Class B:  180 degrees, acceptable linearity, medium efficiency [up to 65%].  Class C:  much less than 180 degrees, poor linearity, high distortion, best efficiency [up to 80%].  Usable with constant amplitude signals (CW,FM) where 'flywheel' effect in tank circuit maintains the waveform.  Harmonic-rich output is useful in frequency multiplier.
A-002-006-007    2-6-7
Which of the following classes of amplifier would provide the highest efficiency in the output stage of a CW, RTTY or FM transmitter?
Class C
Class AB
Class B
Class A
> Class A:  360 degrees,  best linearity, least distortion, poor efficiency [25 to 30%].  Class AB:  significantly more than 180 but less than 360 degrees, very acceptable linearity, medium efficiency [50 to 60%].  Class B:  180 degrees, acceptable linearity, medium efficiency [up to 65%].  Class C:  much less than 180 degrees, poor linearity, high distortion, best efficiency [up to 80%].  Usable with constant amplitude signals (CW,FM) where 'flywheel' effect in tank circuit maintains the waveform.  Harmonic-rich output is useful in frequency multiplier.
A-002-006-008    2-6-8
Which class of amplifier provides the least efficiency?
Class A
Class C
Class B
Class AB
> Class A:  360 degrees,  best linearity, least distortion, poor efficiency [25 to 30%].  Class AB:  significantly more than 180 but less than 360 degrees, very acceptable linearity, medium efficiency [50 to 60%].  Class B:  180 degrees, acceptable linearity, medium efficiency [up to 65%].  Class C:  much less than 180 degrees, poor linearity, high distortion, best efficiency [up to 80%].  Usable with constant amplitude signals (CW,FM) where 'flywheel' effect in tank circuit maintains the waveform.  Harmonic-rich output is useful in frequency multiplier.
A-002-006-009    2-6-9
Which class of amplifier has the poorest linearity and the most distortion?
Class C
Class AB
Class A
Class B
> Class A:  360 degrees,  best linearity, least distortion, poor efficiency [25 to 30%].  Class AB:  significantly more than 180 but less than 360 degrees, very acceptable linearity, medium efficiency [50 to 60%].  Class B:  180 degrees, acceptable linearity, medium efficiency [up to 65%].  Class C:  much less than 180 degrees, poor linearity, high distortion, best efficiency [up to 80%].  Usable with constant amplitude signals (CW,FM) where 'flywheel' effect in tank circuit maintains the waveform.  Harmonic-rich output is useful in frequency multiplier.
A-002-006-010    2-6-10
Which class of amplifier operates over the full cycle?
Class A
Class AB
Class B
Class C
> Class A:  360 degrees,  best linearity, least distortion, poor efficiency [25 to 30%].  Class AB:  significantly more than 180 but less than 360 degrees, very acceptable linearity, medium efficiency [50 to 60%].  Class B:  180 degrees, acceptable linearity, medium efficiency [up to 65%].  Class C:  much less than 180 degrees, poor linearity, high distortion, best efficiency [up to 80%].  Usable with constant amplitude signals (CW,FM) where 'flywheel' effect in tank circuit maintains the waveform.  Harmonic-rich output is useful in frequency multiplier.
A-002-006-011    2-6-11
Which class of amplifier operates over less than 180 degrees of the cycle?
Class C
Class AB
Class A
Class B
> Class A:  360 degrees,  best linearity, least distortion, poor efficiency [25 to 30%].  Class AB:  significantly more than 180 but less than 360 degrees, very acceptable linearity, medium efficiency [50 to 60%].  Class B:  180 degrees, acceptable linearity, medium efficiency [up to 65%].  Class C:  much less than 180 degrees, poor linearity, high distortion, best efficiency [up to 80%].  Usable with constant amplitude signals (CW,FM) where 'flywheel' effect in tank circuit maintains the waveform.  Harmonic-rich output is useful in frequency multiplier.
A-002-007-001    2-7-1
What determines the input impedance of a FET common-source amplifier?
The input impedance is essentially determined by the gate biasing network
The input impedance is essentially determined by the resistance between the source and substrate
The input impedance is essentially determined by the resistance between the source and the drain
The input impedance is essentially determined by the resistance between the drain and substrate
> The Junction FET is considered a high impedance device.  Because the Gate in a Junction FET is always reversed-biased, its input impedance is very high;  the input impedance of the whole circuit is determined by the external Gate bias resistor.  The output impedance is determined primarily by the resistor acting as a load in the Drain circuit.
A-002-007-002    2-7-2
What determines the output impedance of a FET common-source amplifier?
The output impedance is essentially determined by the drain resistor
The output impedance is essentially determined by the drain supply voltage
The output impedance is essentially determined by the gate supply voltage
The output impedance is essentially determined by the input impedance of the FET
> The Junction FET is considered a high impedance device.  Because the Gate in a Junction FET is always reversed-biased, its input impedance is very high;  the input impedance of the whole circuit is determined by the external Gate bias resistor.  The output impedance is determined primarily by the resistor acting as a load in the Drain circuit.
A-002-007-003    2-7-3
What are the advantages of a Darlington pair audio amplifier?
High gain, high input impedance and low output impedance
Mutual gain, high stability and low mutual inductance
Mutual gain, low input impedance and low output impedance
Low output impedance, high mutual impedance and low output current
> The Darlington pair cascades two direct-coupled emitter-follower stages; Beta parameters multiply one another.  The emitter follower, just like the cathode follower or the source follower features high input impedance and low output impedance.  The Darlington configuration features high gain, high input impedance and low output impedance.  "High gain" is enough to identify the correct answer.
A-002-007-004    2-7-4
In the common base amplifier, when the input and output signals are compared:
the signals are in phase
the output signal lags the input signal by 90 degrees
the output signals leads the input signal by 90 degrees
the signals are 180 degrees out of phase
> Common Emitter:  low input Z, medium output Z, 180-degrees phase shift.  Common Base:  very low input Z, high output Z, no phase shift.  Common Collector (Common Drain, Common Plate):  high input Z, low output Z, no phase shift, also known as Emitter (Source, Cathode) follower, used for isolation or impedance matching.
A-002-007-005    2-7-5
In the common base amplifier, the input impedance, when compared to the output impedance is:
very low
only slightly higher
only slightly lower
very high
> Common Emitter:  low input Z, medium output Z, 180-degrees phase shift.  Common Base:  very low input Z, high output Z, no phase shift.  Common Collector (Common Drain, Common Plate):  high input Z, low output Z, no phase shift, also known as Emitter (Source, Cathode) follower, used for isolation or impedance matching.
A-002-007-006    2-7-6
In the common emitter amplifier, when the input and output signals are compared:
the signals are 180 degrees out of phase
the output signal leads the input signal by 90 degrees
the output signal lags the input signal by 90 degrees
the signals are in phase
> Common Emitter:  low input Z, medium output Z, 180-degrees phase shift.  Common Base:  very low input Z, high output Z, no phase shift.  Common Collector (Common Drain, Common Plate):  high input Z, low output Z, no phase shift, also known as Emitter (Source, Cathode) follower, used for isolation or impedance matching.
A-002-007-007    2-7-7
In the common collector amplifier, when the input and output signals are compared:
the signals are in phase
the output signal leads the input signal by 90 degrees
the output signal lags the input signal by 90 degrees
the signals are 180 degrees out of phase
> Common Emitter:  low input Z, medium output Z, 180-degrees phase shift.  Common Base:  very low input Z, high output Z, no phase shift.  Common Collector (Common Drain, Common Plate):  high input Z, low output Z, no phase shift, also known as Emitter (Source, Cathode) follower, used for isolation or impedance matching.
A-002-007-008    2-7-8
The FET amplifier source follower circuit is another name for:
common drain circuit
common source circuit
common mode circuit
common gate circuit
> In a source follower stage, the Source constitutes the output;  the Drain, by opposition, must be tied to a common reference (a zero reference for signals):  hence the expression, common drain.
A-002-007-009    2-7-9
The FET amplifier common source circuit is similar to which of the following bipolar transistor amplifier circuits?
Common emitter
Common collector
Common base
Common mode
> Remember your Basic Qualification?  Source, Gate, Drain in the FET compare to Emitter, Base, Collector in the bipolar.
A-002-007-010    2-7-10
The FET amplifier common drain circuit is similar to which of the following bipolar transistor amplifier circuits?
Common collector
Common emitter
Common base
Common mode
> Remember your Basic Qualification?  Source, Gate, Drain in the FET compare to Emitter, Base, Collector in the bipolar.
A-002-007-011    2-7-11
The FET amplifier common gate circuit is similar to which of the following bipolar transistor amplifier circuits?
Common base
Common mode
Common collector
Common emitter
> Remember your Basic Qualification?  Source, Gate, Drain in the FET compare to Emitter, Base, Collector in the bipolar.
A-002-008-001    2-8-1
What is an operational amplifier (op-amp)?
A high-gain, direct-coupled differential amplifier whose characteristics are determined by components mounted externally
A high-gain, direct-coupled audio amplifier whose characteristics are determined by internal components of the device
An amplifier used to increase the average output of frequency modulated amateur signals to the legal limit
A program subroutine that calculates the gain of an RF amplifier
> An Operational Amplifier is a high gain, direct-coupled differential amplifier whose characteristics are determined mainly by external components.  For example, circuit gain is determined by the feedback network from output to input.  The "ideal" Op-Amp would have infinite gain, infinite bandwidth (i.e., constant gain at any frequency), infinite input impedance and zero output impedance.
A-002-008-002    2-8-2
What would be the characteristics of the ideal op-amp?
Infinite input impedance, zero output impedance, infinite gain, and flat frequency response
Zero input impedance, zero output impedance, infinite gain, and flat frequency response
Infinite input impedance, infinite output impedance, infinite gain and flat frequency response
Zero input impedance, infinite output impedance, infinite gain, and flat frequency response
> An Operational Amplifier is a high gain, direct-coupled differential amplifier whose characteristics are determined mainly by external components.  For example, circuit gain is determined by the feedback network from output to input.  The "ideal" Op-Amp would have infinite gain, infinite bandwidth (i.e., constant gain at any frequency), infinite input impedance and zero output impedance.
A-002-008-003    2-8-3
What determines the gain of a closed-loop op-amp circuit?
The external feedback network
The PNP collector load
The voltage applied to the circuit
The collector-to-base capacitance of the PNP stage
> An Operational Amplifier is a high gain, direct-coupled differential amplifier whose characteristics are determined mainly by external components.  For example, circuit gain is determined by the feedback network from output to input.  The "ideal" Op-Amp would have infinite gain, infinite bandwidth (i.e., constant gain at any frequency), infinite input impedance and zero output impedance.
A-002-008-004    2-8-4
What is meant by the term op-amp offset voltage?
The potential between the amplifier input terminals of the op-amp in a closed-loop condition
The difference between the output voltage of the op-amp and the input voltage required for the next stage
The potential between the amplifier input terminals of the op-amp in an open-loop condition
The output voltage of the op-amp minus its input voltage
> "Offset voltage is the potential between the amplifier input terminals in the closed-loop condition.  Ideally, this voltage would be zero.  Offset results from imbalance between the differential input transistors (ARRL Handbook)".
A-002-008-005    2-8-5
What is the input impedance of a theoretically ideal op-amp?
Very high
Very low
Exactly 100 ohms
Exactly 1000 ohms
> An Operational Amplifier is a high gain, direct-coupled differential amplifier whose characteristics are determined mainly by external components.  For example, circuit gain is determined by the feedback network from output to input.  The "ideal" Op-Amp would have infinite gain, infinite bandwidth (i.e., constant gain at any frequency), infinite input impedance and zero output impedance.
A-002-008-006    2-8-6
What is the output impedance of a theoretically ideal op-amp?
Very low
Very high
Exactly 100 ohms
Exactly 1000 ohms
> An Operational Amplifier is a high gain, direct-coupled differential amplifier whose characteristics are determined mainly by external components.  For example, circuit gain is determined by the feedback network from output to input.  The "ideal" Op-Amp would have infinite gain, infinite bandwidth (i.e., constant gain at any frequency), infinite input impedance and zero output impedance.
A-002-008-007    2-8-7
What are the advantages of using an op-amp instead of LC elements in an audio filter?
Op-amps exhibit gain rather than insertion loss
Op-amps are more rugged and can withstand more abuse than can LC elements
Op-amps are available in more styles and types than are LC elements
Op-amps are fixed at one frequency
> Inductors and Capacitors are passive components;  they inevitably introduce loss.  Op-Amps used in filter applications can provide a controlled amount of gain.  Op-Amps are commonly used in active AUDIO filter circuits;  all types of responses can be implemented (low-pass, high-pass, bandpass, band-stop, a.k.a., notch).
A-002-008-008    2-8-8
What are the principal uses of an op-amp RC active filter in amateur circuitry?
Op-amp circuits are used as audio filters for receivers
Op-amp circuits are used as low-pass filters at the output of transmitters
Op-amp circuits are used as filters for smoothing power supply output
Op-amp circuits are used as high-pass filters to block RFI at the input of receivers
> Inductors and Capacitors are passive components;  they inevitably introduce loss.  Op-Amps used in filter applications can provide a controlled amount of gain.  Op-Amps are commonly used in active AUDIO filter circuits;  all types of responses can be implemented (low-pass, high-pass, bandpass, band-stop, a.k.a., notch).
A-002-008-009    2-8-9
What is an inverting op-amp circuit?
An operational amplifier circuit connected such that the input and output signals are 180 degrees out of phase
An operational amplifier circuit connected such that the input and output signals are in phase
An operational amplifier circuit connected such that the input and output signals are 90 degrees out of phase
An operational amplifier circuit connected such that the input impedance is held to zero, while the output impedance is high
> An "inverting" Op-Amp circuit introduces a 180-degrees shift:  when the input goes up, the output comes down and vice-versa.  With the "non-inverting" Op-Amp circuit, the output is in phase with the input.
A-002-008-010    2-8-10
What is a non-inverting op-amp circuit?
An operational amplifier circuit connected such that the input and output signals are in phase
An operational amplifier circuit connected such that the input and output signals are 90 degrees out of phase
An operational amplifier circuit connected such that the input impedance is held low, and the output impedance is high
An operational amplifier circuit connected such that the input and output signals are 180 degrees out of phase
> An "inverting" Op-Amp circuit introduces a 180-degrees shift:  when the input goes up, the output comes down and vice-versa.  With the "non-inverting" Op-Amp circuit, the output is in phase with the input.
A-002-008-011    2-8-11
What term is most appropriate for a high gain, direct-coupled differential amplifier whose characteristics are determined by components mounted externally?
Operational amplifier
Difference amplifier
High gain audio amplifier
Summing amplifier
> An Operational Amplifier is a high gain, direct-coupled differential amplifier whose characteristics are determined mainly by external components.  For example, circuit gain is determined by the feedback network from output to input.  The "ideal" Op-Amp would have infinite gain, infinite bandwidth (i.e., constant gain at any frequency), infinite input impedance and zero output impedance.
A-002-009-001    2-9-1
What is the mixing process?
The combination of two signals to produce sum and difference frequencies
The elimination of noise in a wideband receiver by phase differentiation
The recovery of intelligence from a modulated signal
The elimination of noise in a wideband receiver by phase comparison
> A Mixer receives two inputs.  They combine within the Mixer to produce two new frequencies:  the sum of the inputs and the difference between the inputs.  Four frequencies are present at the output:  the sum, the difference and the two original frequencies.  If a Mixer is driven into non-linearity by excessively strong signals, spurious responses will be produced.
A-002-009-002    2-9-2
What are the principal frequencies that appear at the output of a mixer circuit?
The original frequencies and the sum and difference frequencies
1.414 and 0.707 times the input frequencies
The sum, difference and square root of the input frequencies
Two and four times the original frequency
> A Mixer receives two inputs.  They combine within the Mixer to produce two new frequencies:  the sum of the inputs and the difference between the inputs.  Four frequencies are present at the output:  the sum, the difference and the two original frequencies.  If a Mixer is driven into non-linearity by excessively strong signals, spurious responses will be produced.
A-002-009-003    2-9-3
What occurs when an excessive amount of signal energy reaches the mixer circuit?
Spurious signals are generated
Automatic limiting occurs
A beat frequency is generated
Mixer blanking occurs
> A Mixer receives two inputs.  They combine within the Mixer to produce two new frequencies:  the sum of the inputs and the difference between the inputs.  Four frequencies are present at the output:  the sum, the difference and the two original frequencies.  If a Mixer is driven into non-linearity by excessively strong signals, spurious responses will be produced.
A-002-009-004    2-9-4
In a frequency multiplier circuit, the input signal is coupled to the base of a transistor through a capacitor. A radio frequency choke is connected between the base of the transistor and ground. The capacitor is:
a DC blocking capacitor
part of the input tuned circuit
a by-pass for the circuit
part of the output tank circuit
> A capacitor used for coupling let AC signals through but blocks DC.
A-002-009-005    2-9-5
A frequency multiplier circuit must be operated in:
class C
class AB
class B
class A
> A Frequency-Multiplier stage relies on harmonics produced by a gain device operated in Class C.  The output circuit is tuned to an exact multiple of the input frequency (harmonic, typically two to four times).  If greater multiplication is required, a chain of stages will be used.
A-002-009-006    2-9-6
In a frequency multiplier circuit, an inductance (L1) and a variable capacitor (C2) are connected in series between VCC+ and ground. The collector of a transistor is connected to a tap on L1. The purpose of the variable capacitor is to:
tune L1 to the desired harmonic
by-pass RF
tune L1 to the frequency applied to the base
provide positive feedback
> A tuned circuit is present in the output of a frequency multiplier to select the desired harmonic and reject unwanted signals.
A-002-009-007    2-9-7
In a frequency multiplier circuit, an inductance (L1) and a variable capacitor (C2) are connected in series between VCC+ and ground. The collector of a transistor is connected to a tap on L1. A fixed capacitor (C3) is connected between the VCC+ side of L1 and ground. The purpose of C3 is to:
provide an RF ground at the VCC connection point of L1
form a pi filter with L1 and C2
resonate with L1
by-pass any audio components
> A capacitor between the supply and ground is a "bypass" capacitor, it serves two purposes:  it provides a low-impedance path to complete the AC circuit and it keeps AC signals out of the supply line (through which they could affect other stages).  This being a frequency multiplier, the capacitor is an RF bypass.
A-002-009-008    2-9-8
In a frequency multiplier circuit, an inductance (L1) and a variable capacitor (C2) are connected in series between VCC+ and ground. The collector of a transistor is connected to a tap on L1. C2 in conjunction with L1 operate as a:
frequency multiplier
frequency divider
voltage divider
voltage doubler
> A tuned circuit is present in the output of a frequency multiplier to select the desired harmonic and reject unwanted signals.
A-002-009-009    2-9-9
In a circuit where the components are tuned to resonate at a higher frequency than applied, the circuit is most likely a:
a frequency multiplier
a VHF/UHF amplifier
a linear amplifier
a frequency divider
> A Frequency-Multiplier stage relies on harmonics produced by a gain device operated in Class C.  The output circuit is tuned to an exact multiple of the input frequency (harmonic, typically two to four times).  If greater multiplication is required, a chain of stages will be used.
A-002-009-010    2-9-10
In a frequency multiplier circuit, an inductance (L1) and a variable capacitor (C2) are connected in series between VCC+ and ground. The collector of a transistor is connected to a tap on L1. A fixed capacitor (C3) is connected between the VCC+ side of L1 and ground. C3 is a:
RF by-pass capacitor
DC blocking capacitor
tuning capacitor
coupling capacitor
> A capacitor between the supply and ground is a "bypass" capacitor, it serves two purposes:  it provides a low-impedance path to complete the AC circuit and it keeps AC signals out of the supply line (through which they could affect other stages).  This being a frequency multiplier, the capacitor is an RF bypass.
A-002-009-011    2-9-11
What stage in a transmitter would change a 5.3-MHz input signal to 14.3 MHz?
A mixer
A linear translator
A frequency multiplier
A beat frequency oscillator
> The second frequency is not a multiple of the first, this excludes the multiplier.   A Frequency Multiplier stage relies on harmonics produced by a gain device operated in Class C.  The output circuit is tuned to an exact multiple of the input frequency (harmonic, typically two to four times).  If greater multiplication is required, a chain of stages will be used.

' --  --  --  --

A-002-011-004    2-11-4
The main advantage of a crystal oscillator over a tuned LC oscillator is:
much greater frequency stability
longer life under severe operating use
freedom from harmonic emissions
simplicity
> Piezoelectric crystals behave like tuned circuits with an extremely high "Q" ("Quality Factor", in excess of 25 000).  Their accuracy and stability are outstanding.
A-002-011-008    2-11-8
Crystals are sometimes used in a circuit which has an output close to an integral multiple of the crystal frequency. This circuit is called:
an overtone oscillator
a crystal multiplier
a crystal lattice
a crystal ladder
> Key word:  MULTIPLE.  Crystals are capable of resonance either at a fundamental frequency depending on their physical dimensions or at overtone frequencies near odd-integer multiples (3rd, 5th, 7th, etc.) of the fundamental.  In a filter, crystals are used at their fundamental frequencies;  the crystal lattice filter and the crystal ladder filter are two typical configurations.  Crystal oscillators can be designed to work on a fundamental or overtone resonance;  crystals are manufactured accordingly.
A-002-011-009    2-11-9
Which of the following properties does not apply to a crystal when used in an oscillator circuit?
High power output
Good frequency stability
Very low noise because of high Q
Good frequency accuracy
> The piezoelectric property of quartz is two-fold: apply mechanical stress to a crystal and it produces a small electrical field;  subject quartz to an electrical field and the crystal changes dimensions slightly.  Crystals are capable of resonance either at a fundamental frequency depending on their physical dimensions or at overtone frequencies near odd-integer multiples (3rd, 5th, 7th, etc.).  Piezoelectric crystals can serve as filters because of their extremely high "Q" (> 25 000) or as stable, noise-free and accurate frequency references.


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{L06} Basic Digital Techniques.

A-002-010-001    2-10-1
What is a NAND gate?
A circuit that produces a logic "0" at its output only when all inputs are logic "1"
A circuit that produces a logic "1" at its output only when all inputs are logic "1"
A circuit that produces a logic "0" at its output if some but not all of its inputs are logic "1"
A circuit that produces a logic "0" at its output only when all inputs are logic "0"
> Logic circuitry uses three main operations: "AND", "OR" and "NOT".  The "NOT" is also called negation, complement or inversion.  AND: true if both inputs are true.  NAND: AND followed by a NOT, false when both inputs are true (AND, NAND: all inputs have a desired state).  OR: true if either input is true.  NOR: OR followed by a NOT, false if either input is true (OR,NOR: at least one input has desired state).  XOR: true if both inputs are complementary.  XNOR: XOR followed by a NOT, false if both inputs are complementary (XOR,XNOR: only one input has a desired state).
A-002-010-002    2-10-2
What is an OR gate?
A circuit that produces a logic "1" at its output if any input is logic "1"
A circuit that produces a logic "0" at its output if all inputs are logic "1"
A circuit that produces logic "1" at its output if all inputs are logic "0"
A circuit that produces a logic "0" at its output if any input is logic "1"
> Logic circuitry uses three main operations: "AND", "OR" and "NOT".  The "NOT" is also called negation, complement or inversion.  AND: true if both inputs are true.  NAND: AND followed by a NOT, false when both inputs are true (AND, NAND: all inputs have a desired state).  OR: true if either input is true.  NOR: OR followed by a NOT, false if either input is true (OR,NOR: at least one input has desired state).  XOR: true if both inputs are complementary.  XNOR: XOR followed by a NOT, false if both inputs are complementary (XOR,XNOR: only one input has a desired state).
A-002-010-003    2-10-3
What is a NOR gate?
A circuit that produces a logic "0" at its output if any or all inputs are logic "1"
A circuit that produces a logic "0" at its output only if all inputs are logic "0"
A circuit that produces a logic "1" at its output only if all inputs are logic "1"
A circuit that produces a logic "1" at its output if some but not all of its inputs are logic "1"
> Logic circuitry uses three main operations: "AND", "OR" and "NOT".  The "NOT" is also called negation, complement or inversion.  AND: true if both inputs are true.  NAND: AND followed by a NOT, false when both inputs are true (AND, NAND: all inputs have a desired state).  OR: true if either input is true.  NOR: OR followed by a NOT, false if either input is true (OR,NOR: at least one input has desired state).  XOR: true if both inputs are complementary.  XNOR: XOR followed by a NOT, false if both inputs are complementary (XOR,XNOR: only one input has a desired state).
A-002-010-004    2-10-4
What is a NOT gate (also known as an INVERTER)?
A circuit that produces a logic "0" at its output when the input is logic "1"
A circuit that does not allow data transmission when its input is high
A circuit that allows data transmission only when its input is high
A circuit that produces a logic "1" at its output when the input is logic "1"
> Logic circuitry uses three main operations: "AND", "OR" and "NOT".  The "NOT" is also called negation, complement or inversion.  AND: true if both inputs are true.  NAND: AND followed by a NOT, false when both inputs are true (AND, NAND: all inputs have a desired state).  OR: true if either input is true.  NOR: OR followed by a NOT, false if either input is true (OR,NOR: at least one input has desired state).  XOR: true if both inputs are complementary.  XNOR: XOR followed by a NOT, false if both inputs are complementary (XOR,XNOR: only one input has a desired state).
A-002-010-005    2-10-5
What is an EXCLUSIVE OR gate?
A circuit that produces a logic "1" at its output when only one of the inputs is logic "1"
A circuit that produces a logic "0" at its output when only one of the inputs is logic "1"
A circuit that produces a logic "1" at its output when all of the inputs are logic "1"
A circuit that produces a logic "1" at its output when all of the inputs are logic "0"
> Logic circuitry uses three main operations: "AND", "OR" and "NOT".  The "NOT" is also called negation, complement or inversion.  AND: true if both inputs are true.  NAND: AND followed by a NOT, false when both inputs are true (AND, NAND: all inputs have a desired state).  OR: true if either input is true.  NOR: OR followed by a NOT, false if either input is true (OR,NOR: at least one input has desired state).  XOR: true if both inputs are complementary.  XNOR: XOR followed by a NOT, false if both inputs are complementary (XOR,XNOR: only one input has a desired state).
A-002-010-006    2-10-6
What is an EXCLUSIVE NOR gate?
A circuit that produces a logic "1" at its output when all of the inputs are logic "1"
A circuit that produces a logic "1" at its output when only one of the inputs is logic "0"
A circuit that produces a logic "1" at its output when only one of the inputs are logic "1"
A circuit that produces a logic "0" at its output when all of the inputs are logic "1"
> Logic circuitry uses three main operations: "AND", "OR" and "NOT".  The "NOT" is also called negation, complement or inversion.  AND: true if both inputs are true.  NAND: AND followed by a NOT, false when both inputs are true (AND, NAND: all inputs have a desired state).  OR: true if either input is true.  NOR: OR followed by a NOT, false if either input is true (OR,NOR: at least one input has desired state).  XOR: true if both inputs are complementary.  XNOR: XOR followed by a NOT, false if both inputs are complementary (XOR,XNOR: only one input has a desired state).
A-002-010-007    2-10-7
What is an AND gate?
A circuit that produces a logic "1" at its output only if all its inputs are logic "1"
A circuit that produces a logic "1" at the output if at least one input is a logic "0"
A circuit that produces a logic "1" at its output only if one of its inputs is logic "1"
A circuit that produces a logic "1" at its output if all inputs are logic "0"
> Logic circuitry uses three main operations: "AND", "OR" and "NOT".  The "NOT" is also called negation, complement or inversion.  AND: true if both inputs are true.  NAND: AND followed by a NOT, false when both inputs are true (AND, NAND: all inputs have a desired state).  OR: true if either input is true.  NOR: OR followed by a NOT, false if either input is true (OR,NOR: at least one input has desired state).  XOR: true if both inputs are complementary.  XNOR: XOR followed by a NOT, false if both inputs are complementary (XOR,XNOR: only one input has a desired state).
A-002-010-008    2-10-8
What is a flip-flop circuit?
A binary sequential logic element with two stable states
A binary sequential logic element with eight stable states
A binary sequential logic element with four stable states
A binary sequential logic element with one stable state
> The "flip-flop" is a bistable multivibrator.  The adjective "bistable" alludes to two possible stable states, set or reset.  The circuit remains in one of the two states until a change is triggered.  The terms "flip-flop" and "latch" are sometimes used interchangeably.  Simple logic gates implement Combinational Logic:  the output is determined only by the current inputs.  In Sequential Logic, the output depends on current inputs and the exact sequence of prior events.  [ Nowadays, purists will tell you that a latch follows the input levels (transparency) before a final value is locked-in;  a flip-flop captures data strictly on a clock transition (edge-triggered). ]
A-002-010-009    2-10-9
What is a bistable multivibrator?
A flip-flop
An OR gate
An AND gate
A clock
> The "flip-flop" is a bistable multivibrator.  The adjective "bistable" alludes to two possible stable states, set or reset.  The circuit remains in one of the two states until a change is triggered.  The terms "flip-flop" and "latch" are sometimes used interchangeably.  Simple logic gates implement Combinational Logic:  the output is determined only by the current inputs.  In Sequential Logic, the output depends on current inputs and the exact sequence of prior events.  [ Nowadays, purists will tell you that a latch follows the input levels (transparency) before a final value is locked-in;  a flip-flop captures data strictly on a clock transition (edge-triggered). ]
A-002-010-010    2-10-10
What type of digital logic is also known as a latch?
A flip-flop
A decade counter
An OR gate
An op-amp
> The "flip-flop" is a bistable multivibrator.  The adjective "bistable" alludes to two possible stable states, set or reset.  The circuit remains in one of the two states until a change is triggered.  The terms "flip-flop" and "latch" are sometimes used interchangeably.  Simple logic gates implement Combinational Logic:  the output is determined only by the current inputs.  In Sequential Logic, the output depends on current inputs and the exact sequence of prior events.  [ Nowadays, purists will tell you that a latch follows the input levels (transparency) before a final value is locked-in;  a flip-flop captures data strictly on a clock transition (edge-triggered). ]
A-002-010-011    2-10-11
In a multivibrator circuit, when one transistor conducts, the other is:
cut off
saturated
reverse-biased
forward-biased
> The transistors in a multivibrator circuit alternate between two states:  conduction and cut-off.  The Astable multivibrator can be used as a square-wave generator.  The Monostable multivibrator assumes the alternate state for a given period when triggered.  The Bistable multivibrator is used in latch and flip-flop circuits.

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{L11} Test Equipment and measurements.

A-003-001-001    3-1-1
What is the easiest amplitude dimension to measure by viewing a pure sine wave on an oscilloscope?
Peak-to-peak voltage
Peak voltage
RMS voltage
Average voltage
> Key word:  EASIEST.  Reading the peak-to-peak amplitude of a waveform is easier than attempting to precisely center the waveform to determine the peak value.  RMS and Average values can only be computed from the peak value or peak-to-peak values.
A-003-001-002    3-1-2
What is the RMS value of a 340 volt peak-to-peak pure sine wave?
120 volts
170 volts
240 volts
300 volts
> Peak is half the peak-to-peak.  RMS (or effective) is 0.707 times the peak value.  340 volts divided by 2 times 0.707 = 120 volts RMS.
A-003-001-003    3-1-3
What is the equivalent to the RMS value of an AC voltage?
The AC voltage causing the same heating of a given resistor as a DC voltage of the same value
The AC voltage found by taking the square root of the peak AC voltage
The DC voltage causing the same heating of a given resistor as the peak AC voltage
The AC voltage found by taking the square root of the average AC value
> A kettle would bring the same quantity of water to a boil within the same time whether it runs on 120 volts DC or 120 volts RMS AC.
A-003-001-004    3-1-4
If the peak value of a 100 Hz sinusoidal waveform is 20 volts, the RMS value is:
14.14 volts
28.28 volts
7.07 volts
16.38 volts
> Peak is half the peak-to-peak.  RMS (or effective) is 0.707 times the peak value.  20 volts times 0.707 = 14.14 volts RMS.
A-003-001-005    3-1-5
In applying Ohm's law to AC circuits, current and voltage values are:
peak values times 0.707
average values
average values times 1.414
none of the proposed answers
> Peak is half the peak-to-peak.  RMS (or effective) is 0.707 times the peak value.
A-003-001-006    3-1-6
The effective value of a sine wave of voltage or current is:
70.7% of the maximum value
50% of the maximum value
100% of the maximum value
63.6% of the maximum value
> Peak is half the peak-to-peak.  RMS (or effective) is 0.707 times the peak value.
A-003-001-007    3-1-7
AC voltmeter scales are usually calibrated to read:
RMS voltage
peak voltage
instantaneous voltage
average voltage
> Voltmeters normally read the RMS (or effective) value;  i.e., 0.707 times the peak value.
A-003-001-008    3-1-8
An AC voltmeter is calibrated to read the:
effective value
peak-to-peak value
average value
peak value
> Voltmeters normally read the RMS (or effective) value;  i.e., 0.707 times the peak value.
A-003-001-009    3-1-9
Which AC voltage value will produce the same amount of heat as a DC voltage, when applied to the same resistance?
The RMS value
The average value
The peak value
The peak-to-peak value
> A kettle would bring the same quantity of water to a boil within the same time whether it runs on 120 volts DC or 120 volts RMS AC.
A-003-001-010    3-1-10
What is the peak-to-peak voltage of a sine wave that has an RMS voltage of 120 volts?
339.5 volts
84.8 volts
169.7 volts
204.8 volts
> Knowing that RMS is peak times 0.707, peak must be RMS divided by 0.707 .  Peak-to-peak is twice the peak value.  120 volts RMS divided by 0.707 = 170 volts peak.  170 volts peak times 2 = 340 volts peak-to-peak.
A-003-001-011    3-1-11
A sine wave of 17 volts peak is equivalent to how many volts RMS?
12 volts
24 volts
34 volts
8.5 volts
> Peak is half the peak-to-peak.  RMS (or effective) is 0.707 times the peak value.  17 volts times 0.707 = 12 volts RMS.
A-003-002-001    3-2-1
The power supplied to the antenna transmission line by a transmitter during an RF cycle at the highest crest of the modulation envelope is known as:
peak-envelope power
mean power
carrier power
full power
> Peak Envelope Power (PEP) in SSB is defined as the power during one cycle on a modulation peak.  Knowing that P = E squared divided by R, that peak voltage is half the peak-to-peak value  and  that RMS voltage is peak times 0.707 .  PEP can be computed as  ((peak voltage times 0.707) squared ) divided by R.  When given peak-to-peak, first divide by 2 to obtain peak voltage.
A-003-002-002    3-2-2
To compute one of the following, multiply the peak-envelope voltage by 0.707 to obtain the RMS value, square the result and divide by the load resistance. Which is the correct answer?
PEP
PIV
ERP
power factor
> PIV = Peak Inverse Voltage (diode rating).  ERP = Effective Radiated Power (transmit power minus line losses plus antenna gain).  Peak Envelope Power (PEP) in SSB is defined as the power during one cycle on a modulation peak.  Knowing that P = E squared divided by R, that peak voltage is half the peak-to-peak value  and  that RMS voltage is peak times 0.707 .  PEP can be computed as  ((peak voltage times 0.707) squared ) divided by R.  When given peak-to-peak, first divide by 2 to obtain peak voltage.
A-003-002-003    3-2-3
Peak-Envelope Power (PEP) for SSB transmission is:
Peak-Envelope Voltage (PEV) multiplied by 0.707, squared and divided by the load resistance
peak-voltage multiplied by peak current
equal to the RMS power
a hypothetical measurement
> Peak Envelope Power (PEP) in SSB is defined as the power during one cycle on a modulation peak.  Knowing that P = E squared divided by R, that peak voltage is half the peak-to-peak value  and  that RMS voltage is peak times 0.707 .  PEP can be computed as  ((peak voltage times 0.707) squared ) divided by R.  When given peak-to-peak, first divide by 2 to obtain peak voltage.
A-003-002-004    3-2-4
The formula to be used to calculate the power output of a transmitter into a resistor load using a voltmeter is:
P = (E exponent 2) /R
P = EI/R
P = EI cos 0
P = IR
> Peak Envelope Power (PEP) in SSB is defined as the power during one cycle on a modulation peak.  Knowing that P = E squared divided by R, that peak voltage is half the peak-to-peak value  and  that RMS voltage is peak times 0.707 .  PEP can be computed as  ((peak voltage times 0.707) squared ) divided by R.  When given peak-to-peak, first divide by 2 to obtain peak voltage.
A-003-002-005    3-2-5
How is the output Peak-Envelope Power of a transmitter calculated if an oscilloscope is used to measure the Peak-Envelope Voltage across a dummy resistive load (where PEP = Peak-Envelope Power, PEV = Peak-Envelope Voltage, Vp = peak-voltage, RL = load resistance)?
PEP = [(0.707 PEV)(0.707 PEV)] / RL
PEP = [(Vp)(Vp)] / (RL)
PEP = (Vp)(Vp)(RL)
PEP = [(1.414 PEV)(1.414 PEV)] / RL
> Peak Envelope Power (PEP) in SSB is defined as the power during one cycle on a modulation peak.  Knowing that P = E squared divided by R, that peak voltage is half the peak-to-peak value  and  that RMS voltage is peak times 0.707 .  PEP can be computed as  ((peak voltage times 0.707) squared ) divided by R.  When given peak-to-peak, first divide by 2 to obtain peak voltage.
A-003-002-006    3-2-6
What is the output PEP from a transmitter if an oscilloscope measures 200 volts peak-to-peak across a 50-ohm dummy load connected to the transmitter output?
100 watts
400 watts
1000 watts
200 watts
> Peak Envelope Power (PEP) in SSB is defined as the power during one cycle on a modulation peak.  Knowing that P = E squared divided by R, that peak voltage is half the peak-to-peak value  and  that RMS voltage is peak times 0.707 .  PEP can be computed as  ((peak voltage times 0.707) squared ) divided by R.  When given peak-to-peak, first divide by 2 to obtain peak voltage.  In this example, 200 divided by 2 = 100 volts peak ; (100 times 0.707) squared = 5000 ; 5000 divided by 50 = 100 watts PEP.
A-003-002-007    3-2-7
What is the output PEP from a transmitter if an oscilloscope measures 500 volts peak-to-peak across a 50-ohm dummy load connected to the transmitter output?
625 watts
1250 watts
2500 watts
500 watts
> Peak Envelope Power (PEP) in SSB is defined as the power during one cycle on a modulation peak.  Knowing that P = E squared divided by R, that peak voltage is half the peak-to-peak value  and  that RMS voltage is peak times 0.707 .  PEP can be computed as  ((peak voltage times 0.707) squared ) divided by R.  When given peak-to-peak, first divide by 2 to obtain peak voltage.  In this example, 500 divided by 2 = 250 volts peak ; (250 times 0.707) squared = 31 240 ; 31 240 divided by 50 = 625 watts PEP.
A-003-002-008    3-2-8
What is the output PEP of an unmodulated carrier transmitter if a wattmeter connected to the transmitter output indicates an average reading of 1060 watts?
1060 watts
2120 watts
1500 watts
530 watts
> Key word:  UNMODULATED.  This is a catch.  There would be no difference between output power and PEP in the absence of modulation.  [ With modulation, the answer would have been different.  Some wattmeters are calibrated to read peak power. ]
A-003-002-009    3-2-9
What is the output PEP from a transmitter, if an oscilloscope measures 400 volts peak-to-peak across a 50 ohm dummy load connected to the transmitter output?
400 watts
200 watts
600 watts
1000 watts
> Peak Envelope Power (PEP) in SSB is defined as the power during one cycle on a modulation peak.  Knowing that P = E squared divided by R, that peak voltage is half the peak-to-peak value  and  that RMS voltage is peak times 0.707 .  PEP can be computed as  ((peak voltage times 0.707) squared ) divided by R.  When given peak-to-peak, first divide by 2 to obtain peak voltage.  In this example, 400 divided by 2 = 200 volts peak ; (200 times 0.707) squared = 20 000 ; 20 000 divided by 50 = 400 watts PEP.
A-003-002-010    3-2-10
What is the output PEP from a transmitter, if an oscilloscope measures 800 volts peak-to-peak across a 50 ohm dummy load connected to the transmitter output?
1600 watts
800 watts
6400 watts
3200 watts
> Peak Envelope Power (PEP) in SSB is defined as the power during one cycle on a modulation peak.  Knowing that P = E squared divided by R, that peak voltage is half the peak-to-peak value  and  that RMS voltage is peak times 0.707 .  PEP can be computed as  ((peak voltage times 0.707) squared ) divided by R.  When given peak-to-peak, first divide by 2 to obtain peak voltage.  In this example, 800 divided by 2 = 400 volts peak ; (400 times 0.707) squared = 80 000 ; 80 000 divided by 50 = 1600 watts PEP.
A-003-002-011    3-2-11
An oscilloscope measures 500 volts peak-to-peak across a 50 ohm dummy load connected to the transmitter output during unmodulated carrier conditions. What would an average-reading power meter indicate under the same transmitter conditions?
625 watts
427.5 watts
884 watts
442 watts
> Peak Envelope Power (PEP) in SSB is defined as the power during one cycle on a modulation peak.  Knowing that P = E squared divided by R, that peak voltage is half the peak-to-peak value  and  that RMS voltage is peak times 0.707 .  PEP can be computed as  ((peak voltage times 0.707) squared ) divided by R.  When given peak-to-peak, first divide by 2 to obtain peak voltage.  In this example, 500 divided by 2 = 250 volts peak ; (250 times 0.707) squared = 31 240 ; 31 240 divided by 50 = 625 watts PEP.
A-003-003-001    3-3-1
What is a dip meter?
A variable frequency oscillator with metered feedback current
An SWR meter
A marker generator
A field-strength meter
> A 'Dip Meter' is an instrument incorporating a Variable Frequency Oscillator whose resonant circuit can be placed near circuits to be tested.  The oscillator's activity is monitored with a built-in meter.  When the external circuit's resonant frequency matches the oscillator's frequency, energy is absorbed and a dip is observed on the meter.  It works best on parallel-tuned circuits.  It can be used to test antenna traps and tuned circuits in static conditions (i.e., not operating).  Overcoupling, hand capacity and stray capacity all introduce errors.
A-003-003-002    3-3-2
What does a dip meter do?
It gives an indication of the resonant frequency of a circuit
It measures transmitter output power accurately
It measures field strength accurately
It measures frequency accurately
> A 'Dip Meter' is an instrument incorporating a Variable Frequency Oscillator whose resonant circuit can be placed near circuits to be tested.  The oscillator's activity is monitored with a built-in meter.  When the external circuit's resonant frequency matches the oscillator's frequency, energy is absorbed and a dip is observed on the meter.  It works best on parallel-tuned circuits.  It can be used to test antenna traps and tuned circuits in static conditions (i.e., not operating).  Overcoupling, hand capacity and stray capacity all introduce errors.
A-003-003-003    3-3-3
What two ways could a dip meter be used in an amateur station?
To measure resonant frequencies of antenna traps and to measure a tuned circuit resonant frequency
To measure antenna resonance and impedance
To measure antenna resonance and percentage modulation
To measure resonant frequency of antenna traps and percentage modulation
> A 'Dip Meter' is an instrument incorporating a Variable Frequency Oscillator whose resonant circuit can be placed near circuits to be tested.  The oscillator's activity is monitored with a built-in meter.  When the external circuit's resonant frequency matches the oscillator's frequency, energy is absorbed and a dip is observed on the meter.  It works best on parallel-tuned circuits.  It can be used to test antenna traps and tuned circuits in static conditions (i.e., not operating).  Overcoupling, hand capacity and stray capacity all introduce errors.
A-003-003-004    3-3-4
A dip meter supplies the radio frequency energy which enables you to check:
the resonant frequency of a circuit
the calibration of an absorption-type wavemeter
the impedance mismatch in a circuit
the adjustment of an inductor
> A 'Dip Meter' is an instrument incorporating a Variable Frequency Oscillator whose resonant circuit can be placed near circuits to be tested.  The oscillator's activity is monitored with a built-in meter.  When the external circuit's resonant frequency matches the oscillator's frequency, energy is absorbed and a dip is observed on the meter.  It works best on parallel-tuned circuits.  It can be used to test antenna traps and tuned circuits in static conditions (i.e., not operating).  Overcoupling, hand capacity and stray capacity all introduce errors.
A-003-003-005    3-3-5
A dip meter may not be used directly to:
measure the value of capacitance or inductance
align transmitter-tuned circuits
determine the frequency of oscillations
align receiver-tuned circuits
> Key word:  DIRECTLY.  A 'Dip Meter' cannot measure inductance or capacitance DIRECTLY but if an unknown component is first attached to a known inductance or capacitance, the unknown value can be computed once the resonant frequency of the combination is obtained.  The oscillator in a dip meter can usually be disabled to turn the instrument into an absorption wavemeter.
A-003-003-006    3-3-6
The dial calibration on the output attenuator of a signal generator:
reads accurately only when the attenuator is properly terminated
always reads the true output of the signal generator
reads twice the true output when the attenuator is properly terminated
reads half the true output when the attenuator is properly terminated
> A 'Signal Generator' is an instrument capable of producing any of a wide range of frequencies (RF frequencies for radio work).  Signal generators sometimes include a calibrated output attenuator so a given amplitude can be produced (e.g., a certain number of microvolts).  Calibration in that case is only accurate if the generator feeds a circuit with the expected impedance.  An instrument which "generates reference signals at exact frequency intervals" is a marker generator or crystal calibrator.
A-003-003-007    3-3-7
What is a signal generator?
A high-stability oscillator which can produce a wide range of frequencies and amplitudes
A low-stability oscillator which sweeps through a range of frequencies
A low-stability oscillator used to inject a signal into a circuit under test
A high-stability oscillator which generates reference signals at exact frequency intervals
> A 'Signal Generator' is an instrument capable of producing any of a wide range of frequencies (RF frequencies for radio work).  Signal generators sometimes include a calibrated output attenuator so a given amplitude can be produced (e.g., a certain number of microvolts).  Calibration in that case is only accurate if the generator feeds a circuit with the expected impedance.  An instrument which "generates reference signals at exact frequency intervals" is a marker generator or crystal calibrator.
A-003-003-008    3-3-8
A dip meter:
should be loosely coupled to the circuit under test
should be tightly coupled to the circuit under test
may be used only with series tuned circuits
accurately measures frequencies
> A 'Dip Meter' is an instrument incorporating a Variable Frequency Oscillator whose resonant circuit can be placed near circuits to be tested.  The oscillator's activity is monitored with a built-in meter.  When the external circuit's resonant frequency matches the oscillator's frequency, energy is absorbed and a dip is observed on the meter.  It works best on parallel-tuned circuits.  It can be used to test antenna traps and tuned circuits in static conditions (i.e., not operating).  Overcoupling, hand capacity and stray capacity all introduce errors.
A-003-003-009    3-3-9
Which two instruments are needed to measure FM receiver sensitivity for a 12 dB SINAD ratio (signal + noise + distortion over noise + distortion)?
Calibrated RF signal generator with FM tone modulation and total harmonic distortion (THD) analyzer
RF signal generator with FM tone modulation and a deviation meter
Oscilloscope and spectrum analyzer
Receiver noise bridge and total harmonic distortion analyser
> The SINAD (signal + noise + distortion over noise + distortion) ratio takes the SNR (signal + noise over noise ratio) one step further by including distortion. A 12 dB SINAD ratio ensures that speech remains intelligible.  Sensitivity expressed in those terms is the lowest RF level that will produce a usable message.  The RF signal generator must be calibrated so the number of microvolts is precisely determined.  Total Harmonic Distortion compares unwanted harmonic components added to the desired fundamental frequency, an audio tone in this instance.
A-003-003-010    3-3-10
The dip meter is most directly applicable to:
parallel tuned circuits
operational amplifier circuits
digital logic circuits
series tuned circuits
> A 'Dip Meter' is an instrument incorporating a Variable Frequency Oscillator whose resonant circuit can be placed near circuits to be tested.  The oscillator's activity is monitored with a built-in meter.  When the external circuit's resonant frequency matches the oscillator's frequency, energy is absorbed and a dip is observed on the meter.  It works best on parallel-tuned circuits.  It can be used to test antenna traps and tuned circuits in static conditions (i.e., not operating).  Overcoupling, hand capacity and stray capacity all introduce errors.
A-003-003-011    3-3-11
Which of the following is not a factor affecting the frequency accuracy of a dip meter?
Transmitter power output
Hand capacity
Stray capacity
Over coupling
> A 'Dip Meter' is an instrument incorporating a Variable Frequency Oscillator whose resonant circuit can be placed near circuits to be tested.  The oscillator's activity is monitored with a built-in meter.  When the external circuit's resonant frequency matches the oscillator's frequency, energy is absorbed and a dip is observed on the meter.  It works best on parallel-tuned circuits.  It can be used to test antenna traps and tuned circuits in static conditions (i.e., not operating).  Overcoupling, hand capacity and stray capacity all introduce errors.
A-003-004-001    3-4-1
What does a frequency counter do?
It makes frequency measurements
It measures frequency deviation
It generates broad-band white noise for calibration
It produces a reference frequency
> Two methods exist for determining frequency:  counting the number of cycles in a fixed time interval or counting the time interval for some integer number of input cycles.  In both cases, the instrument relies on an internal time base ( a crystal reference oscillator ).  The accuracy of the measurement depends on the accuracy and stability (short and long-term) of the time base.  Speed limitations in the logic circuitry limit the frequency range for a given instrument.
A-003-004-002    3-4-2
What factors limit the accuracy, frequency response and stability of a frequency counter?
Time base accuracy, speed of the logic, and time base stability
Time base accuracy, temperature coefficient of the logic and time base stability
Number of digits in the readout, speed of the logic, and time base stability
Number of digits in the readout, external frequency reference and temperature coefficient of the logic
> Two methods exist for determining frequency:  counting the number of cycles in a fixed time interval or counting the time interval for some integer number of input cycles.  In both cases, the instrument relies on an internal time base ( a crystal reference oscillator ).  The accuracy of the measurement depends on the accuracy and stability (short and long-term) of the time base.  Speed limitations in the logic circuitry limit the frequency range for a given instrument.
A-003-004-003    3-4-3
How can the accuracy of a frequency counter be improved?
By increasing the accuracy of the time base
By using slower digital logic
By using faster digital logic
By improving the accuracy of the frequency response
> Two methods exist for determining frequency:  counting the number of cycles in a fixed time interval or counting the time interval for some integer number of input cycles.  In both cases, the instrument relies on an internal time base ( a crystal reference oscillator ).  The accuracy of the measurement depends on the accuracy and stability (short and long-term) of the time base.  Speed limitations in the logic circuitry limit the frequency range for a given instrument.
A-003-004-004    3-4-4
If a frequency counter with a time base accuracy of +/- 0.1 PPM (parts per million) reads 146 520 000 Hz, what is the most that the actual frequency being measured could differ from that reading?
14.652 Hz
0.1 MHz
1.4652 Hz
1.4652 kHz
> The reading can be off by as much as the time base accuracy in Parts Per Million times the measured frequency in megahertz:  1 part per million is one hertz per megahertz.  [ In reality, an added error of plus or minus 1 count exists as the last digit displayed may have been rounded up or down. ]
A-003-004-005    3-4-5
If a frequency counter, with a time base accuracy of 10 PPM (parts per million) reads 146 520 000 Hz, what is the most the actual frequency being measured could differ from that reading?
1465.2 Hz
146.52 Hz
146.52 kHz
1465.2 kHz
> The reading can be off by as much as the time base accuracy in Parts Per Million times the measured frequency in megahertz:  1 part per million is one hertz per megahertz.  [ In reality, an added error of plus or minus 1 count exists as the last digit displayed may have been rounded up or down. ]
A-003-004-006    3-4-6
The clock in a frequency counter normally uses a:
crystal oscillator
self-oscillating Hartley oscillator
mechanical tuning fork
free-running multivibrator
> Two methods exist for determining frequency:  counting the number of cycles in a fixed time interval or counting the time interval for some integer number of input cycles.  In both cases, the instrument relies on an internal time base ( a crystal reference oscillator ).  The accuracy of the measurement depends on the accuracy and stability (short and long-term) of the time base.  Speed limitations in the logic circuitry limit the frequency range for a given instrument.
A-003-004-007    3-4-7
The frequency accuracy of a frequency counter is determined by:
the characteristics of the internal time-base generator
the size of the frequency counter
type of display used in the counter
the number of digits displayed
> Two methods exist for determining frequency:  counting the number of cycles in a fixed time interval or counting the time interval for some integer number of input cycles.  In both cases, the instrument relies on an internal time base ( a crystal reference oscillator ).  The accuracy of the measurement depends on the accuracy and stability (short and long-term) of the time base.  Speed limitations in the logic circuitry limit the frequency range for a given instrument.
A-003-004-008    3-4-8
Which device relies on a stable low-frequency oscillator, with harmonic output, to facilitate the frequency calibration of receiver dial settings?
Frequency-marker generator
Signal generator
Harmonic calibrator
Frequency counter
> A frequency marker generator (or crystal calibrator) is a relatively stable and precise oscillator rich in harmonics.  It is typically used to calibrate analog station receivers by providing reference signals at known intervals on the dial.  For an HF receiver, harmonics may be generated every 25, 50 or 100 kHz throughout the HF spectrum.  For microwave work, harmonics of 144 MHz are useful for 432 MHz (3x), 1296 (9x), 2304 (16x), 3456 (24x), 5760 (40x), 10368 (72x) and 24192 MHz (168x).  The "harmonic calibrator" is a bogus answer.
A-003-004-009    3-4-9
What is the traditional way of verifying the accuracy of a crystal calibrator?
Zero-beat the crystal oscillator against a standard frequency station such as WWV
Compare the oscillator with your transmitter
Use a dip-meter to determine the oscillator's fundamental frequency
Compare the oscillator with your receiver
> One way to calibrate a crystal calibrator (frequency marker generator) is to turn it on so it is heard while receiving a standard frequency station on shortwave.  "Zero beating", which can be done audibly, is bringing, through adjustment, the difference between two frequencies down to zero.  When two RF signals (calibrator and reference station) are nearly at the same frequency, they produce a heterodyne (beat) which falls in the audio range; the lower the beat note, the closer the match.
A-003-004-010    3-4-10
Out of the following oscillators, one is NOT, by itself, considered a high-stability reference:
voltage-controlled crystal oscillator (VCXO)
temperature compensated crystal oscillator (TCXO)
oven-controlled crystal oscillator (OCXO)
GPS disciplined oscillator (GPSDO)
> Key word:  NOT.  The voltage-controlled crystal oscillator (VCXO) is always part of a larger ensemble, its stability is not controlled, but can be controlled by an external circuit.  The temperature compensated crystal oscillator (TCXO) relies on a temperature sensor and some circuitry (analog or digital) to correct (compensate) the frequency.  The oven-controlled crystal oscillator (OCXO) maintains the crystal at a precise and constant temperature well above ambient temperature.  The GPS disciplined oscillator (GPSDO) uses a GPS (Global Positioning System) receiver to synchronize an oscillator with the highly accurate reference signals from the satellites.
A-003-004-011    3-4-11
You want to calibrate your station frequency reference to the WWV signal on your receiver. The resulting beat tone must be:
of a frequency as low as possible and with a period as long as possible
a combined frequency above both
the mathematical mean of both frequencies
at the highest audio frequency possible
> One way to calibrate a crystal calibrator (frequency marker generator) is to turn it on so it is heard while receiving a standard frequency station on shortwave.  "Zero beating", which can be done audibly, is bringing, through adjustment, the difference between two frequencies down to zero.  When two RF signals (calibrator and reference station) are nearly at the same frequency, they produce a heterodyne (beat) which falls in the audio range; the lower the beat note, the closer the match.  [ Station WWV broadcasts time and frequency information from Fort Collins, Colorado; it is maintained by the Physical Measurement Laboratory (PML) of the National Institute of Standards and Technology (NIST). ]
A-003-005-001    3-5-1
If a 100 Hz signal is fed to the horizontal input of an oscilloscope and a 150 Hz signal is fed to the vertical input, what type of pattern should be displayed on the screen?
A looping pattern with 3 horizontal loops, and 2 vertical loops
A rectangular pattern 100 mm wide and 150 mm high
An oval pattern 100 mm wide and 150 mm high
A looping pattern with 100 horizontal loops and 150 vertical loops
> Using the horizontal and vertical inputs on an oscilloscope, it is possible to compare the frequency of two sine waves or the phase relationship of two signals of equal frequency.  The resulting pattern is called a "Lissajous Figure".  Apply a known signal to the horizontal input.  The ratio of the number of loops on the horizontal edge to the number on the vertical edge equals the ratio of the vertical frequency Y divided by horizontal frequency X:  the number of cycles the Y frequency covers during one horizontal cycle.  [French mathematician Jules-Antoine Lissajous]
A-003-005-002    3-5-2
What factors limit the accuracy, frequency response and stability of an oscilloscope?
Accuracy of the time base and the linearity and bandwidth of the deflection amplifiers
Deflection amplifier output impedance and tube face frequency increments
Accuracy and linearity of the time base and tube face voltage increments
Tube face voltage increments and deflection amplifier voltages
> Similarly to the frequency counter, the accuracy and stability of the time base responsible for sweeping on the horizontal axis are paramount.  The top frequency is limited by the highest horizontal sweep rate and bandwidth of the horizontal and vertical deflection amplifiers.
A-003-005-003    3-5-3
How can the frequency response of an oscilloscope be improved?
By increasing the horizontal sweep rate and the vertical amplifier frequency response
By using a crystal oscillator as the time base and increasing the vertical sweep rate
By increasing the vertical sweep rate and the horizontal amplifier frequency response
By using triggered sweep and a crystal oscillator for the timebase
> Similarly to the frequency counter, the accuracy and stability of the time base responsible for sweeping on the horizontal axis are paramount.  The top frequency is limited by the highest horizontal sweep rate and bandwidth of the horizontal and vertical deflection amplifiers.
A-003-005-004    3-5-4
You can use an oscilloscope to display the input and output of a circuit at the same time by:
utilizing a dual trace oscilloscope
measuring the input on the X axis and the output on the Y axis
measuring the input on the X axis and the output on the Z axis
measuring the input on the Y axis and the output on the X axis
> A dual-trace oscilloscope has two distinct vertical channels.  They can be used to take simultaneous measurements at different points in a circuit.
A-003-005-005    3-5-5
An oscilloscope cannot be used to:
determine FM carrier deviation directly
measure frequency
measure DC voltage
determine the amplitude of complex voltage wave forms
> Measuring frequency is a matter of using the horizontal sweep rate and number of divisions to determine the period of one cycle of the waveform.  Measuring deviation requires a deviation meter.
A-003-005-006    3-5-6
The bandwidth of an oscilloscope is:
the highest frequency signal the scope can display
directly related to gain compression
indirectly related to screen persistence
a function of the time-base accuracy
> Similarly to the frequency counter, the accuracy and stability of the time base responsible for sweeping on the horizontal axis are paramount.  The top frequency is limited by the highest horizontal sweep rate and bandwidth of the horizontal and vertical deflection amplifiers.
A-003-005-007    3-5-7
When using Lissajous figures to determine phase differences, an indication of zero or 180 degrees is represented on the screen of an oscilloscope by:
a diagonal straight line
a horizontal straight line
an ellipse
a circle
> Two in-phase signals of the same frequency applied to the X and Y amplifiers will grow exactly at the same rate:  equal deflection on the X and Y create a trace at a 45 degree angle.  Ponder these X and Y values: 1 and 1, 2 and 2, 3 and 3, etc.  A precise 180 degree phase difference has a similar effect except the trace appears in the other two quadrants.  Ponder these X and Y values: 1 and -1, 2 and -2, 3 and -3, etc.  [other angles correspond to the sine function of the ratio of Y as the ellipse crosses the vertical centre axis to the maximum Y value.]
A-003-005-008    3-5-8
A 100-kHz signal is applied to the horizontal channel of an oscilloscope. A signal of unknown frequency is applied to the vertical channel. The resultant wave form has 5 loops displayed vertically and 2 loops horizontally. The unknown frequency is:
40 kHz
20 kHz
50 kHz
30 kHz
> Using the horizontal and vertical inputs on an oscilloscope, it is possible to compare the frequency of two sine waves or the phase relationship of two signals of equal frequency.  The resulting pattern is called a "Lissajous Figure".  Apply a known signal to the horizontal input.  The ratio of the number of loops on the horizontal edge to the number on the vertical edge equals the ratio of the vertical frequency Y divided by horizontal frequency X:  the number of cycles the Y frequency covers during one horizontal cycle.  In this example, the unknown frequency is two fifths the known frequency.  [French mathematician Jules-Antoine Lissajous]
A-003-005-009    3-5-9
An oscilloscope probe must be compensated:
every time the probe is used with a different oscilloscope
when measuring a sine wave
through the addition of a high-value series resistor
when measuring a signal whose frequency varies
> "Probe compensation is the process of adjusting the probe's RC network divider so that the probe maintains its attenuation ratio over the probe's rated bandwidth.  Most scopes have a square wave reference signal available on the front panel to use for compensating the probe.  You can attach the probe tip to the probe compensation terminal and connect the probe to an input of the scope.  Viewing the square wave reference signal, make the proper adjustments on the probe using a small screw driver so that the square waves on the scope screen look square" (Jae-yong Chang, Agilent Technologies).  Given that the input circuitry cannot be identical between instruments, adjustment must be made every time a high-impedance probe is used with a different scope.
A-003-005-010    3-5-10
What is the best instrument to use to check the signal quality of a CW or single-sideband phone transmitter?
An oscilloscope
A sidetone monitor
A signal tracer and an audio amplifier
A field-strength meter
> An oscilloscope of sufficient bandwidth permits visualizing the transmitter's output.  The sidetone monitor merely produces a tone when a CW transmitter is keyed.  The field-strength meter reports relative field strength in proximity to antennas.  The signal tracer permits troubleshooting audio circuitry.
A-003-005-011    3-5-11
What is the best signal source to connect to the vertical input of an oscilloscope for checking the quality of a transmitted signal?
The RF output of the transmitter through a sampling device
The RF signals of a nearby receiving antenna
The IF output of a monitoring receiver
The audio input of the transmitter
> The most accurate representation of a transmitted signal can be viewed at the RF output of a transmitter.  The correct method supposes the use of a "sampler" in the transmission line.  That way, proper impedance match is maintained, instruments are protected from large voltages and extraneous signals are minimized.
A-003-006-001    3-6-1
A meter has a full-scale deflection of 40 microamperes and an internal resistance of 96 ohms. You want it to read 0 to 1 mA. The value of the shunt to be used is:
4 ohms
24 ohms
16 ohms
40 ohms
> Extending the range of an ammeter supposes placing a shunt resistor across the meter movement to divert part of the current:  the shunt resistor = internal resistance divided by the multiplication factor from which we will first have deducted a quantity of one.  For example, making a 40 microamperes movement, with a 96 ohms internal resistance, read 1000 microamperes at full scale is a factor of 25:  the shunt = 96 ohms divided by 24 (i.e., 25 minus 1) = 4 ohms.  Method B:  you could have computed voltage across the meter as 40 times 96 = 3840 microvolts ; and then, computed the shunt resistor as 3840 microvolts divided by 960 microamperes = 4 ohms.
A-003-006-002    3-6-2
A moving-coil milliammeter having a full-scale deflection of 1 mA and an internal resistance of 0.5 ohms is to be converted to a voltmeter of 20 volts full-scale deflection. It would be necessary to insert a:
series resistance of 19 999.5 ohms
series resistance of 1 999.5 ohms
shunt resistance of 19 999.5 ohms
shunt resistance of 19.5 ohms
> Turning an ammeter into a voltmeter supposes inserting a suitable resistor in series with the instrument.  For a current of 1 milliampere to flow under 20 volts, Ohm's Law tells us that a total resistance of 20 000 ohms is required.  Subtract the internal resistance from that number and the actual series resistance needed is 19 999.5 ohms.
A-003-006-003    3-6-3
A voltmeter having a range of 150 volts and an internal resistance of 150 000 ohms is to be extended to read 750 volts. The required multiplier resistor would have a value of:
600 000 ohms
1 500 ohms
750 000 ohms
1 200 000 ohms
> Extending the range of a voltmeter supposes placing a suitable multiplier resistor in series with the instrument:  the multiplier resistance = total internal resistance times the multiplication factor from which we will first have deducted a quantity of one.  For example, to turn a 150 volts meter, with an internal resistance of 150 000 ohms, to read 750 volts full scale is an increase of 5 times:  the multiplier resistor = 150 000 times 4 (i.e., 5 minus 1) = 600 000 ohms.  Method B:  current for full-scale reading = 150 volts divided by 150 000 ohms = 1 milliampere.  The total resistance that would allow 1 milliampere under 750 volts = 750 000 ohms.  Deduct the internal resistance from this value to determine the multiplier resistor.
A-003-006-004    3-6-4
The sensitivity of an ammeter is an expression of:
the amount of current causing full-scale deflection
the resistance of the meter
the loading effect the meter will have on a circuit
the value of the shunt resistor
> Ammeter sensitivity is the current needed for a full-scale deflection.
A-003-006-005    3-6-5
Voltmeter sensitivity is usually expressed in ohms per volt. This means that a voltmeter with a sensitivity of 20 kilohms per volt would be a:
50 microampere meter
1 milliampere meter
50 milliampere meter
100 milliampere meter
> Voltmeter sensitivity in ohms per volt:  i.e., the full-scale reading times the sensitivity yields total instrument resistance.  Given total resistance, sensitivity can be computed as resistance divided by full-scale voltage reading:  e.g., a total of 150 000 ohms for a voltmeter reading 150 volts is a sensitivity of 1000 ohms per volt.  Given sensitivity, the current needed for full-scale voltmeter reading follows Ohm's Law:  e.g., a voltmeter with a sensitivity of 20 000 ohms per volt uses a 50 microampere movement ( I = 1 volt divided by 20 000 = 50 microamperes ).
A-003-006-006    3-6-6
The sensitivity of a voltmeter, whose resistance is 150 000 ohms on the 150-volt range, is:
1000 ohms per volt
100 000 ohms per volt
10 000 ohms per volt
150 ohms per volt
> Voltmeter sensitivity in ohms per volt:  i.e., the full-scale reading times the sensitivity yields total instrument resistance.  Given total resistance, sensitivity can be computed as resistance divided by full-scale voltage reading:  e.g., a total of 150 000 ohms for a voltmeter reading 150 volts is a sensitivity of 1000 ohms per volt.  Given sensitivity, the current needed for full-scale voltmeter reading follows Ohm's Law:  e.g., a voltmeter with a sensitivity of 20 000 ohms per volt uses a 50 microampere movement ( I = 1 volt divided by 20 000 = 50 microamperes ).
A-003-006-007    3-6-7
The range of a DC ammeter can easily be extended by:
connecting an external resistance in parallel with the internal resistance
connecting an external resistance in series with the internal resistance
changing the internal inductance of the meter
changing the internal capacitance of the meter to resonance
> Extending the range of an ammeter supposes placing a shunt resistor across the meter movement to divert part of the current:  the shunt resistor = internal resistance divided by the multiplication factor from which we will first have deducted a quantity of one.
A-003-006-008    3-6-8
What happens inside a multimeter when you switch it from a lower to a higher voltage range?
Resistance is added in series with the meter
Resistance is reduced in series with the meter
Resistance is reduced in parallel with the meter
Resistance is added in parallel with the meter
> Extending the range of a voltmeter supposes placing a suitable multiplier resistor in series with the instrument;  the higher the series resistance, the higher the voltage needed to obtain full-scale deflection on the meter.
A-003-006-009    3-6-9
How can the range of an ammeter be increased?
By adding resistance in parallel with the meter
By adding resistance in series with the circuit under test
By adding resistance in parallel with the circuit under test
By adding resistance in series with the meter
> Extending the range of an ammeter supposes placing a shunt resistor across the meter movement to divert part of the current:  the shunt resistor = internal resistance divided by the multiplication factor from which we will first have deducted a quantity of one.
A-003-006-010    3-6-10
Where should an RF wattmeter be connected for the most accurate readings of transmitter output power?
At the transmitter output connector
One-half wavelength from the transmitter output
One-half wavelength from the antenna feed point
At the antenna feed point
> Measuring right at the transmitter output connector removes any line losses from the measurement.
A-003-006-011    3-6-11
At what line impedance do most RF wattmeters usually operate?
50 ohms
25 ohms
100 ohms
300 ohms
> In-line RF wattmeters are designed to work with the most common Characteristic Impedance in radio work:  50 ohms.

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{L04} Power Supplies.

A-004-001-001    4-1-1
For the same transformer secondary voltage, which rectifier has the highest average output voltage?
Bridge
Half-wave
Quarter-wave
Full-wave centre-tap
> The half-wave configuration is not as efficient at rectification as the full-wave.  The real choice lies between the two full-wave alternatives:  bridge or full-wave with centre-tap.  The bridge configuration rectifies the full secondary winding voltage.  In contrast, the two-diode with centre-tapped transformer secondary only rectifies half the secondary voltage on each half-cycle.
A-004-001-002    4-1-2
In a half-wave power supply with a capacitor input filter and a load drawing little or no current, the peak inverse voltage (PIV) across the diode can reach _____ times the RMS voltage.
2.8
0.45
5.6
1.4
> During conduction, the capacitor charges up to the peak value of the waveform (1.4 times the RMS value). On the opposite half-cycle, and from the diode's standpoint, the transformer winding reaching opposite peak value (1.4 times the RMS value) adds to the capacitor charge for a total of 2.8 times the RMS value.
A-004-001-003    4-1-3
In a full-wave centre-tap power supply, regardless of load conditions, the peak inverse voltage (PIV) will be _____ times the RMS voltage:
2.8
0.636
0.707
1.4
> With the RMS voltage defined in this example as the voltage from one extremity of the secondary winding to the centre-tap, each diode is subjected to 2.8 times the RMS voltage, peak reverse voltage from half the transformer winding adds to the peak DC output as a reverse bias on the diode during non-conduction ( each diode serves as a half-wave rectifier ).
A-004-001-004    4-1-4
A full-wave bridge rectifier circuit makes use of both halves of the AC cycle, but unlike the full-wave centre-tap rectifier circuit it does not require:
a centre-tapped secondary on the transformer
any output filtering
a centre-tapped primary on the transformer
diodes across each leg of the transformer
> A four-diode bridge rectifier makes use of the full secondary winding without the need for a centre-tap.
A-004-001-005    4-1-5
For a given transformer the maximum output voltage available from a full-wave bridge rectifier circuit will be:
double that of the full-wave centre-tap rectifier
half that of the full-wave centre-tap rectifier
the same as the full-wave centre-tap rectifier
the same as the half-wave rectifier
> The discussion relates to rectification, thus DC voltage output is the criteria.  Imagine a 12 volts AC secondary with a centre tap.  A bridge rectifier across the full secondary will obviously provide twice the voltage of a full-wave centre-tap rectifier where each diode draws from half the secondary.  The bridge rectifier will also output slightly more DC voltage after filtering than a half-wave rectifier across the same full secondary.
A-004-001-006    4-1-6
The ripple frequency produced by a full-wave power supply connected to a normal household circuit is:
120 Hz
60 Hz
90 Hz
30 Hz
> Key word:  FULL-WAVE.  The two half-cycles are put to contribution.  The output goes from zero to peak and back 120 times per second.  Half-wave would be 60 hertz.
A-004-001-007    4-1-7
The ripple frequency produced by a half-wave power supply connected to a normal household circuit is:
60 Hz
90 Hz
120 Hz
30 Hz
> Key word:  HALF-WAVE.  One half-cycle only is put to contribution.  The output goes from zero to peak and back 60 times per second.  Full-wave would be 120 hertz.
A-004-001-008    4-1-8
Full-wave voltage doublers:
use both halves of an AC wave
create four times the output voltage of half-wave doublers
use less power than half-wave doublers
are used only in high-frequency power supplies
> A voltage doubler returns a DC voltage approximately twice the supplied AC voltage.  Through combinations of diodes and capacitors, both half-cycles are rectified and added together.  Two ubiquitous configurations are respectively designated as "half-wave" doubler and "full-wave" doubler.  The designation has more to do with the ripple frequency than how energy is transferred to the output.  Ripple frequency in the "full-wave" doubler is twice the supply frequency.  They can be implemented at normal line frequency or in switching power supplies.
A-004-001-009    4-1-9
What are the two major ratings that must not be exceeded for silicon-diode rectifiers used in power-supply circuits?
Peak inverse voltage and average forward current
Average power and average voltage
Capacitive reactance and avalanche voltage
Peak load impedance and peak voltage
> During conduction, the diode must support the average forward current.  Under reverse bias, the diode must support the peak inverse voltage present across it.
A-004-001-010    4-1-10
In a high voltage power supply, why should a resistor and capacitor be wired in parallel with the power-supply rectifier diodes?
To equalize voltage drops and guard against transient voltage spikes
To smooth the output waveform
To decrease the output voltage
To ensure that the current through each diode is about the same
> Parallel capacitors are used to bypass voltage spikes.  Parallel resistors across each diode in a chain of diodes equalize reverse voltage.
A-004-001-011    4-1-11
What is the output waveform of an unfiltered full-wave rectifier connected to a resistive load?
A series of pulses at twice the frequency of the AC input
A steady DC voltage
A sine wave at half the frequency of the AC input
A series of pulses at the same frequency as the AC input
> A full-wave rectifier puts both half-cycles to contribution:  pulsating direct current with 120 zero-to-peak transitions per second is produced.
A-004-002-001    4-2-1
Filter chokes are rated according to:
inductance and current-handling capacity
reactance at 1000 Hz
power loss
breakdown voltage
> Filter chokes are wired in series with the rectifier output.  The choke must support the current drawn by the load.  Its inductance influences the reduction in ripple.
A-004-002-002    4-2-2
Which of the following circuits gives the best regulation, under similar load conditions?
A full-wave rectifier with a choke input filter
A half-wave bridge rectifier with a capacitor input filter
A half-wave rectifier with a choke input filter
A full-wave rectifier with a capacitor input filter
> Regulation is the change in voltage from no-load to full-load.  The first filter element determines the classification.  Capacitor-input filters ensure high output voltage but poor regulation:  voltage soars to the peak AC value under no load and drops under load.  Capacitor-input leads to high peak rectifier current.  Choke-input filters limit the soar in voltage through counter-EMF and by opposing capacitor charge current.  Peak rectifier current is constrained but output voltage approximates the average value of the AC waveform.  Half-wave circuits have the poorest regulation.
A-004-002-003    4-2-3
The advantage of the capacitor input filter over the choke input filter is:
a higher terminal voltage output
better filtering action or smaller ripple voltage
improved voltage regulation
lower peak rectifier currents
> Regulation is the change in voltage from no-load to full-load.  The first filter element determines the classification.  Capacitor-input filters ensure high output voltage but poor regulation:  voltage soars to the peak AC value under no load and drops under load.  Capacitor-input leads to high peak rectifier current.  Choke-input filters limit the soar in voltage through counter-EMF and by opposing capacitor charge current.  Peak rectifier current is constrained but output voltage approximates the average value of the AC waveform.  Half-wave circuits have the poorest regulation.
A-004-002-004    4-2-4
With a normal load, the choke input filter will give the:
best regulated output
greatest percentage of ripple
greatest ripple frequency
highest output voltage
> Regulation is the change in voltage from no-load to full-load.  The first filter element determines the classification.  Capacitor-input filters ensure high output voltage but poor regulation:  voltage soars to the peak AC value under no load and drops under load.  Capacitor-input leads to high peak rectifier current.  Choke-input filters limit the soar in voltage through counter-EMF and by opposing capacitor charge current.  Peak rectifier current is constrained but output voltage approximates the average value of the AC waveform.  Half-wave circuits have the poorest regulation.
A-004-002-005    4-2-5
There are two types of filters in general use in a power supply. They are called:
choke input and capacitor input
choke output and capacitor output
choke input and capacitor output
choke output and capacitor input
> Regulation is the change in voltage from no-load to full-load.  The first filter element determines the classification.  Capacitor-input filters ensure high output voltage but poor regulation:  voltage soars to the peak AC value under no load and drops under load.  Capacitor-input leads to high peak rectifier current.  Choke-input filters limit the soar in voltage through counter-EMF and by opposing capacitor charge current.  Peak rectifier current is constrained but output voltage approximates the average value of the AC waveform.  Half-wave circuits have the poorest regulation.
A-004-002-006    4-2-6
The main function of the bleeder resistor in a power supply is to provide a discharge path for the capacitor in the power supply. But it may also be used for a secondary function, which is to:
improve voltage regulation
provide a ground return for the transformer
inhibit the flow of current through the supply
act as a secondary smoothing device in conjunction with the filter
> Regulation is the change in voltage from no-load to full-load.  By ensuring a certain minimum current draw on the supply, the bleeder prevents the capacitors from fully charging up to peak AC values when no external load is connected.
A-004-002-007    4-2-7
In a power supply, series chokes will:
readily pass the DC but will impede the flow of the AC component
readily pass the DC and the AC component
impede the passage of DC but will pass the AC component
impede both DC and AC
> Inductors oppose changes in current.  Stable DC current is not affected but AC ripple is minimized.
A-004-002-008    4-2-8
When using a choke input filter, a minimum current should be drawn all the time when the device is switched on. This can be accomplished by:
including a suitable bleeder resistance
utilizing a full-wave bridge rectifier circuit
placing an ammeter in the output circuit
increasing the value of the output capacitor
> Only the expected answer has an impact on DC current flowing through the filter whether an external load is connected or not.
A-004-002-009    4-2-9
In the design of a power supply, the designer must be careful of resonance effects because the ripple voltage could build up to a high value. The components that must be carefully selected are:
first choke and first capacitor
the bleeder resistor and the first choke
first capacitor and second capacitor
first choke and second capacitor
> Series resonance in the first choke and first capacitor across the rectifier may cause excessive rectifier peak current and abnormally high peak reverse voltages on the diodes.
A-004-002-010    4-2-10
Excessive rectifier peak current and abnormally high peak inverse voltages can be caused in a power supply by the filter forming a:
series resonant circuit with the first choke and first capacitor
short circuit across the bleeder
parallel resonant circuit with the first choke and second capacitor
tuned inductance in the filter choke
> Series resonance in the first choke and first capacitor across the rectifier may cause excessive rectifier peak current and abnormally high peak reverse voltages on the diodes.
A-004-002-011    4-2-11
In a properly designed choke input filter power supply, the no-load voltage across the filter capacitor will be about nine-tenths of the AC RMS voltage  yet it is advisable to use capacitors rated at the peak transformer voltage. Why is this large safety margin suggested?
Under no-load conditions and a burned-out bleeder, voltages could reach the peak transformer voltage
Resonance can be set up in the filter producing high voltages
Under heavy load, high currents and voltages are produced
Under no-load conditions, the current could reach a high level
> Inductors oppose changes in current.  If no current at all is drawn from a choke-input filter, the effect of the inductor vanishes:  no more counter-EMF or opposition to peak capacitor charging current.  Subsequent capacitors are allowed to fully charge to peak AC values.  [ nine tenths the RMS:  RMS is 0.707 times peak, average is 0.637 times peak, 0.637 is nine tenths of 0.707 ]
A-004-003-001    4-3-1
What is one characteristic of a linear electronic voltage regulator?
The conduction of a control element is varied in direct proportion to the line voltage or load current
It has a ramp voltage at its output
A pass transistor switches from its "on" state to its "off" state
The control device is switched on or off, with the duty cycle proportional to the line or load conditions
> In a 'linear' voltage regulator, a voltage higher than necessary is first produced;  this voltage is brought down through a voltage dropping component.  A regulator circuit (e.g., a Zener in a shunt configuration) may draw more or less current through a passive resistor to compensate for external changes.  The dropping element, in a series configuration, may be a tube or transistor whose conduction may be varied.  In a switching regulator, the incoming DC is switched on and off;  the on time is varied so that the average DC output is maintained regardless of current draw.
A-004-003-002    4-3-2
What is one characteristic of a switching voltage regulator?
The control device is switched on and off, with the duty cycle proportional to the line or load conditions
The conduction of a control element is varied in direct proportion to the line voltage or load current
It provides more than one output voltage
It gives a ramp voltage at its output
> In a 'linear' voltage regulator, a voltage higher than necessary is first produced;  this voltage is brought down through a voltage dropping component.  A regulator circuit (e.g., a Zener in a shunt configuration) may draw more or less current through a passive resistor to compensate for external changes.  The dropping element, in a series configuration, may be a tube or transistor whose conduction may be varied.  In a switching regulator, the incoming DC is switched on and off;  the on time is varied so that the average DC output is maintained regardless of current draw.
A-004-003-003    4-3-3
What device is typically used as a stable reference voltage in a linear voltage regulator?
A Zener diode
An SCR
A varactor diode
A junction diode
> Remember your Basic Qualification?  Zener diodes maintain a constant voltage across their terminals.
A-004-003-004    4-3-4
What type of linear regulator is used in applications requiring efficient utilization of the primary power source?
A series regulator
A shunt regulator
A constant current source
A shunt current source
> Key word:  EFFICIENT.  A linear regulator with an active series dropping device (tube or transistor) wastes less energy as dropping resistance is adjusted to whatever current is drawn.  A linear regulator with a passive dropping resistor and a control device in a shunt configuration (Zener, tube or transistor) is wasteful because a fixed amount of current is needed to maintain a given drop in voltage regardless of load current;  the device draws less when load current increases and vice-versa.  The shunt configuration may be needed if the unregulated source demands a constant load.
A-004-003-005    4-3-5
What type of linear voltage regulator is used in applications requiring a constant load on the unregulated voltage source?
A shunt regulator
A constant current source
A shunt current source
A series regulator
> Key words:  CONSTANT LOAD.  A linear regulator with an active series dropping device (tube or transistor) wastes less energy as dropping resistance is adjusted to whatever current is drawn.  A linear regulator with a passive dropping resistor and a control device in a shunt configuration (Zener, tube or transistor) is wasteful because a fixed amount of current is needed to maintain a given drop in voltage regardless of load current;  the device draws less when load current increases and vice-versa.  The shunt configuration may be needed if the unregulated source demands a constant load.
A-004-003-006    4-3-6
How is remote sensing accomplished in a linear voltage regulator?
A feedback connection to an error amplifier is made directly to the load
An error amplifier compares the input voltage to the reference voltage
A load connection is made outside the feedback loop
By wireless inductive loops
> Key word:  REMOTE.  Voltage regulation relies on comparing the output voltage to a set reference and using the error to adjust conduction in the control element of the regulator.  Sensing the voltage at the load rather than at the output terminals of the power supply compensates for losses all the way out to the load.
A-004-003-007    4-3-7
What is a three-terminal regulator?
A regulator containing a voltage reference, error amplifier, sensing resistors and transistors, and a pass element
A regulator that supplies three voltages at a constant current
A regulator containing three error amplifiers and sensing transistors
A regulator that supplies three voltages with variable current
> A three-terminal regulator is a single integrated circuit comprising a voltage reference, a comparator, an error amplifier, sensing resistors and a pass transistor.  Some include thermal shutdown, current foldback and over-voltage protection.  The three terminals are:  unregulated DC input, regulated DC output and ground.  Specifications include:  maximum output current, maximum output voltage, maximum input voltage and minimum input voltage (because a minimum voltage differential is needed to maintain regulation, the drop-out voltage).
A-004-003-008    4-3-8
In addition to an input voltage range what are the important characteristics of a three-terminal regulator?
Output voltage and maximum output current
Maximum output voltage and minimum output current
Minimum output voltage and maximum output current
Output voltage and minimum output current
> A three-terminal regulator is a single integrated circuit comprising a voltage reference, a comparator, an error amplifier, sensing resistors and a pass transistor.  Some include thermal shutdown, current foldback and over-voltage protection.  The three terminals are:  unregulated DC input, regulated DC output and ground.  Specifications include:  maximum output current, maximum output voltage, maximum input voltage and minimum input voltage (because a minimum voltage differential is needed to maintain regulation, the drop-out voltage).
A-004-003-009    4-3-9
What type of voltage regulator contains a voltage reference, error amplifier, sensing resistors and transistors, and a pass element in one package?
A three-terminal regulator
An op-amp regulator
A switching regulator
A Zener regulator
> A three-terminal regulator is a single integrated circuit comprising a voltage reference, a comparator, an error amplifier, sensing resistors and a pass transistor.  Some include thermal shutdown, current foldback and over-voltage protection.  The three terminals are:  unregulated DC input, regulated DC output and ground.  Specifications include:  maximum output current, maximum output voltage, maximum input voltage and minimum input voltage (because a minimum voltage differential is needed to maintain regulation, the drop-out voltage).
A-004-003-010    4-3-10
When extremely low ripple is required, or when the voltage supplied to the load must remain constant under conditions of large fluctuations of current and line voltage, a closed-loop amplifier is used to regulate the power supply. There are two main categories of electronic regulators. They are:
linear and switching
non-linear and switching
linear and non-linear
stiff and switching
> In a 'linear' voltage regulator, a voltage higher than necessary is first produced;  this voltage is brought down through a voltage dropping component.  A regulator circuit (e.g., a Zener in a shunt configuration) may draw more or less current through a passive resistor to compensate for external changes.  The dropping element, in a series configuration, may be a tube or transistor whose conduction may be varied.  In a switching regulator, the incoming DC is switched on and off;  the on time is varied so that the average DC output is maintained regardless of current draw.
A-004-003-011    4-3-11
A modern type of regulator, which features a reference, high-gain amplifier, temperature-compensated voltage sensing resistors and transistors as well as a pass element is commonly referred to as a:
three-terminal regulator
nine-pin regulator
twenty-four pin regulator
six-terminal regulator
> A three-terminal regulator is a single integrated circuit comprising a voltage reference, a comparator, an error amplifier, sensing resistors and a pass transistor.  Some include thermal shutdown, current foldback and over-voltage protection.  The three terminals are:  unregulated DC input, regulated DC output and ground.  Specifications include:  maximum output current, maximum output voltage, maximum input voltage and minimum input voltage (because a minimum voltage differential is needed to maintain regulation, the drop-out voltage).
A-004-004-001    4-4-1
In a series-regulated power supply, the power dissipation of the pass transistor is:
directly proportional to the load current and the input/output voltage differential
the inverse of the load current and the input/output voltage differential
dependent upon the peak inverse voltage appearing across the Zener diode
indirectly proportional to the load voltage and the input/output voltage differential
> The pass transistor is the device acting as a variable resistor to drop the unregulated DC source down to the regulated output.  Power is voltage times current:  in this case, the difference in voltage from input to output times the current drawn by the load.
A-004-004-002    4-4-2
In any regulated power supply, the output is cleanest and the regulation is best:
at the point where the sampling network or error amplifier is connected
across the secondary of the pass transistor
across the load
at the output of the pass transistor
> A voltage regulator maintains a stable output by comparing a sample of the output voltage with a reference and adjusting conduction in the pass transistor accordingly.  The corrective action is only accurate for the precise point where the measurement is taken.  Because of losses, the load itself may find itself at a lower voltage:  this is the reason for 'remote sensing' in certain applications.
A-004-004-003    4-4-3
When discussing a power supply the_______ resistance is equal to the output voltage divided by the total current drawn, including the current drawn by the bleeder resistor:
load
ideal
rectifier
differential
> Per Ohm's Law, resistance is voltage divided by current.  Output voltage and total current drawn describe the load placed on the power supply.
A-004-004-004    4-4-4
The regulation of long-term changes in the load resistance of a power supply is called:
static regulation
active regulation
analog regulation
dynamic regulation
> Key words:  LONG-TERM.  Regulation is the change in voltage from no-load to full-load.  Static regulation relates to the supply's performance in relation with long-term changes in load resistance or line variations (AC source).  Dynamic regulation is required when the current draw varies as a Morse key is pressed (CW) or with each syllable (SSB) in a final amplifier.  A large output capacitor, the last in the filter configuration, can improve dynamic regulation.
A-004-004-005    4-4-5
The regulation of short-term changes in the load resistance of a power supply is called:
dynamic regulation
static regulation
analog regulation
active regulation
> Key words:  SHORT-TERM.   Regulation is the change in voltage from no-load to full-load.  Static regulation relates to the supply's performance in relation with long-term changes in load resistance or line variations (AC source).  Dynamic regulation is required when the current draw varies as a Morse key is pressed (CW) or with each syllable (SSB) in a final amplifier.  A large output capacitor, the last in the filter configuration, can improve dynamic regulation.
A-004-004-006    4-4-6
The dynamic regulation of a power supply is improved by increasing the value of:
the output capacitor
the choke
the input capacitor
the bleeder resistor
> Regulation is the change in voltage from no-load to full-load.  Static regulation relates to the supply's performance in relation with long-term changes in load resistance or line variations (AC source).  Dynamic regulation is required when the current draw varies as a Morse key is pressed (CW) or with each syllable (SSB) in a final amplifier.  A large output capacitor, the last in the filter configuration, can improve dynamic regulation.
A-004-004-007    4-4-7
The output capacitor, in a power supply filter used to provide power for an SSB or CW transmitter, will give better dynamic regulation if:
the output capacitance is increased
the negative terminal of the electrolytic capacitor is connected to the positive and the positive terminal to ground
a battery is placed in series with the output capacitor
it is placed in series with other capacitors
> Regulation is the change in voltage from no-load to full-load.  Static regulation relates to the supply's performance in relation with long-term changes in load resistance or line variations (AC source).  Dynamic regulation is required when the current draw varies as a Morse key is pressed (CW) or with each syllable (SSB) in a final amplifier.  A large output capacitor, the last in the filter configuration, can improve dynamic regulation.
A-004-004-008    4-4-8
In a regulated power supply, four diodes connected together in a BRIDGE act as:
a rectifier
equalization across the transformer
matching between the secondary of the power transformer and the filter
a tuning network
> Four diodes in a bridge configuration permit full-wave rectification with a single secondary winding.
A-004-004-009    4-4-9
In a regulated power supply, components that conduct alternating current at the input before the transformer and direct current before the output are:
fuses
capacitors
diodes
chokes
> Only fuses can be expected to be found on either side of the transformer and pass AC or DC equally.
A-004-004-010    4-4-10
In a regulated power supply, the output of the electrolytic filter capacitor is connected to the:
voltage regulator
pi filter
solid-state by-pass circuit
matching circuit for the load
> Remember your Basic Qualification?  The Regulated Power Supply comprises:  the input, the transformer, the rectifier, the filter, the regulator and the output.
A-004-004-011    4-4-11
In a regulated power supply, a diode connected across the input and output terminals of a regulator is used to:
protect the regulator from reverse voltages
provide an RF by-pass for the voltage control
provide additional capacity
protect the regulator from voltage fluctuations in the primary of the transformer
> A fast reverse-biased diode between the output and input terminals prevents a large capacitor following the three-terminal regulator from discharging through the regulator if the input was ever short-circuited.

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{L07} Oscillators.

A-005-001-001    5-1-1
How is the positive feedback coupled to the input in a Hartley oscillator?
Through a tapped coil
Through a capacitive divider
Through link coupling
Through a neutralizing capacitor
> Hartley = a tap on the inductor of the tuned circuit permits inserting positive feedback from output to input.  Colpitts = the inductor tap of the Hartley is replaced by two series capacitors in a capacitive divider configuration.  Relatively large capacitor values, when compared to the Hartley, mean less influence from internal capacitance changes in the device, hence stability.  Pierce = derived from the Colpitts, a piezoelectric crystal replaces the tuned circuit.  Capacitive coupling maintains oscillation.
A-005-001-002    5-1-2
How is positive feedback coupled to the input in a Colpitts oscillator?
Through a capacitive divider
Through a tapped coil
Through a neutralizing capacitor
Through a link coupling
> Hartley = a tap on the inductor of the tuned circuit permits inserting positive feedback from output to input.  Colpitts = the inductor tap of the Hartley is replaced by two series capacitors in a capacitive divider configuration.  Relatively large capacitor values, when compared to the Hartley, mean less influence from internal capacitance changes in the device, hence stability.  Pierce = derived from the Colpitts, a piezoelectric crystal replaces the tuned circuit.  Capacitive coupling maintains oscillation.
A-005-001-003    5-1-3
How is positive feedback coupled to the input in a Pierce oscillator?
Through capacitive coupling
Through a neutralizing capacitor
Through link coupling
Through a tapped coil
> Hartley = a tap on the inductor of the tuned circuit permits inserting positive feedback from output to input.  Colpitts = the inductor tap of the Hartley is replaced by two series capacitors in a capacitive divider configuration.  Relatively large capacitor values, when compared to the Hartley, mean less influence from internal capacitance changes in the device, hence stability.  Pierce = derived from the Colpitts, a piezoelectric crystal replaces the tuned circuit.  Capacitive coupling maintains oscillation.
A-005-001-004    5-1-4
Why is the Colpitts oscillator circuit commonly used in a VFO?
It is stable
It can be used with or without crystal lock-in
The frequency is a linear function with load impedance
It has high output power
> Hartley = a tap on the inductor of the tuned circuit permits inserting positive feedback from output to input.  Colpitts = the inductor tap of the Hartley is replaced by two series capacitors in a capacitive divider configuration.  Relatively large capacitor values, when compared to the Hartley, mean less influence from internal capacitance changes in the device, hence stability.  Pierce = derived from the Colpitts, a piezoelectric crystal replaces the tuned circuit.  Capacitive coupling maintains oscillation.
A-005-001-005    5-1-5
Why must a very stable reference oscillator be used as part of a phase-locked loop (PLL) frequency synthesizer?
Any phase variations in the reference oscillator signal will produce phase noise in the synthesizer output
Any phase variations in the reference oscillator signal will produce harmonic distortion in the modulating signal
Any amplitude variations in the reference oscillator signal will prevent the loop from changing frequency
Any amplitude variations in the reference oscillator signal will prevent the loop from locking to the desired signal
> Key words:  PHASE-LOCKED.  As the name implies, a PLL synthesizer includes a voltage-controlled oscillator (VCO) whose output is constantly compared to a stable crystal reference.  If the phase of the output signal begins to lead or lag the reference (a phase error), a correction is applied to the oscillator tuning.  If the reference is noisy or subject to phase jitter, the output is similarly corrupted.
A-005-001-006    5-1-6
Positive feedback from a capacitive divider indicates the oscillator type is:
Colpitts
Pierce
Hartley
Miller
> Hartley = a tap on the inductor of the tuned circuit permits inserting positive feedback from output to input.  Colpitts = the inductor tap of the Hartley is replaced by two series capacitors in a capacitive divider configuration.  Relatively large capacitor values, when compared to the Hartley, mean less influence from internal capacitance changes in the device, hence stability.  Pierce = derived from the Colpitts, a piezoelectric crystal replaces the tuned circuit.  Capacitive coupling maintains oscillation.
A-005-001-007    5-1-7
In an RF oscillator circuit designed for high stability, the positive feedback is drawn from two capacitors connected in series. These two capacitors would most likely be:
silver mica
ceramic
electrolytics
Mylar
> In an oscillator, stability is paramount.   Silver Mica, NP0 (N-P-Zero, negative-positive-zero) ceramic and polystyrene capacitors are temperature-stable.  The electrolytic is suitable as a filter or audio bypass.  The plain ceramic capacitor is good for coupling or RF bypass.
A-005-001-008    5-1-8
In an oscillator circuit where positive feedback is obtained through a single capacitor in series with the crystal, the type of oscillator is:
Pierce
Colpitts
Hartley
Miller
> Hartley = a tap on the inductor of the tuned circuit permits inserting positive feedback from output to input.  Colpitts = the inductor tap of the Hartley is replaced by two series capacitors in a capacitive divider configuration.  Relatively large capacitor values, when compared to the Hartley, mean less influence from internal capacitance changes in the device, hence stability.  Pierce = derived from the Colpitts, a piezoelectric crystal replaces the tuned circuit.  Capacitive coupling maintains oscillation.
A-005-001-009    5-1-9
A circuit depending on positive feedback for its operation would be a:
variable-frequency oscillator
mixer
detector
audio amplifier
> An oscillator, fixed or variable, is an amplifier with a positive feedback path from output to input used to start and maintain oscillation.
A-005-001-010    5-1-10
An apparatus with an oscillator and a class C amplifier would be:
a two-stage CW transmitter
a fixed-frequency single-sideband transmitter
a two-stage frequency-modulated transmitter
a two-stage regenerative receiver
> A simple two-stage CW transmitter comprises an oscillator and a Class-C power amplifier.  A transformer at the output of the oscillator serves the dual purpose of tuned circuit and coupling to the next stage.  The DC supply to the final amplifier is bypassed to ground with a capacitor and decoupled through an RF choke so RF is kept out of the supply.
A-005-001-011    5-1-11
In an oscillator where positive feedback is provided through a capacitor in series with a crystal, that type of oscillator is a:
Pierce
Colpitts
Hartley
Franklin
> Hartley = a tap on the inductor of the tuned circuit permits inserting positive feedback from output to input.  Colpitts = the inductor tap of the Hartley is replaced by two series capacitors in a capacitive divider configuration.  Relatively large capacitor values, when compared to the Hartley, mean less influence from internal capacitance changes in the device, hence stability.  Pierce = derived from the Colpitts, a piezoelectric crystal replaces the tuned circuit.  Capacitive coupling maintains oscillation.

' - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
{L09} Transmitters.

A-005-002-001    5-2-1
The output tuning controls on a transmitter power amplifier with an adjustable PI network:
allow efficient transfer of power to the antenna
allow switching to different antennas
reduce the possibility of cross-modulation in adjunct receivers
are involved with frequency multiplication in the previous stage
> Tube power amplifiers always include a matching network to match the high impedance of the tube to the antenna system impedance.  As always, impedance match is all about maximum power transfer.
A-005-002-002    5-2-2
The purpose of using a centre-tap return connection on the secondary of transmitting tube's filament transformer is to:
prevent modulation of the emitted wave by the alternating current filament supply
reduce the possibility of harmonic emissions
keep the output voltage constant with a varying load
obtain optimum power output
> When the cathode is simply the filament (a "directly-heated cathode"), the voltage drop across the filament (e.g., 6.3 volts AC) is in series with the cathode DC reference voltage:  as an example, while one side of the filament might be at a certain DC voltage, the other extremity is at some other value, a value influenced by the AC voltage impressed on the filament.  Electron flow is affected by an AC variation, hum results.
A-005-002-003    5-2-3
In a grounded grid amplifier using a triode vacuum tube, the input signal is applied to:
the cathode
the plate
the control grid
the filament leads
> A grounded-grid amplifier runs with the grid at ground potential.  The cathode is above RF ground and serves as the input.  A DC bias is applied to the cathode via an RF choke.  Positive voltage (B+) is supplied to the plate via an RF choke.  The plate is the output, a blocking capacitor passes the RF out to the matching network.  A transformer provides AC filament voltage.  The heater (in an indirectly-heated cathode tube) is bypassed to ground so radiofrequency does not stray out on the filament supply lines.  [ If a tube is directly-heated (no separate cathode), filament voltage is brought through a filament choke.  The side of the choke connected to the transformer is bypassed to ground with two capacitors. ]
A-005-002-004    5-2-4
In a grounded grid amplifier using a triode vacuum tube, the plate is connected to the pi-network through a:
blocking capacitor
by-pass capacitor
tuning capacitor
electrolytic capacitor
> A grounded-grid amplifier runs with the grid at ground potential.  The cathode is above RF ground and serves as the input.  A DC bias is applied to the cathode via an RF choke.  Positive voltage (B+) is supplied to the plate via an RF choke.  The plate is the output, a blocking capacitor passes the RF out to the matching network.  A transformer provides AC filament voltage.  The heater (in an indirectly-heated cathode tube) is bypassed to ground so radiofrequency does not stray out on the filament supply lines.  [ If a tube is directly-heated (no separate cathode), filament voltage is brought through a filament choke.  The side of the choke connected to the transformer is bypassed to ground with two capacitors. ]
A-005-002-005    5-2-5
In a grounded grid amplifier using a triode vacuum tube, the plate is connected to a radio frequency choke. The other end of the radio frequency choke connects to the:
B+ (high voltage)
filament voltage
ground
B- (bias)
> A grounded-grid amplifier runs with the grid at ground potential.  The cathode is above RF ground and serves as the input.  A DC bias is applied to the cathode via an RF choke.  Positive voltage (B+) is supplied to the plate via an RF choke.  The plate is the output, a blocking capacitor passes the RF out to the matching network.  A transformer provides AC filament voltage.  The heater (in an indirectly-heated cathode tube) is bypassed to ground so radiofrequency does not stray out on the filament supply lines.  [ If a tube is directly-heated (no separate cathode), filament voltage is brought through a filament choke.  The side of the choke connected to the transformer is bypassed to ground with two capacitors. ]
A-005-002-006    5-2-6
In a grounded grid amplifier using a triode vacuum tube, the cathode is connected to a radio frequency choke. The other end of the radio frequency choke connects to the:
B- (bias)
ground
filament voltage
B+ (high voltage)
> A grounded-grid amplifier runs with the grid at ground potential.  The cathode is above RF ground and serves as the input.  A DC bias is applied to the cathode via an RF choke.  Positive voltage (B+) is supplied to the plate via an RF choke.  The plate is the output, a blocking capacitor passes the RF out to the matching network.  A transformer provides AC filament voltage.  The heater (in an indirectly-heated cathode tube) is bypassed to ground so radiofrequency does not stray out on the filament supply lines.  [ If a tube is directly-heated (no separate cathode), filament voltage is brought through a filament choke.  The side of the choke connected to the transformer is bypassed to ground with two capacitors. ]
A-005-002-007    5-2-7
In a grounded grid amplifier using a triode vacuum tube, the secondary winding of a transformer is connected directly to the vacuum tube. This transformer provides:
filament voltage
B- (bias)
B+ (high voltage)
Screen voltage
> A grounded-grid amplifier runs with the grid at ground potential.  The cathode is above RF ground and serves as the input.  A DC bias is applied to the cathode via an RF choke.  Positive voltage (B+) is supplied to the plate via an RF choke.  The plate is the output, a blocking capacitor passes the RF out to the matching network.  A transformer provides AC filament voltage.  The heater (in an indirectly-heated cathode tube) is bypassed to ground so radiofrequency does not stray out on the filament supply lines.  [ If a tube is directly-heated (no separate cathode), filament voltage is brought through a filament choke.  The side of the choke connected to the transformer is bypassed to ground with two capacitors. ]
A-005-002-008    5-2-8
In a grounded grid amplifier using a triode vacuum tube, what would be the approximate B+ voltage required for an output of 400 watts at 400 mA with approximately 50 percent efficiency?
2000 volts
500 volts
3000 volts
1000 volts
> 400 watts out at 50% efficiency supposes that 800 watts DC are needed.  Power is voltage times current ; thus, voltage is power divided by current ; 800 watts divided by 0.4 ampere = 2000 volts.
A-005-002-009    5-2-9
In a grounded grid amplifier using a triode vacuum tube, each side of the filament is connected to a capacitor whose other end is connected to ground. These are:
by-pass capacitors
tuning capacitors
electrolytic capacitors
blocking capacitors
> A grounded-grid amplifier runs with the grid at ground potential.  The cathode is above RF ground and serves as the input.  A DC bias is applied to the cathode via an RF choke.  Positive voltage (B+) is supplied to the plate via an RF choke.  The plate is the output, a blocking capacitor passes the RF out to the matching network.  A transformer provides AC filament voltage.  The heater (in an indirectly-heated cathode tube) is bypassed to ground so radiofrequency does not stray out on the filament supply lines.  [ If a tube is directly-heated (no separate cathode), filament voltage is brought through a filament choke.  The side of the choke connected to the transformer is bypassed to ground with two capacitors. ]
A-005-002-010    5-2-10
After you have opened a VHF power amplifier to make internal tuning adjustments, what should you do before you turn the amplifier on?
Be certain all amplifier shielding is fastened in place
Make sure that the power interlock switch is bypassed so you can test the amplifier
Be certain no antenna is attached so that you will not cause any interference
Remove all amplifier shielding to ensure maximum cooling
> Running a VHF or UHF power amplifier without shielding presents a safety risk in terms of RF exposure.
A-005-002-011    5-2-11
Harmonics produced in an early stage of a transmitter may be reduced in a later stage by:
tuned circuit coupling between stages
larger value coupling capacitors
greater input to the final stage
transistors instead of tubes
> Key words:  STAGES.  Resonant circuits in the coupling between stages help convey only the operating frequency.  Larger coupling capacitors would pass the harmonics more readily.
A-005-003-001    5-3-1
In a simple 2 stage CW transmitter circuit, the oscillator stage and the class C amplifier stage are inductively coupled by a RF transformer. Another role of the RF transformer is to:
be part of a tuned circuit
act as part of a pi filter
provide the necessary feedback for oscillation
act as part of a balanced mixer
> A simple two-stage CW transmitter comprises an oscillator and a Class-C power amplifier.  A transformer at the output of the oscillator serves the dual purpose of tuned circuit and coupling to the next stage.  The DC supply to the final amplifier is bypassed to ground with a capacitor and decoupled through an RF choke so RF is kept out of the supply.
A-005-003-002    5-3-2
In a simple 2 stage CW transmitter, current to the collector of the transistor in the class C amplifier stage flows through a radio frequency choke (RFC) and a tapped inductor. The RFC, on the tapped inductor side, is also connected to grounded capacitors. The purpose of the RFC and capacitors is to:
form a low-pass filter
provide negative feedback
form a key-click filter
form a RF-tuned circuit
> A simple two-stage CW transmitter comprises an oscillator and a Class-C power amplifier.  A transformer at the output of the oscillator serves the dual purpose of tuned circuit and coupling to the next stage.  The DC supply to the final amplifier is bypassed to ground with a capacitor and decoupled through an RF choke so RF is kept out of the supply.
A-005-003-003    5-3-3
In a simple 2 stage CW transmitter, the transistor in the second stage would act as:
a power amplifier
a frequency multiplier
the master oscillator
an audio oscillator
> A simple two-stage CW transmitter comprises an oscillator and a Class-C power amplifier.  A transformer at the output of the oscillator serves the dual purpose of tuned circuit and coupling to the next stage.  The DC supply to the final amplifier is bypassed to ground with a capacitor and decoupled through an RF choke so RF is kept out of the supply.
A-005-003-004    5-3-4
An advantage of keying the buffer stage in a transmitter is that:
changes in oscillator frequency are less likely
key clicks are eliminated
the radiated bandwidth is restricted
high RF voltages are not present
> Keying a subsequent stage provides the oscillator with a fairly constant load (isolation) and allows it to run continuously for better stability.
A-005-003-005    5-3-5
As a power amplifier is tuned, what reading on its grid current meter indicates the best neutralization?
A minimum change in grid current as the output circuit is changed
Minimum grid current
Maximum grid current
A maximum change in grid current as the output circuit is changed
> Undesired positive feedback in an RF amplifier causes parasitic oscillations:  the amplifier becomes an oscillator.  Inter-electrode capacitance (e.g., plate-to-grid), coupling from output to input, stray inductance or capacitance can start up oscillations.  Neutralization is the process of cancelling positive-feedback paths.  To test a tube amplifier for parasitic oscillations, connect nothing to the input and output terminals, apply DC power, monitor grid and plate current while slowly varying the controls on the output tuning network;  if grid current develops or plate current changes, oscillations are present.
A-005-003-006    5-3-6
What does a neutralizing circuit do in an RF amplifier?
It cancels the effects of positive feedback
It eliminates AC hum from the power supply
It reduces incidental grid modulation
It controls differential gain
> Undesired positive feedback in an RF amplifier causes parasitic oscillations:  the amplifier becomes an oscillator.  Inter-electrode capacitance (e.g., plate-to-grid), coupling from output to input, stray inductance or capacitance can start up oscillations.  Neutralization is the process of cancelling positive-feedback paths.  To test a tube amplifier for parasitic oscillations, connect nothing to the input and output terminals, apply DC power, monitor grid and plate current while slowly varying the controls on the output tuning network;  if grid current develops or plate current changes, oscillations are present.
A-005-003-007    5-3-7
What is the reason for neutralizing the final amplifier stage of a transmitter?
To eliminate parasitic oscillations
To limit the modulation index
To cut off the final amplifier during standby periods
To keep the carrier on frequency
> Undesired positive feedback in an RF amplifier causes parasitic oscillations:  the amplifier becomes an oscillator.  Inter-electrode capacitance (e.g., plate-to-grid), coupling from output to input, stray inductance or capacitance can start up oscillations.  Neutralization is the process of cancelling positive-feedback paths.  To test a tube amplifier for parasitic oscillations, connect nothing to the input and output terminals, apply DC power, monitor grid and plate current while slowly varying the controls on the output tuning network;  if grid current develops or plate current changes, oscillations are present.
A-005-003-008    5-3-8
Parasitic oscillations are usually generated due to:
accidental resonant frequencies in the power amplifier
harmonics from some earlier multiplier stage
excessive drive or excitation to the power amplifier
a mismatch between power amplifier and transmission line
> Undesired positive feedback in an RF amplifier causes parasitic oscillations:  the amplifier becomes an oscillator.  Inter-electrode capacitance (e.g., plate-to-grid), coupling from output to input, stray inductance or capacitance can start up oscillations.  Neutralization is the process of cancelling positive-feedback paths.  To test a tube amplifier for parasitic oscillations, connect nothing to the input and output terminals, apply DC power, monitor grid and plate current while slowly varying the controls on the output tuning network;  if grid current develops or plate current changes, oscillations are present.
A-005-003-009    5-3-9
Parasitic oscillations would tend to occur mostly in:
RF power output stages
high gain audio output stages
high voltage rectifiers
mixer stages
> Undesired positive feedback in an RF amplifier causes parasitic oscillations:  the amplifier becomes an oscillator.  Inter-electrode capacitance (e.g., plate-to-grid), coupling from output to input, stray inductance or capacitance can start up oscillations.  Neutralization is the process of cancelling positive-feedback paths.  To test a tube amplifier for parasitic oscillations, connect nothing to the input and output terminals, apply DC power, monitor grid and plate current while slowly varying the controls on the output tuning network;  if grid current develops or plate current changes, oscillations are present.
A-005-003-010    5-3-10
Why is neutralization necessary for some vacuum-tube amplifiers?
To cancel oscillation caused by the effects of interelectrode capacitance
To reduce grid-to-cathode leakage
To cancel AC hum from the filament transformer
To reduce the limits of loaded Q
> Undesired positive feedback in an RF amplifier causes parasitic oscillations:  the amplifier becomes an oscillator.  Inter-electrode capacitance (e.g., plate-to-grid), coupling from output to input, stray inductance or capacitance can start up oscillations.  Neutralization is the process of cancelling positive-feedback paths.  To test a tube amplifier for parasitic oscillations, connect nothing to the input and output terminals, apply DC power, monitor grid and plate current while slowly varying the controls on the output tuning network;  if grid current develops or plate current changes, oscillations are present.
A-005-003-011    5-3-11
Parasitic oscillations in an RF power amplifier may be caused by:
lack of neutralization
overdriven stages
poor voltage regulation
excessive harmonic production
> Undesired positive feedback in an RF amplifier causes parasitic oscillations:  the amplifier becomes an oscillator.  Inter-electrode capacitance (e.g., plate-to-grid), coupling from output to input, stray inductance or capacitance can start up oscillations.  Neutralization is the process of cancelling positive-feedback paths.  To test a tube amplifier for parasitic oscillations, connect nothing to the input and output terminals, apply DC power, monitor grid and plate current while slowly varying the controls on the output tuning network;  if grid current develops or plate current changes, oscillations are present.
A-005-004-001    5-4-1
What type of signal does a balanced modulator produce?
Double sideband, suppressed carrier
FM with balanced deviation
Full carrier
Single sideband, suppressed carrier
> One method of producing SSB is a Balanced Modulator followed by a filter.  The modulator takes in a fixed-frequency RF signal and mixes it with audio from the speech amplifier.  The modulator is said to be balanced because the two original inputs are not present at the output:  carrier suppression has taken place.  Present, however, are a lower and upper sideband.  A subsequent filter selects one of the sidebands to complete the creation of a single sideband suppressed-carrier signal.  Note that there is no RF output when no audio is applied.
A-005-004-002    5-4-2
How can a single-sideband phone signal be produced?
By using a balanced modulator followed by a filter
By driving a product detector with a DSB signal
By using a loop modulator followed by a mixer
By using a reactance modulator followed by a mixer
> One method of producing SSB is a Balanced Modulator followed by a filter.  The modulator takes in a fixed-frequency RF signal and mixes it with audio from the speech amplifier.  The modulator is said to be balanced because the two original inputs are not present at the output:  carrier suppression has taken place.  Present, however, are a lower and upper sideband.  A subsequent filter selects one of the sidebands to complete the creation of a single sideband suppressed-carrier signal.  Note that there is no RF output when no audio is applied.
A-005-004-003    5-4-3
Carrier suppression in a single-sideband transmitter takes place in:
the balanced modulator stage
the carrier decouple stage
the mechanical filter
the frequency multiplier stage
> One method of producing SSB is a Balanced Modulator followed by a filter.  The modulator takes in a fixed-frequency RF signal and mixes it with audio from the speech amplifier.  The modulator is said to be balanced because the two original inputs are not present at the output:  carrier suppression has taken place.  Present, however, are a lower and upper sideband.  A subsequent filter selects one of the sidebands to complete the creation of a single sideband suppressed-carrier signal.  Note that there is no RF output when no audio is applied.
A-005-004-004    5-4-4
Transmission with SSB, as compared to conventional AM transmission, results in:
6 dB gain in the transmitter and 3 dB gain in the receiver
6 dB gain in the receiver
a greater bandpass requirement in the receiver
3 dB gain in the transmitter
> Under noisy conditions, SSB can bring up to a 9 dB improvement over an AM signal of the same peak power.  In AM, the Peak Envelope Power present in one of the two sidebands equals one fourth the carrier power:  e.g., a 100-watt AM transmitter only packs 25 watts PEP in each sideband.  SSB concentrates all the available power in one sideband alone:  a 4 to 1 improvement or 6 dB.  Using half the bandwidth on SSB reception, permits taking in only half of the noise at the receiver, an additional 3 dB improvement.
A-005-004-005    5-4-5
The peak power output of a single-sideband transmitter, when being tested by a two-tone generator is:
twice the RF power output of any of the tones
equal to the RF peak output power of any of the tones
one-half of the RF peak output power of any of the tones
one-quarter of the RF peak output power of any of the tones
> A two-tone test permits verifying the linearity of an SSB transmitter.  The test requires a generator producing two low-distortion non-harmonically related audio sine waves of equal amplitude.  The frequencies must fall within the normal transmitter audio passband:  e.g., 700 and 1900 Hz.  A sample of the transmitter's output is observed on an oscilloscope while the tones are fed into the microphone input.  Feeding an SSB transmitter with two equal-amplitude steady audio tones produces two equal-amplitude RF signals:  total power is thus twice the power present in each RF signal.
A-005-004-006    5-4-6
What kind of input signal is used to test the amplitude linearity of a single-sideband phone transmitter while viewing the output on an oscilloscope?
Two audio-frequency sine waves
An audio-frequency sine wave
An audio-frequency square wave
Normal speech
> A two-tone test permits verifying the linearity of an SSB transmitter.  The test requires a generator producing two low-distortion non-harmonically related audio sine waves of equal amplitude.  The frequencies must fall within the normal transmitter audio passband:  e.g., 700 and 1900 Hz.  A sample of the transmitter's output is observed on an oscilloscope while the tones are fed into the microphone input.  Feeding an SSB transmitter with two equal-amplitude steady audio tones produces two equal-amplitude RF signals:  total power is thus twice the power present in each RF signal.
A-005-004-007    5-4-7
When testing the amplitude linearity of a single-sideband transmitter what audio tones are fed into the microphone input and on what kind of kind of instrument is the output observed?
Two non-harmonically related tones are fed in, and the output is observed on an oscilloscope
Two harmonically related tones are fed in, and the output is observed on an oscilloscope
Two harmonically related tones are fed in, and the output is observed on a distortion analyzer
Two non-harmonically related tones are fed in, and the output is observed on a distortion analyzer
> A two-tone test permits verifying the linearity of an SSB transmitter.  The test requires a generator producing two low-distortion non-harmonically related audio sine waves of equal amplitude.  The frequencies must fall within the normal transmitter audio passband:  e.g., 700 and 1900 Hz.  A sample of the transmitter's output is observed on an oscilloscope while the tones are fed into the microphone input.  Feeding an SSB transmitter with two equal-amplitude steady audio tones produces two equal-amplitude RF signals:  total power is thus twice the power present in each RF signal.
A-005-004-008    5-4-8
What audio frequencies are used in a two-tone test of the linearity of a single-sideband phone transmitter?
Any two audio tones may be used, but they must be within the transmitter audio passband, and should not be harmonically related
20 Hz and 20 kHz tones must be used
1200 Hz and 2400 Hz tones must be used
Any two audio tones may be used, but they must be within the transmitter audio passband, and must be harmonically related
> A two-tone test permits verifying the linearity of an SSB transmitter.  The test requires a generator producing two low-distortion non-harmonically related audio sine waves of equal amplitude.  The frequencies must fall within the normal transmitter audio passband:  e.g., 700 and 1900 Hz.  A sample of the transmitter's output is observed on an oscilloscope while the tones are fed into the microphone input.  Feeding an SSB transmitter with two equal-amplitude steady audio tones produces two equal-amplitude RF signals:  total power is thus twice the power present in each RF signal.
A-005-004-009    5-4-9
What measurement can be made of a single-sideband phone transmitter's amplifier by performing a two-tone test using an oscilloscope?
Its linearity
Its frequency deviation
Its percent of carrier phase shift
Its percent of frequency modulation
> A two-tone test permits verifying the linearity of an SSB transmitter.  The test requires a generator producing two low-distortion non-harmonically related audio sine waves of equal amplitude.  The frequencies must fall within the normal transmitter audio passband:  e.g., 700 and 1900 Hz.  A sample of the transmitter's output is observed on an oscilloscope while the tones are fed into the microphone input.  Feeding an SSB transmitter with two equal-amplitude steady audio tones produces two equal-amplitude RF signals:  total power is thus twice the power present in each RF signal.
A-005-004-010    5-4-10
How much is the carrier suppressed below peak output power in a single-sideband phone transmission?
At least 40 dB
No more than 20 dB
No more than 30 dB
At least 60 dB
> "Most well-designed balanced modulators can provide between 30 and 50 dB of carrier suppression.  ...The filter roll-off can be used to obtain an additional 20 dB of carrier suppression." (ARRL Handbook 1985)
A-005-004-011    5-4-11
What is meant by "flat topping" in a single-sideband phone transmission?
Signal distortion caused by excessive drive
Signal distortion caused by insufficient collector current
The transmitter's automatic level control is properly adjusted
The transmitter's carrier is properly suppressed
> Flattening of the peaks is an extreme form of distortion where the output of the transmitter is incapable of reproducing the original pattern of the audio input on voice peaks.  This is generally caused by excessive audio input to the transmitter:  too much audio causes the amplifier stage to exceed its linear operation range.  The purpose of the ALC (Automatic Level Control) is to prevent overdrive.

' --  --  --  --

A-005-007-001    5-7-1
Maintaining the peak RF output of a SSB transmitter at a relatively constant level requires a circuit called the:
automatic level control (ALC)
automatic gain control (AGC)
automatic output control (AOC)
automatic volume control (AVC)
> Automatic Level Control (ALC) serves to prevent overdriving an amplifier.  The ALC circuit samples the envelope (peak) of the RF output to develop a DC control voltage used to control the gain of an earlier stage.  AGC and AVC are receiver circuits.
A-005-007-002    5-7-2
Speech compression associated with SSB transmission implies:
full amplification of low level signals and reducing or eliminating amplification of high level signals
full amplification of high level signals and reducing or eliminating signals amplification of low level
a lower signal-to-noise ratio
circuit level instability
> Audio compression maintains a high voice level despite variations in the voice signal incoming from a microphone.  To produce a high average output without exceeding a certain peak value, low level signals need to be amplified while high level signals are passed along with little or no gain.  [ compression is the automatic reduction of gain as the signal level increases beyond a pre-set level known as the threshold. ]
A-005-007-007    5-7-7
Which principle is not associated with analog signal processing?
Frequency division
Compression
Bandwidth limiting
Clipping
> Key words:  NOT ASSOCIATED WITH ANALOG.  Compression, bandwidth limiting and clipping can all be performed as analog processes.  Frequency division requires a numerical computation.
A-005-007-008    5-7-8
Which of the following is not a method used for peak limiting, in a signal processor?
Frequency clipping
RF clipping
Compression
AF clipping
> The expression "peak limiting" entails limiting the amplitude.  Compression, AF clipping and RF clipping are valid operations.  There is no such thing as frequency clipping.
A-005-007-009    5-7-9
What is the undesirable result of AF clipping in a speech processor?
Increased harmonic distortion
Reduced average power
Increased average power
Reduction in peak amplitude
> Audio frequency clipping abruptly stops voltage excursions at a certain level.  This gives the audio a square wave appearance;  square waves are rich in harmonics.  AF clippers need to be followed by a low-pass filter to prevent harmonics from entering modulation stages.  You may also eliminate the bad answers:  "reduction in peak amplitude" is the object of clipping, "increased average power" is a result of clipping (softer passages are no longer dwarfed by the peaks), "increased average power" simply contradicts the previous answer.
A-005-007-010    5-7-10
Which description is not correct? You are planning to build a speech processor for your transceiver. Compared to AF clipping, RF clipping:
is easier to implement
has less distortion
is more expensive to implement
is more difficult to implement
> Working at radio-frequencies is evidently more difficult and thus more expensive than dealing with audio frequencies.  RF clipping is generally presumed to induce less distortion because any harmonics generated through clipping automatically end up outside the passband of subsequent filters.  At audio frequencies, harmonics of the lower speech frequencies fall within the audio passband and can muddle the audio signal.
A-005-007-011    5-7-11
Automatic Level Control (ALC) is another name for:
RF compression
AF compression
RF clipping
AF clipping
> Clipping places a hard limit on voltage swings.  Compression is a reduction in gain when signal exceed a certain threshold.  The ALC circuit samples the envelope (peak) of the RF output and produces a DC control voltage used to control the gain of an earlier stage when the output reaches a certain level.

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A-005-005-001    5-5-1
In an FM phone signal having a maximum frequency deviation of 3000 Hz either side of the carrier frequency, what is the modulation index, when the modulating frequency is 1000 Hz?
3
0.3
3000
1000
> Deviation = the amount of frequency shift, at a given instant, from the centre carrier frequency (e.g., plus or minus 5 kHz).  Modulation Index = the ratio of deviation to modulating frequency for a particular audio frequency (both being expressed in the same units):  e.g., 3 kHz deviation with 1 kHz audio represents a Modulation Index of 3.  Deviation Ratio = the ratio of maximum deviation to the maximum modulating frequency:  e.g. maximum deviation of 5 kHz with a highest modulating frequency of 3 kHz is a Deviation Ratio of 1.66 .
A-005-005-002    5-5-2
What is the modulation index of an FM phone transmitter producing an instantaneous carrier deviation of 6 kHz when modulated with a 2 kHz modulating frequency?
3
0.333
2000
6000
> Deviation = the amount of frequency shift, at a given instant, from the centre carrier frequency (e.g., plus or minus 5 kHz).  Modulation Index = the ratio of deviation to modulating frequency for a particular audio frequency (both being expressed in the same units):  e.g., 3 kHz deviation with 1 kHz audio represents a Modulation Index of 3.  Deviation Ratio = the ratio of maximum deviation to the maximum modulating frequency:  e.g. maximum deviation of 5 kHz with a highest modulating frequency of 3 kHz is a Deviation Ratio of 1.66 .
A-005-005-003    5-5-3
What is the deviation ratio of an FM phone transmitter having a maximum frequency swing of plus or minus 5 kHz and accepting a maximum modulation rate of 3 kHz?
1.66
60
0.16
0.6
> Deviation = the amount of frequency shift, at a given instant, from the centre carrier frequency (e.g., plus or minus 5 kHz).  Modulation Index = the ratio of deviation to modulating frequency for a particular audio frequency (both being expressed in the same units):  e.g., 3 kHz deviation with 1 kHz audio represents a Modulation Index of 3.  Deviation Ratio = the ratio of maximum deviation to the maximum modulating frequency:  e.g. maximum deviation of 5 kHz with a highest modulating frequency of 3 kHz is a Deviation Ratio of 1.66 .
A-005-005-004    5-5-4
What is the deviation ratio of an FM phone transmitter having a maximum frequency swing of plus or minus 7.5 kHz and accepting a maximum modulation rate of 3.5 kHz?
2.14
0.47
47
0.214
> Deviation = the amount of frequency shift, at a given instant, from the centre carrier frequency (e.g., plus or minus 5 kHz).  Modulation Index = the ratio of deviation to modulating frequency for a particular audio frequency (both being expressed in the same units):  e.g., 3 kHz deviation with 1 kHz audio represents a Modulation Index of 3.  Deviation Ratio = the ratio of maximum deviation to the maximum modulating frequency:  e.g. maximum deviation of 5 kHz with a highest modulating frequency of 3 kHz is a Deviation Ratio of 1.66 .
A-005-005-005    5-5-5
When the transmitter is not modulated, or the amplitude of the modulating signal is zero, the frequency of the carrier is called its:
centre frequency
frequency deviation
frequency shift
modulating frequency
> Centre Frequency is the transmitter output frequency in the absence of modulation.  Frequency deviation and frequency shift both are synonyms for the offset in carrier frequency caused by modulation at a given instant.  Modulating frequency relates to the audio frequency used for modulation.
A-005-005-006    5-5-6
In an FM transmitter system, the amount of deviation from the centre frequency is determined solely by the:
amplitude of the modulating frequency
frequency of the modulating frequency
amplitude and the frequency of the modulating frequency
modulating frequency and the amplitude of the centre frequency
> In Frequency Modulation,  the amplitude of the modulation is translated into the importance of the deviation, the modulation frequency is reflected in the rhythm of the deviation.
A-005-005-007    5-5-7
Any FM wave with single-tone modulation has:
an infinite number of sideband frequencies
two sideband frequencies
four sideband frequencies
one sideband frequency
> Unlike AM where a single modulating frequency creates only a pair of side frequencies (one on each side of the carrier), FM creates an infinite number of side frequency pairs;  the Modulation Index influences the amplitude of the side frequencies through a mathematical relation known as a Bessel Function.  The number of side frequencies with significant amplitude determines the required bandwidth.  For certain Modulation Index values, there is zero energy at the centre frequency;  the energy is then totally found in the side frequencies.
A-005-005-008    5-5-8
Some types of deviation meters work on the principle of:
a carrier null and multiplying the modulation frequency by the modulation index
detecting the frequencies in the sidebands
the amplitude of power in the sidebands
a carrier peak and dividing by the modulation index
> Certain Modulation Index values cause nulls at the centre carrier frequency:  e.g., the Bessel function returns zero for the carrier component at Modulation Indices of 2.4048, 5.5201 or 8.6537 .  Detecting a carrier null permits determining deviation as Modulation Index times modulating frequency.  For example, with a tone of 905 hertz and deviation set at 4996 hertz (nearly 5 kHz), a null in the carrier will be observed because 4996 Hz deviation for a tone of 905 Hz is a Modulation Index of 5.52 .  An all-mode receiver with a sharp filter permits observing the carrier component.  The procedure could be used to set a transmitter or calibrate a home-made deviation meter.
' Expressed to 8 decimal places, the first three indices producing Bessel nulls for J(0) are 2.40482556, 5.52007811 and 8.65372791.
A-005-005-009    5-5-9
When using some deviation meters, it is important to know:
modulating frequency and the modulation index
modulation index
modulating frequency
pass-band of the IF filter
> Certain Modulation Index values cause nulls at the centre carrier frequency:  e.g., the Bessel function returns zero for the carrier component at Modulation Indices of 2.4048, 5.5201 or 8.6537 .  Detecting a carrier null permits determining deviation as Modulation Index times modulating frequency.  For example, with a tone of 905 hertz and deviation set at 4996 hertz (nearly 5 kHz), a null in the carrier will be observed because 4996 Hz deviation for a tone of 905 Hz is a Modulation Index of 5.52 .  An all-mode receiver with a sharp filter permits observing the carrier component.  The procedure could be used to set a transmitter or calibrate a home-made deviation meter.
A-005-005-010    5-5-10
What is the significant bandwidth of an FM-phone transmission having a +/- 5-kHz deviation and a 3-kHz modulating frequency?
16 kHz
8 kHz
5 kHz
3 kHz
> Carson's Rule permits estimating the bandwidth of an FM signal:  bandwidth equals twice the sum of deviation + modulating frequency, in this example,  5 + 3 = 8, twice 8 = 16.  [ Mathematician and engineer John R. Carson (1887-1940) had predicted the approximate bandwidth of an FM signal circa 1922. ]
A-005-005-011    5-5-11
What is the frequency deviation for a 12.21-MHz reactance-modulated oscillator in a +/- 5-kHz deviation, 146.52-MHz FM-phone transmitter?
+/- 416.7 Hz
+/- 12 kHz
+/- 5 kHz
+/- 41.67 Hz
> In this example, the frequency multiplication ratio between oscillator and output is 12 ( 146.52 divided by 12.21 = 12 ).  Hence, the oscillator needs only be shifted by 416.7 Hz, i.e., 5000 Hz divided by 12.

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A-005-006-005    5-6-5
What type of circuit varies the tuning of an amplifier tank circuit to produce FM signals?
A phase modulator
A balanced modulator
A double balanced mixer
An audio modulator
> Two methods exist to produce Frequency Modulation.  The Direct Method supposes forcing deviation directly on the oscillator;  deviation is then multiplied along with the oscillator frequency up to the operating frequency.  Phase Modulation is an indirect method whereby the phase of the signal is affected (i.e., retarding/advancing) in step with the modulation by varying a reactance on a stage other than the oscillator.
A-005-006-006    5-6-6
What audio shaping network is added at an FM transmitter to attenuate the lower audio frequencies?
A pre-emphasis network
An audio prescaler
A heterodyne suppressor
A de-emphasis network
> With direct FM, deviation is independent of modulating frequency, actual deviation is determined solely by the modulating amplitude.  With Phase Modulation, deviation depends on the amount of phase shift and its rapidity, increasing modulating frequency results in proportionally more deviation even if amplitude is held constant.  Because commercial standards were based on Phase Modulation, an FM transmitter requires an artificial boost in high frequency response so that PM and FM sound the same at the receiver.  A pre-emphasis network tailors the frequency response in the FM transmitter.  De-emphasis is employed in the receiver to restore a flat audio response.
A-005-006-008    5-6-8
The characteristic difference between a phase modulator and a frequency modulator is:
pre-emphasis
the centre frequency
de-emphasis
frequency inversion
> With direct FM, deviation is independent of modulating frequency, actual deviation is determined solely by the modulating amplitude.  With Phase Modulation, deviation depends on the amount of phase shift and its rapidity, increasing modulating frequency results in proportionally more deviation even if amplitude is held constant.  Because commercial standards were based on Phase Modulation, an FM transmitter requires an artificial boost in high frequency response so that PM and FM sound the same at the receiver.  A pre-emphasis network tailors the frequency response in the FM transmitter.  De-emphasis is employed in the receiver to restore a flat audio response.
A-005-006-009    5-6-9
In most modern FM transmitters, to produce a better sound, a compressor and a clipper are placed:
between the audio amplifier and the modulator
between the multiplier and the PA
between the modulator and the oscillator
in the microphone circuit, before the audio amplifier
> In this context, compression and clipping are AUDIO processes aimed at maintaining high average deviation without exceeding a given peak value.  Two answers can be readily scratched as they pertain to radiofrequency (RF) paths.  The microphone circuit is not suitable as the audio level at that point is too low for a simple clipper.
A-005-006-010    5-6-10
Three important parameters to be verified in an FM transmitter are:
power, frequency deviation and frequency stability
distortion, bandwidth and sideband power
modulation, pre-emphasis and carrier suppression
frequency stability, de-emphasis and linearity
> Stability is paramount in all transmitters, frequency deviation ultimately determines bandwidth while linearity (absence of distortion) minimizes out-of-channel emissions.  Carrier Suppression is a concern with SSB, pre-emphasis (FM transmitter) and de-emphasis (FM receiver) are simple resistor-capacitor networks.

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{L16} FM Repeaters.

A-005-006-001    5-6-1
If the signals of two repeater transmitters mix together in one or both of their final amplifiers and unwanted signals at the sum and difference frequencies of the original signals are generated and radiated, what is this called?
Intermodulation interference
Neutralization
Adjacent channel interference
Amplifier desensitization
> Intermodulation is the unwanted mixing of two or more signals that produce new signals (products).  The fundamental or harmonic energy from strong nearby transmitters intermix to create intermodulation products.  Mixing can take place in the front-end of the affected receiver, in the Power Amplifier of one of the transmitters or through "external rectification or passive intermodulation" (in some electronic device or some corroded junction between two metals acting as a diode mixer).
A-005-006-002    5-6-2
How does intermodulation interference between two repeater transmitters usually occur?
When they are in close proximity and the signals mix in one or both of their final amplifiers
When the signals are reflected in phase by aircraft passing overhead
When they are in close proximity and the signals cause feedback in one or both of their final amplifiers
When the signals are reflected out of phase by aircraft passing overhead
> Intermodulation is the unwanted mixing of two or more signals that produce new signals (products).  The fundamental or harmonic energy from strong nearby transmitters intermix to create intermodulation products.  Mixing can take place in the front-end of the affected receiver, in the Power Amplifier of one of the transmitters or through "external rectification or passive intermodulation" (in some electronic device or some corroded junction between two metals acting as a diode mixer).
A-005-006-003    5-6-3
How can intermodulation interference between two repeater transmitters in close proximity often be reduced or eliminated?
By installing a terminated circulator or ferrite isolator in the transmission line to the transmitter and duplexer
By installing a low-pass filter in the antenna transmission line
By installing a high-pass filter in the antenna transmission line
By using a Class C final amplifier with high driving power
> A circulator is usually a three-port device;  any energy coming in one port is forwarded in one direction only, towards the next port.  An isolator is a circulator with one port terminated into a dummy load.  With the transmitter on port 1, the antenna on port 2 and a dummy load on port 3, RF from the transmitter is routed to the antenna but any outside energy picked-up by the antenna is diverted to the dummy load and thus cannot enter the Power Amplifier where it might lead to intermodulation.  Magnetized ferrite material is used in the fabrication of circulators.
A-005-006-004    5-6-4
If a receiver tuned to 146.70 MHz receives an intermodulation product signal whenever a nearby transmitter transmits on 146.52, what are the two most likely frequencies for the other interfering signal?
146.34 MHz and 146.61 MHz
146.88 MHz and 146.34 MHz
146.01 MHz and 147.30 MHz
73.35 MHz and 239.40 MHz
> Third Order Intermodulation products where the second harmonic of one signal mixes with the fundamental frequency of another are the most troublesome because of the relative frequency proximity of the involved signals:  filtering them out is difficult.  Given two signals, F1 and F2, the Third Order IMD product can be computed as (a) "twice F1 minus F2" or (b) "twice F2 minus F1".  In this example, IMD = 146.70, F1 = 146.52 ; solving for F2 in case "a" is (F1 times 2), minus IMD ;  solving for F2 in case "b" is (IMD + F1), divided by 2.
A-005-006-007    5-6-7
Which type of filter would be best to use in a 2-metre repeater duplexer?
A cavity filter
A DSP filter
An L-C filter
A crystal filter
> In the context of a repeater installation, a duplexer is a specialized filter which allows operating the receiver and transmitter simultaneously on the same antenna.  The duplexer is built with four or more quarter-wavelength cavity resonators.  The duplexer provides isolation ( 90 dB or more on 2 m ) between the receive and transmit paths at the expense of insertion loss.
A-005-006-011    5-6-11
Intermodulation interference products are not typically associated with which of the following:
intermediate frequency stage
final amplifier stage
receiver frontend
passive intermodulation
> "Undesired mixing of two or more frequencies in a non-linear device which produces additional sum and difference frequencies" (ARRL RFI Book).  Final amplifier stage: signals from nearby transmitters may find their way into a power amplifier creating intermodulation.  Receiver front-end: strong offending signals may enter the RF amplifier or mixer and create intermodulation.  Passive intermodulation (PIM), sometimes called "rusty bolt effect": passive devices subjected to strong signals cause the problem; cables, antennas, connectors, dissimilar metals, etc. due to oxidation, corrosion, metal flakes, dirty mating surfaces or poor contact.

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{L10} Digital Transmission Techniques.

A-005-008-001    5-8-1
What digital code consists of elements having unequal length?
Varicode
AX.25
Baudot
ASCII
> Varicode is an encoding method where ASCII characters are represented by bit patterns ranging from 1 to 10 bits in length.  Varicode is used for PSK31 ("Phase Shift Keying, 31 Baud").  ASCII (American Standard Code for Information Interchange) or Baudot (RTTY) rely on a precise number of evenly-timed bits.  AX.25 is a protocol used for packet transmission.
A-005-008-002    5-8-2
Open Systems Interconnection (OSI) model standardizes communications functions as layers within a data communications system.  Amateur digital radio systems often follow the OSI model in structure. What is the base layer of the OSI model involving the interconnection of a packet radio TNC to a computer terminal?
The physical layer
The link layer
The network layer
The transport layer
> Key words:  TNC to COMPUTER INTERCONNECTION.  Physical layer (for example, RS-232):  the electrical, mechanical, procedural and functional specifications for moving data across a physical medium, including modulation, establishing and terminating connections.  The Data Link layer packages data bits into frames, provides error-free transfer of frames including physical addressing, network topology, error notification.  The Network layer (for example, Internetwork Protocol) uses logical addresses to route frames through a network of links.  The Transport layer (for example, TCP Transmission Control Protocol) provides the end-to-end control, ensures that data is complete and properly sequenced ( e.g., retransmissions ).
A-005-008-003    5-8-3
What is the purpose of a Cyclic Redundancy Check (CRC)?
Error detection
Lossy compression
Error correction
Lossless compression
> "A cyclic redundancy check (CRC) is an error-detecting code commonly used in digital networks and storage devices to detect accidental changes to raw data" (Wikipedia).  A CRC is computed at the originating end and sent with the message; the receiving end does the same calculation, a mismatch in the CRC indicates that the payload was damaged.  The CRC manages error detection, other mechanisms can provide error correction.
A-005-008-004    5-8-4
What is one advantage of using ASCII rather than Baudot code?
It includes both upper and lower case text characters in the code
ASCII includes built-in error correction
ASCII characters contain fewer information bits
The larger character set allows store-and-forward
> With 5 bits, Baudot can accommodate 32 combinations ( 2 exponent 5 ) per character set;  one set represents uppercase letters A through Z, the other are figures 0 through 9 plus other symbols.  The original ASCII (American Standard Code for Information Interchange) used seven bits to accommodate 128 combinations;  enough for lowercase and uppercase letters, all digits and other symbols.  So called "extended ASCII" uses 8 bits for a total of 256 combinations, this adds accented letters.
A-005-008-005    5-8-5
What type of error control system is used in AMTOR ARQ (Mode A)?
The receiving station automatically requests repeats when needed
The receiving station checks the frame check sequence (FCS) against the transmitted FCS
Each character is sent twice
Mode A AMTOR does not include an error control system
> AMTOR is similar to RTTY but with error correction added;  a special 7-bit code is used.  Amateur Teleprinting Over Radio (AMTOR) can run under two modes.  Mode B ( FEC - Forward Error Correction ):  characters are sent twice in groups of five in consecutive blocks.  Mode A ( ARQ - Automatic Repeat reQuest ):  characters are transmitted in blocks of 3, receiving station returns a positive acknowledgement or a request to resend.  [ Frame Check Sequence is part of the AX.25 Packet protocol, no relation to AMTOR ]
A-005-008-006    5-8-6
What error-correction system is used in AMTOR FEC (Mode B)?
Each character is sent twice
Mode B AMTOR does not include an error-correction system
The receiving station automatically requests repeats when needed
The receiving station checks the frame check sequence (FCS) against the transmitted FCS
> AMTOR is similar to RTTY but with error correction added;  a special 7-bit code is used.  Amateur Teleprinting Over Radio (AMTOR) can run under two modes.  Mode B ( FEC - Forward Error Correction ):  characters are sent twice in groups of five in consecutive blocks.  Mode A ( ARQ - Automatic Repeat reQuest ):  characters are transmitted in blocks of 3, receiving station returns a positive acknowledgement or a request to resend.  [ Frame Check Sequence is part of the AX.25 Packet protocol, no relation to AMTOR ]
A-005-008-007    5-8-7
APRS (Automatic Packet Reporting System) does NOT support which one of these functions?
Automatic link establishment
Two-way messaging
Telemetry
Amateur-specific local information broadcast
> Key word:  NOT.  "APRS is a digital communications information channel for Ham radio. (...) As a single national channel (...), it gives the mobile ham a place to monitor for 10 to 30 minutes in any area, at any time to capture what is happening in ham radio in the surrounding area.  Announcements, Bulletins, Messages, Alerts, Weather, and of course a map of all this activity including objects, satellites, nets, meetings, hamfests, etc. (...)  APRS also supports global call sign-to-call sign messaging (...)" (www.aprs.org Bob Bruninga WB4APR).  Automatic Link Establishment (ALE) is a standard for systems capable of automatically selecting a band and frequency from a list of channels for HF communications with a given similarly-equipped station.
A-005-008-008    5-8-8
Which algorithm may be used to create a Cyclic Redundancy Check (CRC)?
Hash function
Dynamic Huffman code
Convolution code
Lempel-Ziv routine
> "A hash function is any algorithm that maps data of arbitrary length to data of a fixed length. (...)  The values returned by a hash function are called hash values, hash codes, hash sums, checksums or simply hashes" (Wikipedia).  A convolutional code is a type of error-correcting code (e.g., Viterbi or Reed-Solomon).  Lempel-Ziv and Dynamic Huffman coding are lossless data compression algorithms.
A-005-008-009    5-8-9
The designator AX.25 is associated with which amateur radio mode?
packet
RTTY
ASCII
spread spectrum speech
> Packet radio adheres to the AX.25 protocol.  AX.25 is derived from the X.25 networking protocol:  one notable difference is the use of call signs as addresses.  AX.25 uses a Frame-Check Sequence for error detection.  The Frame-Check sequence (FCS) is a sixteen-bit number calculated by both the sending and receiving stations of a frame.  Comparing the received FCS with a locally computed one permits detecting corruption in transit.
A-005-008-010    5-8-10
How many information bits are included in the Baudot code?
5
7
8
6
> With 5 bits, Baudot can accommodate 32 combinations ( 2 exponent 5 ) per character set;  one set represents uppercase letters A through Z, the other are figures 0 through 9 plus other symbols.  The original ASCII (American Standard Code for Information Interchange) used seven bits to accommodate 128 combinations;  enough for lowercase and uppercase letters, all digits and other symbols.  So called "extended ASCII" uses 8 bits for a total of 256 combinations, this adds accented letters.
A-005-008-011    5-8-11
How many information bits are included in the ISO-8859 extension to the ASCII code?
8
7
6
5
> With 5 bits, Baudot can accommodate 32 combinations ( 2 exponent 5 ) per character set;  one set represents uppercase letters A through Z, the other are figures 0 through 9 plus other symbols.  The original ASCII (American Standard Code for Information Interchange) used seven bits to accommodate 128 combinations;  enough for lowercase and uppercase letters, all digits and other symbols.  So called "extended ASCII" uses 8 bits for a total of 256 combinations, this adds accented letters.
A-005-009-001    5-9-1
What term describes a wide-band communications system in which the RF carrier varies according to some predetermined sequence?
Spread spectrum communication
Amplitude-companded single sideband
AMTOR
Time domain frequency modulation
> Spread-spectrum transmission relies on a wide range of frequencies rather than a single one to reduce the effects of noise and interference.  It requires several megahertz of bandwidth.  Frequency-Hopping Spread-Spectrum changes the carrier frequency a number of times per second in a given pattern.  Direct-Sequence Spread-Spectrum uses a pseudo-random bit pattern, many times faster than the data stream, to impress Phase Shift Keying on a carrier.  For proper demodulation, the receiver must synchronize itself with the incoming stream.  Noise and interference do not follow the same pre-agreed patterns and are thus effectively ignored.
A-005-009-002    5-9-2
What is the term used to describe a spread spectrum communications system where the centre frequency of a conventional carrier is changed many times per second in accordance with a pseudorandom list of channels?
Frequency hopping
Direct sequence
Time-domain frequency modulation
Frequency companded spread spectrum
> Spread-spectrum transmission relies on a wide range of frequencies rather than a single one to reduce the effects of noise and interference.  It requires several megahertz of bandwidth.  Frequency-Hopping Spread-Spectrum changes the carrier frequency a number of times per second in a given pattern.  Direct-Sequence Spread-Spectrum uses a pseudo-random bit pattern, many times faster than the data stream, to impress Phase Shift Keying on a carrier.  For proper demodulation, the receiver must synchronize itself with the incoming stream.  Noise and interference do not follow the same pre-agreed patterns and are thus effectively ignored.
A-005-009-003    5-9-3
What term is used to describe a spread spectrum communications system in which a very fast binary bit stream is used to shift the phase of an RF carrier?
Direct sequence
Frequency hopping
Phase companded spread spectrum
Binary phase-shift keying
> Spread-spectrum transmission relies on a wide range of frequencies rather than a single one to reduce the effects of noise and interference.  It requires several megahertz of bandwidth.  Frequency-Hopping Spread-Spectrum changes the carrier frequency a number of times per second in a given pattern.  Direct-Sequence Spread-Spectrum uses a pseudo-random bit pattern, many times faster than the data stream, to impress Phase Shift Keying on a carrier.  For proper demodulation, the receiver must synchronize itself with the incoming stream.  Noise and interference do not follow the same pre-agreed patterns and are thus effectively ignored.
A-005-009-004    5-9-4
Frequency hopping is used with which type of transmission?
Spread spectrum
AMTOR
Packet
RTTY
> Spread-spectrum transmission relies on a wide range of frequencies rather than a single one to reduce the effects of noise and interference.  It requires several megahertz of bandwidth.  Frequency-Hopping Spread-Spectrum changes the carrier frequency a number of times per second in a given pattern.  Direct-Sequence Spread-Spectrum uses a pseudo-random bit pattern, many times faster than the data stream, to impress Phase Shift Keying on a carrier.  For proper demodulation, the receiver must synchronize itself with the incoming stream.  Noise and interference do not follow the same pre-agreed patterns and are thus effectively ignored.
A-005-009-005    5-9-5
Direct sequence is used with which type of transmission?
Spread spectrum
AMTOR
Packet
RTTY
> Spread-spectrum transmission relies on a wide range of frequencies rather than a single one to reduce the effects of noise and interference.  It requires several megahertz of bandwidth.  Frequency-Hopping Spread-Spectrum changes the carrier frequency a number of times per second in a given pattern.  Direct-Sequence Spread-Spectrum uses a pseudo-random bit pattern, many times faster than the data stream, to impress Phase Shift Keying on a carrier.  For proper demodulation, the receiver must synchronize itself with the incoming stream.  Noise and interference do not follow the same pre-agreed patterns and are thus effectively ignored.
A-005-009-006    5-9-6
Which type of signal is used to produce a predetermined alteration in the carrier for spread spectrum communication?
Pseudo-random sequence
Frequency-companded sequence
Quantizing noise
Random noise sequence
> Spread-spectrum transmission relies on a wide range of frequencies rather than a single one to reduce the effects of noise and interference.  It requires several megahertz of bandwidth.  Frequency-Hopping Spread-Spectrum changes the carrier frequency a number of times per second in a given pattern.  Direct-Sequence Spread-Spectrum uses a pseudo-random bit pattern, many times faster than the data stream, to impress Phase Shift Keying on a carrier.  For proper demodulation, the receiver must synchronize itself with the incoming stream.  Noise and interference do not follow the same pre-agreed patterns and are thus effectively ignored.
A-005-009-007    5-9-7
Why is it difficult to monitor a spread spectrum transmission?
Your receiver must be frequency-synchronized to the transmitter
It requires narrower bandwidth than most receivers have
It varies too quickly in amplitude
The signal is too distorted for comfortable listening
> Spread-spectrum transmission relies on a wide range of frequencies rather than a single one to reduce the effects of noise and interference.  It requires several megahertz of bandwidth.  Frequency-Hopping Spread-Spectrum changes the carrier frequency a number of times per second in a given pattern.  Direct-Sequence Spread-Spectrum uses a pseudo-random bit pattern, many times faster than the data stream, to impress Phase Shift Keying on a carrier.  For proper demodulation, the receiver must synchronize itself with the incoming stream.  Noise and interference do not follow the same pre-agreed patterns and are thus effectively ignored.
A-005-009-008    5-9-8
What is frequency hopping spread spectrum?
The carrier frequency is changed in accordance with a pseudo-random list of channels
The carrier is amplitude-modulated over a wide range called the spread
The carrier is frequency-companded
The carrier is phase-shifted by a fast binary bit stream
> Spread-spectrum transmission relies on a wide range of frequencies rather than a single one to reduce the effects of noise and interference.  It requires several megahertz of bandwidth.  Frequency-Hopping Spread-Spectrum changes the carrier frequency a number of times per second in a given pattern.  Direct-Sequence Spread-Spectrum uses a pseudo-random bit pattern, many times faster than the data stream, to impress Phase Shift Keying on a carrier.  For proper demodulation, the receiver must synchronize itself with the incoming stream.  Noise and interference do not follow the same pre-agreed patterns and are thus effectively ignored.
A-005-009-009    5-9-9
What is direct-sequence spread spectrum?
The carrier is phase-shifted by a fast binary bit stream
The carrier is amplitude modulated over a range called the spread
The carrier is frequency-companded
The carrier is altered in accordance with a pseudo-random list of channels
> Spread-spectrum transmission relies on a wide range of frequencies rather than a single one to reduce the effects of noise and interference.  It requires several megahertz of bandwidth.  Frequency-Hopping Spread-Spectrum changes the carrier frequency a number of times per second in a given pattern.  Direct-Sequence Spread-Spectrum uses a pseudo-random bit pattern, many times faster than the data stream, to impress Phase Shift Keying on a carrier.  For proper demodulation, the receiver must synchronize itself with the incoming stream.  Noise and interference do not follow the same pre-agreed patterns and are thus effectively ignored.
A-005-009-010    5-9-10
Why are received spread-spectrum signals so resistant to interference?
Signals not using the spectrum-spreading algorithm are suppressed in the receiver
The receiver is always equipped with a special digital signal processor (DSP) interference filter
If interference is detected by the receiver, it will signal the transmitter to change frequencies
The high power used by a spread-spectrum transmitter keeps its signal from being easily overpowered
> Spread-spectrum transmission relies on a wide range of frequencies rather than a single one to reduce the effects of noise and interference.  It requires several megahertz of bandwidth.  Frequency-Hopping Spread-Spectrum changes the carrier frequency a number of times per second in a given pattern.  Direct-Sequence Spread-Spectrum uses a pseudo-random bit pattern, many times faster than the data stream, to impress Phase Shift Keying on a carrier.  For proper demodulation, the receiver must synchronize itself with the incoming stream.  Noise and interference do not follow the same pre-agreed patterns and are thus effectively ignored.
A-005-009-011    5-9-11
How does the spread-spectrum technique of frequency hopping work?
The frequency of an RF carrier is changed very rapidly according to a particular pseudo-random sequence
If interference is detected by the receiver, it will signal the transmitter to change frequency
If interference is detected by the receiver, it will signal the transmitter to wait until the frequency is clear
A pseudo-random bit stream is used to shift the phase of an RF carrier very rapidly in a particular sequence
> Spread-spectrum transmission relies on a wide range of frequencies rather than a single one to reduce the effects of noise and interference.  It requires several megahertz of bandwidth.  Frequency-Hopping Spread-Spectrum changes the carrier frequency a number of times per second in a given pattern.  Direct-Sequence Spread-Spectrum uses a pseudo-random bit pattern, many times faster than the data stream, to impress Phase Shift Keying on a carrier.  For proper demodulation, the receiver must synchronize itself with the incoming stream.  Noise and interference do not follow the same pre-agreed patterns and are thus effectively ignored.

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{L08} Receivers.

A-006-001-001    6-1-1
What are the advantages of the frequency conversion process in a superheterodyne receiver?
Increased selectivity and optimal tuned circuit design
Automatic detection in the RF amplifier and increased sensitivity
Automatic soft-limiting and automatic squelching
Automatic squelching and increased sensitivity
> Down-converting the operating frequency to a lower Intermediate Frequency facilitates selectivity:  for example, 0.6% of 455 kilohertz is 2.7 kHz, 0.6% of 3.7 megahertz is 22 kHz.
A-006-001-002    6-1-2
What factors should be considered when selecting an intermediate frequency?
Image rejection and responses to unwanted signals
Noise figure and distortion
Interference to other services
Cross-modulation distortion and interference
> Two frequencies, one above and one below the Local Oscillator frequency, can produce a mixing result at the Intermediate Frequency.  The one resulting in the unwanted product is the Image Frequency.  With a low Intermediate Frequency, selectivity and gain are easier to achieve but image rejection suffers.  With a high Intermediate Frequency, image rejection is facilitated but selectivity is more difficult to achieve.  A Double-conversion receiver deals with image rejection with an initial conversion and restores selectivity with a subsequent down-conversion.  Two conversions, however, expose the designer to twice the risk of spurious responses due to spurious oscillations in local oscillators.
A-006-001-003    6-1-3
One of the greatest advantages of the double-conversion over the single-conversion receiver is that it:
greater reduction of image interference for a given front end selectivity
is much more stable
is much more sensitive
produces a louder signal at the output
> Two frequencies, one above and one below the Local Oscillator frequency, can produce a mixing result at the Intermediate Frequency.  The one resulting in the unwanted product is the Image Frequency.  With a low Intermediate Frequency, selectivity and gain are easier to achieve but image rejection suffers.  With a high Intermediate Frequency, image rejection is facilitated but selectivity is more difficult to achieve.  A Double-conversion receiver deals with image rejection with an initial conversion and restores selectivity with a subsequent down-conversion.  Two conversions, however, expose the designer to twice the risk of spurious responses due to spurious oscillations in local oscillators.
A-006-001-004    6-1-4
In a communications receiver, a crystal filter would be located in the:
IF circuits
local oscillator
audio output stage
detector
> The Intermediate Frequency chain is responsible for most of the selectivity.  Crystal filters or mechanical filters can be used at the Intermediate Frequency.  Digital Signal Processing (DSP) is used in modern receivers.
A-006-001-005    6-1-5
A multiple conversion superheterodyne receiver is more susceptible to spurious responses than a single-conversion receiver because of the:
additional oscillators and mixing frequencies involved in the design
poorer selectivity in the IF caused by the multitude of frequency changes
greater sensitivity introducing higher levels of RF to the receiver
AGC being forced to work harder causing the stages concerned to overload
> Two frequencies, one above and one below the Local Oscillator frequency, can produce a mixing result at the Intermediate Frequency.  The one resulting in the unwanted product is the Image Frequency.  With a low Intermediate Frequency, selectivity and gain are easier to achieve but image rejection suffers.  With a high Intermediate Frequency, image rejection is facilitated but selectivity is more difficult to achieve.  A Double-conversion receiver deals with image rejection with an initial conversion and restores selectivity with a subsequent down-conversion.  Two conversions, however, expose the designer to twice the risk of spurious responses due to spurious oscillations in local oscillators.
A-006-001-006    6-1-6
In a dual-conversion superheterodyne receiver what are the respective aims of the first and second conversion:
image rejection and selectivity
selectivity and image rejection
selectivity and dynamic range
image rejection and noise figure
> The first conversion to a high IF places the image frequency far away from the operating frequency so it can be optimally rejected by the front-end filtering.  The second conversion to a low IF performs the traditional function of ensuring selectivity to protect the receiver from adjacent channels.
A-006-001-007    6-1-7
Which stage of a receiver has its input and output circuits tuned to the received frequency?
The RF amplifier
The local oscillator
The audio frequency amplifier
The detector
> Key word:  TUNED.  Of all the stages listed, only one runs at the operating frequency:  the radio-frequency amplifier.
A-006-001-008    6-1-8
Which stage of a superheterodyne receiver lies between a tuneable stage and a fixed tuned stage?
Mixer
Radio frequency amplifier
Intermediate frequency amplifier
Local oscillator
> The superheterodyne concept is based on converting the operating frequency to a fixed Intermediate Frequency:  the Mixer performs that function by combining the output of the tuneable RF amplifier with the Local Oscillator signal to feed the fixed-tuned Intermediate Frequency chain.
A-006-001-009    6-1-9
A single conversion receiver with a 9 MHz IF has a local oscillator operating at 16 MHz. The frequency it is tuned to is:
7 MHz
16 MHz
21 MHz
9 MHz
> In a superheterodyne receiver, injection from the Local Oscillator can be above or below the operating frequency.  There could be two answers:  Local Oscillator minus Intermediate Frequency or Local Oscillator plus Intermediate Frequency.
A-006-001-010    6-1-10
A double conversion receiver designed for SSB reception has a beat frequency oscillator and:
two IF stages and two local oscillators
one IF stage and one local oscillator
two IF stages and three local oscillators
two IF stages and one local oscillator
> Key words:  DOUBLE CONVERSION.  Double conversion entails two Mixers, two Local Oscillators and two Intermediate Frequency chains.
A-006-001-011    6-1-11
The advantage of a double conversion receiver over a single conversion receiver is that it:
suffers less from image interference for a given front end sensitivity
does not drift off frequency
is a more sensitive receiver
produces a louder audio signal
> Two frequencies, one above and one below the Local Oscillator frequency, can produce a mixing result at the Intermediate Frequency.  The one resulting in the unwanted product is the Image Frequency.  With a low Intermediate Frequency, selectivity and gain are easier to achieve but image rejection suffers.  With a high Intermediate Frequency, image rejection is facilitated but selectivity is more difficult to achieve.  A Double-conversion receiver deals with image rejection with an initial conversion and restores selectivity with a subsequent down-conversion.  Two conversions, however, expose the designer to twice the risk of spurious responses due to spurious oscillations in local oscillators.
A-006-002-001    6-2-1
The mixer stage of a superheterodyne receiver is used to:
change the frequency of the incoming signal to that of the IF
allow a number of IF frequencies to be used
remove image signals from the receiver
produce an audio frequency for the speaker
> The superheterodyne concept is based on converting the operating frequency to a fixed Intermediate Frequency:  the Mixer performs that function by combining the output of the tuneable RF amplifier with the Local Oscillator signal to feed the fixed-tuned Intermediate Frequency chain.
A-006-002-002    6-2-2
A superheterodyne receiver designed for SSB reception must have a beat-frequency oscillator (BFO) because:
the suppressed carrier must be replaced for detection
it phases out the unwanted sideband signal
it reduces the pass-band of the IF stages
it beats with the receiver carrier to produce the missing sideband
> The Beat Frequency Oscillator feeds the Product Detector for CW and SSB detection.  Mixing the Intermediate Frequency with the BFO signal in the Product Detector produces an audio output.  In Single Sideband, it is said to "reinsert the carrier" as it recreates a reference at the exact frequency at which the carrier, suppressed at the transmitter, would have appeared out of the Intermediate Frequency chain.
A-006-002-003    6-2-3
The first mixer in the receiver mixes the incoming signal with the local oscillator to produce:
an intermediate frequency
an audio frequency
a radio frequency
a high frequency oscillator (HFO) frequency
> The superheterodyne concept is based on converting the operating frequency to a fixed Intermediate Frequency:  the Mixer performs that function by combining the output of the tuneable RF amplifier with the Local Oscillator signal to feed the fixed-tuned Intermediate Frequency chain.
A-006-002-004    6-2-4
If the incoming signal to the mixer is 3 600 kHz and the first IF is 9 MHz, at which one of the following frequencies would the local oscillator (LO) operate?
5 400 kHz
3 400 kHz
10 600 kHz
21 600 kHz
> In a superheterodyne receiver, injection from the Local Oscillator can be above or below the operating frequency.  There could be two answers:  Intermediate Frequency plus operating frequency or Intermediate Frequency minus operating frequency.
A-006-002-005    6-2-5
The BFO is off-set slightly (500 - 1 500 Hz) from the incoming signal to the detector. This is required:
to beat with the incoming signal
to pass the signal without interruption
to provide additional amplification
to protect the incoming signal from interference
> The Beat Frequency Oscillator feeds the Product Detector for CW and SSB detection.  Mixing the Intermediate Frequency with the BFO signal in the Product Detector produces an audio output.  In Single Sideband, it is said to "reinsert the carrier" as it recreates a reference at the exact frequency at which the carrier, suppressed at the transmitter, would have appeared out of the Intermediate Frequency chain.
A-006-002-006    6-2-6
It is very important that the oscillators contained in a superheterodyne receiver are:
stable and spectrally pure
sensitive and selective
stable and sensitive
selective and spectrally pure
> Oscillators need to be free of drift regardless of voltage and temperature variations or mechanical vibrations.  Spectral purity is the absence of harmonics, other spurious oscillations or noise;  purity limits spurious responses in the subsequent mixing processes.
A-006-002-007    6-2-7
In a superheterodyne receiver, a stage before the IF amplifier has a variable capacitor in parallel with a trimmer capacitor and an inductance. The variable capacitor is for:
tuning of the local oscillator (LO)
tuning both the antenna and the BFO
tuning of the beat-frequency oscillator (BFO)
tuning both the antenna and the LO
> Two stages may require tuning ahead of the Intermediate Frequency amplifier:  the preselector and the high-frequency oscillator, commonly known as the Local Oscillator.  As the question alludes to one trimmer and one inductance, only one circuit can be tuned.
A-006-002-008    6-2-8
In a superheterodyne receiver without an RF amplifier, the input to the mixer stage has a variable capacitor in parallel with an inductance. The variable capacitor is for:
tuning the receiver preselector to the reception frequency
tuning both the antenna and the beat-frequency oscillator
tuning the beat-frequency oscillator
tuning both the antenna and the local oscillator
> In the absence of a radio-frequency amplifier, the input to the Mixer must be an antenna tuning circuit.
A-006-002-009    6-2-9
What receiver stage combines a 14.25-MHz input signal with a 13.795-MHz oscillator signal to produce a 455-kHz intermediate frequency (IF) signal?
Mixer
BFO
VFO
Multiplier
> The superheterodyne concept is based on converting the operating frequency to a fixed Intermediate Frequency:  the Mixer performs that function by combining the output of the tuneable RF amplifier with the Local Oscillator signal to feed the fixed-tuned Intermediate Frequency chain.
A-006-002-010    6-2-10
Which two stages in a superheterodyne receiver have input tuned circuits tuned to the same frequency?
RF and first mixer
IF and local oscillator
RF and IF
RF and local oscillator
> Through an elimination process, only one answer makes sense.  The input and the output of the radio-frequency amplifier run at the operating frequency.  The output of the RF amplifier constitutes the input to the Mixer.
A-006-002-011    6-2-11
The mixer stage of a superheterodyne receiver:
produces an intermediate frequency
produces spurious signals
acts as a buffer stage
demodulates SSB signals
> The superheterodyne concept is based on converting the operating frequency to a fixed Intermediate Frequency:  the Mixer performs that function by combining the output of the tuneable RF amplifier with the Local Oscillator signal to feed the fixed-tuned Intermediate Frequency chain.
A-006-003-001    6-3-1
What is meant by the noise floor of a receiver?
The weakest signal that can be detected above the receiver internal noise
The weakest signal that can be detected under noisy atmospheric conditions
The minimum level of noise that will overload the receiver RF amplifier stage
The amount of noise generated by the receiver local oscillator
> A receiver's "Noise Floor" is the power level at which an incoming signal exhibits a Signal-To-Noise ratio of zero decibel:  that is, the signal power equals the internal noise power level.  Noise Floor is evaluated while measuring "Minimum Discernible Signal (MDS)".  The "Noise Figure" of a receiver is a comparison of Signal-to-Noise ratio at the input and Signal-to-Noise ratio at the output;  it assesses the degradation in Signal-to-Noise ratio caused by added noise.  A low Noise Figure suggests that little noise was added internally and is a hallmark of sensitivity.  The front-end of the receiver, where signals are weakest, is responsible for the noise performance of a receiver.
A-006-003-002    6-3-2
Which of the following is a purpose of the first IF amplifier stage in a receiver?
To improve selectivity and gain
To tune out cross-modulation distortion
To increase dynamic response
To improve noise figure performance
> The Intermediate Frequency chain is responsible for the selectivity and a large part of the gain.  The front-end of the receiver, where signals are weakest, is responsible for the noise performance of a receiver.
A-006-003-003    6-3-3
How much gain should be used in the RF amplifier stage of a receiver?
Sufficient gain to allow weak signals to overcome noise generated in the first mixer stage
As much gain as possible, short of self-oscillation
It depends on the amplification factor of the first IF stage
Sufficient gain to keep weak signals below the noise of the first mixer stage
> The Radio-Frequency Amplifier should only introduce enough gain to override the internal noise of the subsequent Mixer.  Too much gain will degrade Dynamic Range;  Dynamic Range is broadly defined as a ratio between the strongest signals that can be tolerated near the passband and the "Minimum Discernible Signal".
A-006-003-004    6-3-4
What is the primary purpose of an RF amplifier in a receiver?
To improve the receiver noise figure
To vary the receiver image rejection by using the AGC
To develop the AGC voltage
To provide most of the receiver gain
> The Intermediate Frequency chain is responsible for the selectivity and a large part of the gain.  The front-end of the receiver, where signals are weakest, is responsible for the noise performance of a receiver.
A-006-003-005    6-3-5
How is receiver sensitivity often expressed for UHF FM receivers?
RF level for 12 dB SINAD
RF level for a given Bit Error Rate (BER)
Noise Figure in decibels
Overall gain in decibels
> The SINAD (signal + noise + distortion over noise + distortion) ratio takes the SNR (signal + noise over noise ratio) one step further by including distortion.  A 12 dB SINAD ratio ensures that speech remains intelligible.  Sensitivity expressed in those terms is the lowest RF level that will produce a usable message.  The RF signal generator must be calibrated so the number of microvolts is precisely determined.  Total Harmonic Distortion compares unwanted harmonic components added to the desired fundamental frequency, an audio tone in this instance.
A-006-003-006    6-3-6
What is the term used for the decibel difference (or ratio) between the largest tolerable receiver input signal (without causing audible distortion products) and the minimum discernible signal (sensitivity)?
Dynamic range
Design parameter
Stability
Noise figure
> Dynamic Range is broadly defined as a ratio between the strongest signals that can be tolerated near the passband and the "Minimum Discernible Signal".  The "Noise Figure" of a receiver is a comparison of Signal-to-Noise ratio at the input and Signal-to-Noise ratio at the output;  it assesses the degradation in Signal-to-Noise ratio caused by added noise.  A low Noise Figure suggests that little noise was added internally and is a hallmark of sensitivity.  The front-end of the receiver, where signals are weakest, is responsible for the noise performance of a receiver.
A-006-003-007    6-3-7
The lower the receiver noise figure becomes, the greater will be the receiver's _________:
sensitivity
rejection of unwanted signals
selectivity
stability
> The "Noise Figure" of a receiver is a comparison of Signal-to-Noise ratio at the input and Signal-to-Noise ratio at the output;  it assesses the degradation in Signal-to-Noise ratio caused by added noise.  A low Noise Figure suggests that little noise was added internally and is a hallmark of sensitivity.  The front-end of the receiver, where signals are weakest, is responsible for the noise performance of a receiver.
A-006-003-008    6-3-8
The noise generated in a receiver of good design originates in the:
RF amplifier and mixer
detector and AF amplifier
BFO and detector
IF amplifier and detector
> The "Noise Figure" of a receiver is a comparison of Signal-to-Noise ratio at the input and Signal-to-Noise ratio at the output;  it assesses the degradation in Signal-to-Noise ratio caused by added noise.  A low Noise Figure suggests that little noise was added internally and is a hallmark of sensitivity.  The front-end of the receiver, where signals are weakest, is responsible for the noise performance of a receiver.
A-006-003-009    6-3-9
Why are very low noise figures relatively unimportant for a high frequency receiver?
External HF noise, man-made and natural, are higher than the internal noise generated by the receiver
Ionospheric distortion of the received signal creates high noise levels
The use of SSB and CW on the HF bands overcomes the noise
Regardless of the front end, the succeeding stages when used on HF are very noisy
> Below 30 megahertz, the antenna picks-up atmospheric noise and man-made noise at levels far more important than internal noise.  As the frequency of operation rises, those types of noise become less prevalent.  On Ultra High Frequencies (UHF) and above, the internal noise becomes the limiting factor in receiving weak signals.  The front-end of the receiver, where signals are weakest, is responsible for the noise performance of a receiver:  for weak signal work on 2 metres and up, more attention must be placed on reducing internal noise in the front-end.
A-006-003-010    6-3-10
The term which relates specifically to the amplitude levels of multiple signals that can be accommodated during reception is called:
dynamic range
AGC
cross-modulation index
noise figure
> Dynamic Range is broadly defined as a ratio between the strongest signals that can be tolerated near the passband and the "Minimum Discernible Signal".  Other related notions include Blocking Dynamic Range and Intermodulation Dynamic Range.  Blocking Dynamic Range measures how much of a single strong off-channel signal can be tolerated while receiving a weak signal, it is a measure of desensitization or immunity to overload.  Intermodulation Dynamic Range verifies how strong two off-channel signals can be without spurious responses being generated in the receiver, it is a measure of resistance to intermodulation.
A-006-003-011    6-3-11
Normally, front-end selectivity is provided by the resonant networks both before and after the RF stage in a superheterodyne receiver. This whole section of the receiver is often referred to as the:
preselector
preamble
preamplifier
pass-selector
> A preselector is a tuned stage which passes a desired range of signals to a receiver:  it ensures a certain preliminary selection.  It may or may not be amplified;  in other words, active or passive.
A-006-004-001    6-4-1
What audio shaping network is added at an FM receiver to restore proportionally attenuated lower audio frequencies?
A de-emphasis network
A pre-emphasis network
An audio prescaler
A heterodyne suppressor
> With "true" FM, deviation is independent of modulating frequency, actual deviation is determined solely by the modulating amplitude.  With Phase Modulation, deviation depends on the amount of phase shift and its rapidity, increasing modulating frequency results in proportionally more deviation even if amplitude is held constant.  Because commercial standards were based on Phase Modulation, an FM transmitter requires an artificial boost in high frequency response so that PM and FM sound the same at the receiver.  A pre-emphasis network tailors the frequency response in the FM transmitter.  De-emphasis is employed in the receiver to restore a flat audio response.
A-006-004-002    6-4-2
What does a product detector do?
It mixes an incoming signal with a locally generated carrier
It provides local oscillations for input to a mixer
It amplifies and narrows band-pass frequencies
It detects cross-modulation products
> The Beat Frequency Oscillator feeds the Product Detector for CW and SSB detection.  Mixing the Intermediate Frequency with the BFO signal in the Product Detector produces an audio output.  In Single Sideband, it is said to "reinsert the carrier" as it recreates a reference at the exact frequency at which the carrier, suppressed at the transmitter, would have appeared out of the Intermediate Frequency chain.
A-006-004-003    6-4-3
Distortion in a receiver that only affects strong signals usually indicates a defect in or mis-adjustment of the:
automatic gain control (AGC)
IF amplifier
AF amplifier
RF amplifier
> "Distortion that affects only strong signals is the normal symptom of AGC (Automatic Gain Control) failure." (ARRL Handbook 1985)
A-006-004-004    6-4-4
In a superheterodyne receiver with automatic gain control (AGC), as the strength of the signal increases, the AGC:
reduces the receiver gain
increases the receiver gain
distorts the signal
introduces limiting
> The AGC (Automatic Gain Control) circuit reduces receiver gain as signal strength increases.  AGC can be "IF-derived", some say "RF-Derived" (a slight misnomer), by sampling the output of the last Intermediate Frequency stage or "AF-derived" by sampling the output of the detector.  The resulting control voltage is applied to the Intermediate Frequency amplifiers and, sometimes, Radio-Frequency amplifier.
A-006-004-005    6-4-5
The amplified IF signal is applied to the ____________ stage in a superheterodyne receiver:
detector
RF amplifier
audio output
LO
> Remember your Basic Qualification?  The Detector follows the Intermediate Frequency amplifier.
A-006-004-006    6-4-6
The low-level output of a detector is:
applied to the AF amplifier
grounded via the chassis
fed directly to the speaker
applied to the RF amplifier
> Remember your Basic Qualification?  The Audio Amplifier follows the Detector.
A-006-004-007    6-4-7
The overall output of an AM/CW/SSB receiver can be adjusted by means of manual controls on the receiver or by use of a circuit known as:
automatic gain control
automatic frequency control
inverse gain control
automatic load control
> The AGC (Automatic Gain Control) circuit reduces receiver gain as signal strength increases.  AGC can be "IF-derived", some say "RF-Derived" (a slight misnomer), by sampling the output of the last Intermediate Frequency stage or "AF-derived" by sampling the output of the detector.  The resulting control voltage is applied to the Intermediate Frequency amplifiers and, sometimes, Radio-Frequency amplifier.
A-006-004-008    6-4-8
AGC voltage is applied to the:
RF and IF amplifiers
AF and IF amplifiers
RF and AF amplifiers
detector and AF amplifiers
> The AGC (Automatic Gain Control) circuit reduces receiver gain as signal strength increases.  AGC can be "IF-derived", some say "RF-Derived" (a slight misnomer), by sampling the output of the last Intermediate Frequency stage or "AF-derived" by sampling the output of the detector.  The resulting control voltage is applied to the Intermediate Frequency amplifiers and, sometimes, Radio-Frequency amplifier.
A-006-004-009    6-4-9
AGC is derived in a receiver from one of two circuits. Depending on the method used, it is called:
IF derived or audio derived
RF derived or audio derived
IF derived or RF derived
detector derived or audio derived
> The AGC (Automatic Gain Control) circuit reduces receiver gain as signal strength increases.  AGC can be "IF-derived", some say "RF-Derived" (a slight misnomer), by sampling the output of the last Intermediate Frequency stage or "AF-derived" by sampling the output of the detector.  The resulting control voltage is applied to the Intermediate Frequency amplifiers and, sometimes, Radio-Frequency amplifier.
A-006-004-010    6-4-10
Which two variables primarily determine the behaviour of an automatic gain control (AGC) loop?
Threshold and decay time
Blanking level and slope
Slope and bandwidth
Clipping level and hang time
> The AGC threshold is the level in the monitored circuit at which the AGC circuit begins to reduce gain.  The AGC decay time determines how quickly gain is restored once the strong signal disappears.
A-006-004-011    6-4-11
What circuit combines signals from an IF amplifier stage and a beat-frequency oscillator (BFO), to produce an audio signal?
A product detector circuit
An AGC circuit
A power supply circuit
A VFO circuit
> The Beat Frequency Oscillator feeds the Product Detector for CW and SSB detection.  Mixing the Intermediate Frequency with the BFO signal in the Product Detector produces an audio output.  In Single Sideband, it is said to "reinsert the carrier" as it recreates a reference at the exact frequency at which the carrier, suppressed at the transmitter, would have appeared out of the Intermediate Frequency chain.
A-006-005-001    6-5-1
What part of a superheterodyne receiver determines the image rejection ratio of the receiver?
RF amplifier pre-selector
Product detector
AGC loop
IF filter
> The Image is the other frequency that can successfully mix with the Local Oscillator and produce an output out of the Mixer at the Intermediate frequency.  Selectivity ahead of the Mixer must be employed to prevent that signal from reaching the Mixer.
A-006-005-002    6-5-2
What is the term for the reduction in receiver sensitivity caused by a strong signal near the received frequency?
Desensitization
Cross-modulation interference
Squelch gain rollback
Quieting
> Desensitization is a symptom of front-end overload where a strong adjacent off-channel signal provokes a drop in receiver sensitivity.  The only cure for desensitization is to keep the offending signal out of the receiver.  Other manifestations of front-end overload are intermodulation and cross-modulation where strong signals push the RF amplifier or Mixer into non-linear operation resulting in spurious responses.
A-006-005-003    6-5-3
What causes receiver desensitization?
Strong near frequency signals
Squelch gain adjusted too high
Squelch gain adjusted too low
Audio gain adjusted too low
> Desensitization is a symptom of front-end overload where a strong adjacent off-channel signal provokes a drop in receiver sensitivity.  The only cure for desensitization is to keep the offending signal out of the receiver.  Other manifestations of front-end overload are intermodulation and cross-modulation where strong signals push the RF amplifier or Mixer into non-linear operation resulting in spurious responses.
A-006-005-004    6-5-4
What is one way receiver desensitization can be reduced?
Use a cavity filter
Decrease the receiver squelch gain
Increase the receiver bandwidth
Increase the transmitter audio gain
> Desensitization is a symptom of front-end overload where a strong adjacent off-channel signal provokes a drop in receiver sensitivity.  The only cure for desensitization is to keep the offending signal out of the receiver.  Other manifestations of front-end overload are intermodulation and cross-modulation where strong signals push the RF amplifier or Mixer into non-linear operation resulting in spurious responses.
A-006-005-005    6-5-5
What causes intermodulation in an electronic circuit?
Nonlinear circuits or devices
Too little gain
Positive feedback
Lack of neutralization
> Desensitization is a symptom of front-end overload where a strong adjacent off-channel signal provokes a drop in receiver sensitivity.  The only cure for desensitization is to keep the offending signal out of the receiver.  Other manifestations of front-end overload are intermodulation and cross-modulation where strong signals push the RF amplifier or Mixer into non-linear operation resulting in spurious responses.
A-006-005-006    6-5-6
Which of the following is an important reason for using a VHF intermediate frequency in an HF receiver?
To move the image response far away from the filter passband
To provide a greater tuning range
To tune out cross-modulation distortion
To prevent the generation of spurious mixer products
> Whether injection from the Local Oscillator is above or below the operating frequency, the Image Frequency is always separated from the operating frequency by twice the Intermediate Frequency.  A very high Intermediate Frequency moves the Image well out of the preselector bandpass.
A-006-005-007    6-5-7
Intermodulation interference is produced by:
the mixing of two or more signals in the front-end of a superheterodyne receiver
the interaction of products from high-powered transmitters in the area
the high-voltage stages in the final amplifier of an amplitude or frequency-modulated transmitter
the mixing of more than one signal in the first or second intermediate frequency amplifiers of a receiver
> Desensitization is a symptom of front-end overload where a strong adjacent off-channel signal provokes a drop in receiver sensitivity.  The only cure for desensitization is to keep the offending signal out of the receiver.  Other manifestations of front-end overload are intermodulation and cross-modulation where strong signals push the RF amplifier or Mixer into non-linear operation resulting in spurious responses.
A-006-005-008    6-5-8
Which of the following is NOT a direct cause of instability in a receiver?
Dial display accuracy
Mechanical rigidity
Feedback components
Temperature variations
> Key words:  NOT A DIRECT CAUSE.  Temperature variations, voltage variations and movements due to mechanical stresses will cause changes in frequency.  The selection of feedback components, notably their temperature  coefficient, is paramount for stability.  Dial accuracy is not instability per se.
A-006-005-009    6-5-9
Poor frequency stability in a receiver usually originates in the:
local oscillator and power supply
detector
RF amplifier
mixer
> Stability is the ability to stay on frequency despite other variations.  The Local Oscillator indirectly sets the operating frequency.  Temperature variations, voltage variations and movements due to mechanical stresses will cause changes in frequency.
A-006-005-010    6-5-10
Poor dynamic range of a receiver can cause many problems when a strong signal appears within or near the front-end bandpass. Which of the following is NOT caused as a direct result?
Feedback
Desensitization
Intermodulation
Cross-modulation
> Desensitization is a symptom of front-end overload where a strong adjacent off-channel signal provokes a drop in receiver sensitivity.  The only cure for desensitization is to keep the offending signal out of the receiver.  Other manifestations of front-end overload are intermodulation and cross-modulation where strong signals push the RF amplifier or Mixer into non-linear operation resulting in spurious responses.
A-006-005-011    6-5-11
Which of these measurements is a good indicator of VHF receiver performance in an environment of strong out-of-band signals?
Two-tone Third-Order IMD Dynamic Range, 10 MHz spacing
Third-Order Intercept Point
Blocking Dynamic Range
Intermediate frequency rejection ratio
> "The FM Two-tone, third-order dynamic range, 10-MHz offset ... is a wide-band dynamic-range test on VHF equipment, using two strong signals just outside the amateur band (usually the abode of nearby pager transmitters). (...)  This test is a good indicator of relative IMD performance". (RFI - Intermodulation, ARRL, Ed Hare, W1RFI)

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{L14} Transmission Lines.

A-007-001-001    7-1-1
For an antenna tuner of the "Transformer" type, which of the following statements is FALSE?
The circuit is known as a Pi-type antenna tuner
The input is suitable for 50 ohm impedance
The output is suitable for impedances from low to high
The circuit is known as a transformer-type antenna tuner
> A tuning circuit using two inductively-coupled windings can readily effect an impedance transformation like a transformer.  The coupling may be fixed or variable.  Moving a tap on the output coil changes the turns ratio and permits raising or lowering impedance.
A-007-001-002    7-1-2
For an antenna tuner of the "Series" type, which of the following statements is false?
The circuit is known as a Pi-type antenna tuner
The circuit is known as a Series-type antenna tuner
The output is suitable for impedances from low to high
The input is suitable for impedance of 50 ohms
> A simple series L-C network is one of the ways to couple a random-length antenna, whose impedance can be quite unpredictable, directly to a transmitter.  Other options include the L and Pi networks.
A-007-001-003    7-1-3
For an antenna tuner of the "L" type, which of the following statements is false?
The circuit is suitable for matching to a vertical ground plane antenna
The transmitter input is suitable for 50 ohms impedance
The antenna output is high impedance
The circuit is known as an L-type antenna tuner
> A resonant vertical ground plane antenna offers an impedance in the range 30 to 50 ohms.  A low-pass "L" network (series inductor followed by parallel capacitor) is commonly used with a high impedance random wire.  With only two variables components, an "L" network has a limited range of impedance transformation.  [ In reality, four "L" configurations are possible, two of which can match to a lower impedance. ]
A-007-001-004    7-1-4
For an antenna tuner of the "Pi" type, which of the following statements is false?
The circuit is a series-type antenna tuner
The transmitter input is suitable for impedance of 50 ohms
The antenna output is suitable for impedances from low to high
The circuit is a Pi-type antenna tuner
> The "Pi" configuration, usually an input shunt capacitor, a series inductor and an output shunt capacitor, resembles two L networks back-to-back.  The Pi has greater impedance transformation range than the L network.
A-007-001-005    7-1-5
What is a pi-network?
A network consisting of one inductor and two capacitors or two inductors and one capacitor
An antenna matching network that is isolated from ground
A network consisting of four inductors or four capacitors
A power incidence network
> The "Pi" configuration, usually an input shunt capacitor, a series inductor and an output shunt capacitor, resembles two L networks back-to-back.  The Pi has greater impedance transformation range than the L network.
A-007-001-006    7-1-6
Which type of network offers the greatest transformation ratio?
Pi-network
Chebyshev
Butterworth
L-network
> With only two variables components, an "L" network has a limited range of impedance transformation.  The "Pi" configuration, usually an input shunt capacitor, a series inductor and an output shunt capacitor, resembles two L networks back-to-back.  The Pi has greater impedance transformation range than the L network.  The "Pi-L" network, where the Pi output capacitor doubles as an input capacitor to a subsequent L section, provides even more harmonic suppression and a greater transformation ratio.
A-007-001-007    7-1-7
Why is an L-network of limited utility in impedance matching?
It matches only a small impedance range
It is thermally unstable
It is prone to self-resonance
It has limited power handling capability
> With only two variables components, an "L" network has a limited range of impedance transformation.  The "Pi" configuration, usually an input shunt capacitor, a series inductor and an output shunt capacitor, resembles two L networks back-to-back.  The Pi has greater impedance transformation range than the L network.  The "Pi-L" network, where the Pi output capacitor doubles as an input capacitor to a subsequent L section, provides even more harmonic suppression and a greater transformation ratio.
A-007-001-008    7-1-8
How does a network transform one impedance to another?
It cancels the reactive part of an impedance and changes the resistive part
It produces transconductance to cancel the reactive part of an impedance
It introduces negative resistance to cancel the resistive part of an impedance
Network resistances substitute for load resistances
> Within the context of matching the line to a transmitter, the goal is to present a suitable resistive impedance to the final amplifier.  Impedance comprises a reactive value and a resistive value.  To achieve matching, reactance must be cancelled and resistance transformed.
A-007-001-009    7-1-9
What advantage does a pi-L network have over a pi-network for impedance matching between a vacuum tube linear amplifier and a multiband antenna?
Greater harmonic suppression
Higher efficiency
Lower losses
Greater transformation range
> Key words:  MULTIBAND ANTENNA.  Such an antenna may radiate harmonics more readily.  The added harmonic suppression of the "Pi-L" network is advantageous.
A-007-001-010    7-1-10
Which type of network provides the greatest harmonic suppression?
Pi-L network
Inverse pi-network
Pi-network
L-network
> With only two variables components, an "L" network has a limited range of impedance transformation.  The "Pi" configuration, usually an input shunt capacitor, a series inductor and an output shunt capacitor, resembles two L networks back-to-back.  The Pi has greater impedance transformation range than the L network.  The "Pi-L" network, where the Pi output capacitor doubles as an input capacitor to a subsequent L section, provides even more harmonic suppression and a greater transformation ratio.
A-007-001-011    7-1-11
A Smith Chart is useful:
because it simplifies mathematical operations
only to solve matching and transmission line problems
to solve problems in direct current circuits
because it only works with complex numbers
> "The Smith chart, invented by Phillip H. Smith (1905 1987), is a graphical aid or nomogram designed for electrical and electronics engineers specializing in radio frequency (RF) engineering to assist in solving problems with transmission lines and matching circuits. (...)  The Smith chart is most frequently used at or within the unity radius region.  However, the remainder is still mathematically relevant, being used, for example, in oscillator design and stability analysis". (Wikipedia)
A-007-002-001    7-2-1
What kind of impedance does a quarter wavelength transmission line present to the source when the line is shorted at the far end?
A very high impedance
The same as the characteristic impedance of the transmission line
The same as the output impedance of the source
A very low impedance
> Line lengths that are multiples of a half-wavelength replicate the load impedance at the input regardless of the Characteristic Impedance:  i.e., the input impedance equals the load impedance.  Line lengths that are odd multiples of a quarter-wavelength behave as impedance transformers.  Quarter-wavelength line sections are said to invert impedance:  an open is reflected as a short and vice-versa.  When used for matching right at the antenna, a quarter-wavelength line section is called a "Q Section" or "Quarter-Wave Transformer".
A-007-002-002    7-2-2
What kind of impedance does a quarter wavelength transmission line present to the source if the line is open at the far end?
A very low impedance
A very high impedance
The same as the output impedance of the source
The same as the characteristic impedance of the transmission line
> Line lengths that are multiples of a half-wavelength replicate the load impedance at the input regardless of the Characteristic Impedance:  i.e., the input impedance equals the load impedance.  Line lengths that are odd multiples of a quarter-wavelength behave as impedance transformers.  Quarter-wavelength line sections are said to invert impedance:  an open is reflected as a short and vice-versa.  When used for matching right at the antenna, a quarter-wavelength line section is called a "Q Section" or "Quarter-Wave Transformer".
A-007-002-003    7-2-3
What kind of impedance does a half wavelength transmission line present to the source when the line is open at the far end?
A very high impedance
The same as the characteristic impedance of the transmission line
The same as the output impedance of the source
A very low impedance
> Line lengths that are multiples of a half-wavelength replicate the load impedance at the input regardless of the Characteristic Impedance:  i.e., the input impedance equals the load impedance.  Line lengths that are odd multiples of a quarter-wavelength behave as impedance transformers.  Quarter-wavelength line sections are said to invert impedance:  an open is reflected as a short and vice-versa.  When used for matching right at the antenna, a quarter-wavelength line section is called a "Q Section" or "Quarter-Wave Transformer".
A-007-002-004    7-2-4
What kind of impedance does a half wavelength transmission line present to the source when the line is shorted at the far end?
A very low impedance
A very high impedance
The same as the characteristic impedance of the transmission line
The same as the output impedance of the source
> Line lengths that are multiples of a half-wavelength replicate the load impedance at the input regardless of the Characteristic Impedance:  i.e., the input impedance equals the load impedance.  Line lengths that are odd multiples of a quarter-wavelength behave as impedance transformers.  Quarter-wavelength line sections are said to invert impedance:  an open is reflected as a short and vice-versa.  When used for matching right at the antenna, a quarter-wavelength line section is called a "Q Section" or "Quarter-Wave Transformer".
A-007-002-005    7-2-5
What is the velocity factor of a transmission line?
The velocity of the wave on the transmission line divided by the velocity of light
The velocity of the wave on the transmission line multiplied by the velocity of light in a vacuum
The index of shielding for coaxial cable
The ratio of the characteristic impedance of the line to the terminating impedance
> Velocity Factor is a ratio of wave travel speed on a transmission line with respect to wave speed in vacuum.  It is expressed as a percentage or a decimal fraction because waves travel slower on lines than in space.  The dielectric constant of the insulator between the conductors determines the Velocity Factor per this formula:  1 over the square root of the dielectric constant.  Lines using polyethylene have a Velocity Factor of 66%, foam polyethylene brings it above 80%.  Actual Velocity Factor can vary by as much as plus or minus 10%.  Because of that delay in propagation, a given physical length will always seem longer electrically.
A-007-002-006    7-2-6
What is the term for the ratio of the actual velocity at which a signal travels through a transmission line to the speed of light in a vacuum?
Velocity factor
Characteristic impedance
Surge impedance
Standing wave ratio
> Velocity Factor is a ratio of wave travel speed on a transmission line with respect to wave speed in vacuum.  It is expressed as a percentage or a decimal fraction because waves travel slower on lines than in space.  The dielectric constant of the insulator between the conductors determines the Velocity Factor per this formula:  1 over the square root of the dielectric constant.  Lines using polyethylene have a Velocity Factor of 66%, foam polyethylene brings it above 80%.  Actual Velocity Factor can vary by as much as plus or minus 10%.  Because of that delay in propagation, a given physical length will always seem longer electrically.
A-007-002-007    7-2-7
What is a typical velocity factor for coaxial cable with polyethylene dielectric?
0.66
0.33
0.1
2.7
> Velocity Factor is a ratio of wave travel speed on a transmission line with respect to wave speed in vacuum.  It is expressed as a percentage or a decimal fraction because waves travel slower on lines than in space.  The dielectric constant of the insulator between the conductors determines the Velocity Factor per this formula:  1 over the square root of the dielectric constant.  Lines using polyethylene have a Velocity Factor of 66%, foam polyethylene brings it above 80%.  Actual Velocity Factor can vary by as much as plus or minus 10%.  Because of that delay in propagation, a given physical length will always seem longer electrically.
A-007-002-008    7-2-8
What determines the velocity factor in a transmission line?
Dielectrics in the line
The line length
The centre conductor resistivity
The terminal impedance
> Velocity Factor is a ratio of wave travel speed on a transmission line with respect to wave speed in vacuum.  It is expressed as a percentage or a decimal fraction because waves travel slower on lines than in space.  The dielectric constant of the insulator between the conductors determines the Velocity Factor per this formula:  1 over the square root of the dielectric constant.  Lines using polyethylene have a Velocity Factor of 66%, foam polyethylene brings it above 80%.  Actual Velocity Factor can vary by as much as plus or minus 10%.  Because of that delay in propagation, a given physical length will always seem longer electrically.
A-007-002-009    7-2-9
Why is the physical length of a coaxial cable shorter than its electrical length?
RF energy moves slower along the coaxial cable than in air
The surge impedance is higher in the parallel transmission line
Skin effect is less pronounced in the coaxial cable
The characteristic impedance is higher in a parallel transmission line
> Velocity Factor is a ratio of wave travel speed on a transmission line with respect to wave speed in vacuum.  It is expressed as a percentage or a decimal fraction because waves travel slower on lines than in space.  The dielectric constant of the insulator between the conductors determines the Velocity Factor per this formula:  1 over the square root of the dielectric constant.  Lines using polyethylene have a Velocity Factor of 66%, foam polyethylene brings it above 80%.  Actual Velocity Factor can vary by as much as plus or minus 10%.  Because of that delay in propagation, a given physical length will always seem longer electrically.
A-007-002-010    7-2-10
The reciprocal of the square root of the dielectric constant of the material used to separate the conductors in a transmission line gives the ____________ of the line:
velocity factor
VSWR
impedance
hermetic losses
> Velocity Factor is a ratio of wave travel speed on a transmission line with respect to wave speed in vacuum.  It is expressed as a percentage or a decimal fraction because waves travel slower on lines than in space.  The dielectric constant of the insulator between the conductors determines the Velocity Factor per this formula:  1 over the square root of the dielectric constant.  Lines using polyethylene have a Velocity Factor of 66%, foam polyethylene brings it above 80%.  Actual Velocity Factor can vary by as much as plus or minus 10%.  Because of that delay in propagation, a given physical length will always seem longer electrically.
A-007-002-011    7-2-11
The velocity factor of a transmission line is the:
ratio of the velocity of propagation in the transmission line to the velocity of propagation in free space
impedance of the line, e.g. 50 ohm, 75 ohm, etc.
speed at which the signal travels in free space
speed to which the standing waves are reflected back to the transmitter
> Velocity Factor is a ratio of wave travel speed on a transmission line with respect to wave speed in vacuum.  It is expressed as a percentage or a decimal fraction because waves travel slower on lines than in space.  The dielectric constant of the insulator between the conductors determines the Velocity Factor per this formula:  1 over the square root of the dielectric constant.  Lines using polyethylene have a Velocity Factor of 66%, foam polyethylene brings it above 80%.  Actual Velocity Factor can vary by as much as plus or minus 10%.  Because of that delay in propagation, a given physical length will always seem longer electrically.

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A-007-009-001    7-9-1
Waveguide is typically used:
at frequencies above 3000 MHz
at frequencies above 2 MHz
at frequencies below 150 MHz
at frequencies below 1500 MHz
> Waveguides, used as transmission lines, are hollow pipes through which signals propagate as waves.  The width or diameter of the waveguide must be slightly larger than a half-wavelength at the operating frequency.  Below one gigahertz, dimensions become prohibitive.  Signals with wavelengths too large for the physical size of the waveguide are attenuated:  waveguides behave like high-pass filters, in other words, attenuation below the cutoff frequency.  Waveguides do not suffer the conduction, dielectric or radiation losses that normal transmission lines present at microwave frequencies.
A-007-009-002    7-9-2
Which of the following is not correct? Waveguide is an efficient transmission medium because it features:
low hysteresis loss
low radiation loss
low dielectric loss
low copper loss
> Waveguides, used as transmission lines, are hollow pipes through which signals propagate as waves.  The width or diameter of the waveguide must be slightly larger than a half-wavelength at the operating frequency.  Below one gigahertz, dimensions become prohibitive.  Signals with wavelengths too large for the physical size of the waveguide are attenuated:  waveguides behave like high-pass filters, in other words, attenuation below the cutoff frequency.  Waveguides do not suffer the conduction, dielectric or radiation losses that normal transmission lines present at microwave frequencies.
A-007-009-003    7-9-3
Which of the following is an advantage of waveguide as a transmission line?
Low loss
Frequency sensitive based on dimensions
Expensive
Heavy and difficult to install
> Waveguides, used as transmission lines, are hollow pipes through which signals propagate as waves.  The width or diameter of the waveguide must be slightly larger than a half-wavelength at the operating frequency.  Below one gigahertz, dimensions become prohibitive.  Signals with wavelengths too large for the physical size of the waveguide are attenuated:  waveguides behave like high-pass filters, in other words, attenuation below the cutoff frequency.  Waveguides do not suffer the conduction, dielectric or radiation losses that normal transmission lines present at microwave frequencies.
A-007-009-004    7-9-4
For rectangular waveguide to transfer energy, the cross-section should be at least:
one-half wavelength
three-eighths wavelength
one-eighth wavelength
one-quarter wavelength
> Waveguides, used as transmission lines, are hollow pipes through which signals propagate as waves.  The width or diameter of the waveguide must be slightly larger than a half-wavelength at the operating frequency.  Below one gigahertz, dimensions become prohibitive.  Signals with wavelengths too large for the physical size of the waveguide are attenuated:  waveguides behave like high-pass filters, in other words, attenuation below the cutoff frequency.  Waveguides do not suffer the conduction, dielectric or radiation losses that normal transmission lines present at microwave frequencies.
A-007-009-005    7-9-5
Which of the following statements about waveguide IS NOT correct?
Waveguide has high loss at high frequencies, but low loss below cutoff frequency
In the transverse electric mode, a component of the magnetic field is in the direction of propagation
In the transverse magnetic mode, a component of the electric field is in the direction of propagation
Waveguide has low loss at high frequencies, but high loss below cutoff frequency
> Key words:  IS NOT.  Signals with wavelengths too large for the physical size of the waveguide are attenuated:  waveguides behave like high-pass filters, in other words, attenuation below the cutoff frequency.  In free space, waves are known as transverse-electromagnetic: the electric field, the magnetic field and the direction of travel are all perpendicular to one another.  In a waveguide, waves bounce from wall to wall thus travelling in a zigzag manner.  Only one of the electric or magnetic field can be truly perpendicular with the length of the waveguide;  the mode, transverse electric or transverse magnetic, describes which field is purely perpendicular.
A-007-009-006    7-9-6
Which of the following is a major advantage of waveguide over coaxial cable for use at microwave frequencies?
Very low losses
Frequency response from 1.8 MHz to 24GHz
Easy to install
Inexpensive to install
> Waveguides, used as transmission lines, are hollow pipes through which signals propagate as waves.  The width or diameter of the waveguide must be slightly larger than a half-wavelength at the operating frequency.  Below one gigahertz, dimensions become prohibitive.  Signals with wavelengths too large for the physical size of the waveguide are attenuated:  waveguides behave like high-pass filters, in other words, attenuation below the cutoff frequency.  Waveguides do not suffer the conduction, dielectric or radiation losses that normal transmission lines present at microwave frequencies.
A-007-009-007    7-9-7
What is printed circuit transmission line called?
Microstripline
Dielectric substrate
Dielectric imprinting
Ground plane
> A Microstrip transmission line is a type of line consisting of a thin and flat strip of conductive material separated from a ground plane by a dielectric.  A double-sided printed circuit board lends itself to the construction of microstrip lines:  traces on top with a ground plane underneath.  Characteristic Impedance is determined by trace width, dielectric thickness and dielectric constant.  One side of the line is exposed to air, external shielding may be required when high isolation is required.  Stripline uses a similar thin and flat conductor but sandwiched between two parallel ground planes.
A-007-009-008    7-9-8
Compared with coaxial cable, microstripline:
has poorer shielding
has superior shielding
must have much lower characteristic impedance
must have much higher characteristic impedance
> A Microstrip transmission line is a type of line consisting of a thin and flat strip of conductive material separated from a ground plane by a dielectric.  A double-sided printed circuit board lends itself to the construction of microstrip lines:  traces on top with a ground plane underneath.  Characteristic Impedance is determined by trace width, dielectric thickness and dielectric constant.  One side of the line is exposed to air, external shielding may be required when high isolation is required.  Stripline uses a similar thin and flat conductor but sandwiched between two parallel ground planes.
A-007-009-009    7-9-9
A section of waveguide:
operates like a high-pass filter
operates like a low-pass filter
operates like a band-stop filter
is lightweight and easy to install
> Waveguides, used as transmission lines, are hollow pipes through which signals propagate as waves.  The width or diameter of the waveguide must be slightly larger than a half-wavelength at the operating frequency.  Below one gigahertz, dimensions become prohibitive.  Signals with wavelengths too large for the physical size of the waveguide are attenuated:  waveguides behave like high-pass filters, in other words, attenuation below the cutoff frequency.  Waveguides do not suffer the conduction, dielectric or radiation losses that normal transmission lines present at microwave frequencies.
A-007-009-010    7-9-10
Stripline is a:
printed circuit transmission line
small semiconductor family
high power microwave antenna
family of fluids for removing coatings from small parts
> A Microstrip transmission line is a type of line consisting of a thin and flat strip of conductive material separated from a ground plane by a dielectric.  A double-sided printed circuit board lends itself to the construction of microstrip lines:  traces on top with a ground plane underneath.  Characteristic Impedance is determined by trace width, dielectric thickness and dielectric constant.  External shielding may be required when high isolation is required.  Stripline uses a similar thin and flat conductor but sandwiched between two parallel ground planes.
A-007-009-011    7-9-11
What precautions should you take before beginning repairs on a microwave feed horn or waveguide?
Be sure the transmitter is turned off and the power source is disconnected
Be sure the weather is dry and sunny
Be sure propagation conditions are unfavourable for tropospheric ducting
Be sure to wear tight-fitting clothes and gloves to protect your body and hands from sharp edges
> With the possibility of shorter wavelengths to reach deeper into the body or to produce resonances in smaller structures, such as the eye, be extra careful not to expose anyone to microwave radiation.  The significant gain available from physically small antennas also turn low power levels into definite risks.  Heating is one known effect of RF on body tissues, other effects are possible.

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{L15} Antennas.

A-007-003-001    7-3-1
What term describes a method used to match a high-impedance transmission line to a lower impedance antenna by connecting the line to the driven element in two places, spaced a fraction of a wavelength on each side of the driven element centre?
The T match
The gamma match
The omega match
The stub match
> Gamma match: an unbalanced feed system, the coaxial braid attaches to the centre of the radiating element, the centre conductor connects via a series capacitor further along the radiating element.  This second connection is done with an adjustable rod parallel to the radiating element.  T match: a balanced feed system, can be thought as two mirrored gamma matches, the feed line is brought via conductors parallel to the radiating element at points further along the element.  A Matching Stub is a short section of line, open or shorted, connected across the transmission line at a specific distance from the antenna feedpoint.
A-007-003-002    7-3-2
What term describes an unbalanced feed system in which the driven element of an antenna is fed both at the centre and a fraction of a wavelength to one side of centre?
The gamma match
The omega match
The stub match
The T match
> Gamma match: an unbalanced feed system, the coaxial braid attaches to the centre of the radiating element, the centre conductor connects via a series capacitor further along the radiating element.  This second connection is done with an adjustable rod parallel to the radiating element.  T match: a balanced feed system, can be thought as two mirrored gamma matches, the feed line is brought via conductors parallel to the radiating element at points further along the element.  A Matching Stub is a short section of line, open or shorted, connected across the transmission line at a specific distance from the antenna feedpoint.
A-007-003-003    7-3-3
What term describes a method of antenna impedance matching that uses a short section of transmission line connected to the antenna transmission line near the antenna and perpendicular to the transmission line?
The stub match
The omega match
The delta match
The gamma match
> Gamma match: an unbalanced feed system, the coaxial braid attaches to the centre of the radiating element, the centre conductor connects via a series capacitor further along the radiating element.  This second connection is done with an adjustable rod parallel to the radiating element.  T match: a balanced feed system, can be thought as two mirrored gamma matches, the feed line is brought via conductors parallel to the radiating element at points further along the element.  A Matching Stub is a short section of line, open or shorted, connected across the transmission line at a specific distance from the antenna feedpoint.
A-007-003-004    7-3-4
Assuming a velocity factor of 0.66 what would be the physical length of a typical coaxial stub that is electrically one quarter wavelength long at 14.1 MHz?
3.51 metres (11.5 feet)
20 metres (65.6 feet)
2.33 metres (7.64 feet)
0.25 metre (0.82 foot)
> An electrical quarter wavelength can be computed in metres as one fourth of 300 divided by frequency in megahertz.  The physical length equals the electrical length times the Velocity Factor.  In this example, 300 divided by 14.1 divided by 4 times 0.66 = 3.51 metre.
A-007-003-005    7-3-5
The driven element of a Yagi antenna is connected to a coaxial transmission line. The coax braid is connected to the centre of the driven element and the centre conductor is connected to a variable capacitor in series with an adjustable mechanical arrangement on one side of the driven element. The type of matching is:
gamma match
lambda match
T match
zeta match
> Gamma match: an unbalanced feed system, the coaxial braid attaches to the centre of the radiating element, the centre conductor connects via a series capacitor further along the radiating element.  This second connection is done with an adjustable rod parallel to the radiating element.  T match: a balanced feed system, can be thought as two mirrored gamma matches, the feed line is brought via conductors parallel to the radiating element at points further along the element.  A Matching Stub is a short section of line, open or shorted, connected across the transmission line at a specific distance from the antenna feedpoint.
A-007-003-006    7-3-6
A quarter-wave stub, for use at 15 MHz, is made from a coaxial cable having a velocity factor of 0.8. Its physical length will be:
4 m (13.1 ft)
12 m (39.4 ft)
8 m (26.2 ft)
7.5 m (24.6 ft)
> An electrical quarter wavelength can be computed in metres as one fourth of 300 divided by frequency in megahertz.  The physical length equals the electrical length times the Velocity Factor.  In this example, 300 divided by 15 divided by 4 times 0.80 = 4 metres.
A-007-003-007    7-3-7
The matching of a driven element with a single adjustable mechanical and capacitive arrangement is descriptive of:
a "gamma" match
a "T" match
an "omega" match
a "Y" match
> Gamma match: an unbalanced feed system, the coaxial braid attaches to the centre of the radiating element, the centre conductor connects via a series capacitor further along the radiating element.  This second connection is done with an adjustable rod parallel to the radiating element.  T match: a balanced feed system, can be thought as two mirrored gamma matches, the feed line is brought via conductors parallel to the radiating element at points further along the element.  A Matching Stub is a short section of line, open or shorted, connected across the transmission line at a specific distance from the antenna feedpoint.
A-007-003-008    7-3-8
A Yagi antenna uses a gamma match. The coaxial braid connects to:
the centre of the driven element
the variable capacitor
the adjustable gamma rod
the centre of the reflector
> Gamma match: an unbalanced feed system, the coaxial braid attaches to the centre of the radiating element, the centre conductor connects via a series capacitor further along the radiating element.  This second connection is done with an adjustable rod parallel to the radiating element.  T match: a balanced feed system, can be thought as two mirrored gamma matches, the feed line is brought via conductors parallel to the radiating element at points further along the element.  A Matching Stub is a short section of line, open or shorted, connected across the transmission line at a specific distance from the antenna feedpoint.
A-007-003-009    7-3-9
A Yagi antenna uses a gamma match. The centre of the driven element connects to:
the coaxial line braid
the coaxial line centre conductor
the adjustable gamma rod
a variable capacitor
> Gamma match: an unbalanced feed system, the coaxial braid attaches to the centre of the radiating element, the centre conductor connects via a series capacitor further along the radiating element.  This second connection is done with an adjustable rod parallel to the radiating element.  T match: a balanced feed system, can be thought as two mirrored gamma matches, the feed line is brought via conductors parallel to the radiating element at points further along the element.  A Matching Stub is a short section of line, open or shorted, connected across the transmission line at a specific distance from the antenna feedpoint.
A-007-003-010    7-3-10
A Yagi antenna uses a gamma match. The adjustable gamma rod connects to:
the variable capacitor
the coaxial line centre conductor
an adjustable point on the reflector
the centre of the driven element
> Gamma match: an unbalanced feed system, the coaxial braid attaches to the centre of the radiating element, the centre conductor connects via a series capacitor further along the radiating element.  This second connection is done with an adjustable rod parallel to the radiating element.  T match: a balanced feed system, can be thought as two mirrored gamma matches, the feed line is brought via conductors parallel to the radiating element at points further along the element.  A Matching Stub is a short section of line, open or shorted, connected across the transmission line at a specific distance from the antenna feedpoint.
A-007-003-011    7-3-11
A Yagi antenna uses a gamma match. The variable capacitor connects to the:
adjustable gamma rod
an adjustable point on the director
center of the driven element
coaxial line braid
> Gamma match: an unbalanced feed system, the coaxial braid attaches to the centre of the radiating element, the centre conductor connects via a series capacitor further along the radiating element.  This second connection is done with an adjustable rod parallel to the radiating element.  T match: a balanced feed system, can be thought as two mirrored gamma matches, the feed line is brought via conductors parallel to the radiating element at points further along the element.  A Matching Stub is a short section of line, open or shorted, connected across the transmission line at a specific distance from the antenna feedpoint.
A-007-004-001    7-4-1
In a half-wave dipole, the distribution of _______ is highest at each end.
voltage
current
inductance
capacitance
> On a centre-fed resonant half-wave dipole, current is high and voltage low at the feedpoint, the ends exhibit high voltage and low current.  Low voltage and high current at the centre make for low impedance ( Z = E divided by I ).
A-007-004-002    7-4-2
In a half-wave dipole, the distribution of _______ is lowest at each end.
current
voltage
inductance
capacitance
> On a centre-fed resonant half-wave dipole, current is high and voltage low at the feedpoint, the ends exhibit high voltage and low current.  Low voltage and high current at the centre make for low impedance ( Z = E divided by I ).
A-007-004-003    7-4-3
The feed point in a centre-fed half-wave antenna is at the point of:
maximum current
minimum current
minimum voltage and current
maximum voltage
> On a centre-fed resonant half-wave dipole, current is high and voltage low at the feedpoint, the ends exhibit high voltage and low current.  Low voltage and high current at the centre make for low impedance ( Z = E divided by I ).
A-007-004-004    7-4-4
In a half-wave dipole, the lowest distribution of _________ occurs at the middle.
voltage
capacity
inductance
current
> On a centre-fed resonant half-wave dipole, current is high and voltage low at the feedpoint, the ends exhibit high voltage and low current.  Low voltage and high current at the centre make for low impedance ( Z = E divided by I ).
A-007-004-005    7-4-5
In a half-wave dipole, the highest distribution of ________ occurs at the middle.
current
inductance
voltage
capacity
> On a centre-fed resonant half-wave dipole, current is high and voltage low at the feedpoint, the ends exhibit high voltage and low current.  Low voltage and high current at the centre make for low impedance ( Z = E divided by I ).
A-007-004-006    7-4-6
A half-wave dipole antenna is normally fed at the point where:
the current is maximum
the voltage is maximum
the resistance is maximum
the antenna is resonant
> On a centre-fed resonant half-wave dipole, current is high and voltage low at the feedpoint, the ends exhibit high voltage and low current.  Low voltage and high current at the centre make for low impedance ( Z = E divided by I ).
A-007-004-007    7-4-7
At the ends of a half-wave dipole:
voltage is high and current is low
voltage and current are both high
voltage and current are both low
voltage is low and current is high
> On a centre-fed resonant half-wave dipole, current is high and voltage low at the feedpoint, the ends exhibit high voltage and low current.  Low voltage and high current at the centre make for low impedance ( Z = E divided by I ).
A-007-004-008    7-4-8
The impedance of a half-wave antenna at its centre is low, because at this point:
voltage is low and current is high
voltage and current are both high
voltage and current are both low
voltage is high and current is low
> On a centre-fed resonant half-wave dipole, current is high and voltage low at the feedpoint, the ends exhibit high voltage and low current.  Low voltage and high current at the centre make for low impedance ( Z = E divided by I ).
A-007-004-009    7-4-9
In a half-wave dipole, where does minimum voltage occur?
The centre
At the right end
It is equal at all points
Both ends
> On a centre-fed resonant half-wave dipole, current is high and voltage low at the feedpoint, the ends exhibit high voltage and low current.  Low voltage and high current at the centre make for low impedance ( Z = E divided by I ).
A-007-004-010    7-4-10
In a half-wave dipole, where does the minimum current occur?
At both ends
At the centre
It is equal at all points
At the right end
> On a centre-fed resonant half-wave dipole, current is high and voltage low at the feedpoint, the ends exhibit high voltage and low current.  Low voltage and high current at the centre make for low impedance ( Z = E divided by I ).
A-007-004-011    7-4-11
In a half-wave dipole, where does the minimum impedance occur?
At the centre
It is the same at all points
At the right end
At both ends
> On a centre-fed resonant half-wave dipole, current is high and voltage low at the feedpoint, the ends exhibit high voltage and low current.  Low voltage and high current at the centre make for low impedance ( Z = E divided by I ).
A-007-005-001    7-5-1
What is meant by circularly polarized electromagnetic waves?
Waves with a rotating electric field
Waves with an electric field bent into circular shape
Waves that circle the earth
Waves produced by a circular loop antenna
> The polarization of an electromagnetic radio wave corresponds to the position of the electrical field with respect to the surface of the Earth:  horizontal when the E field is parallel to ground and vertical when perpendicular to ground.  The magnetic field is at 90 degrees (perpendicular) to the electrical field.  Dipoles and Yagis are linearly polarized antennas (i.e., the electrical field has a constant orientation).  Circular polarization, where the polarization rotates, can be obtained from helical beam antennas or with crossed linear antennas fed with the correct phase difference.  "Sense" refers to the direction of the rotation:  clockwise polarization for a receding wave is termed right-hand.
A-007-005-002    7-5-2
What type of polarization is produced by crossed dipoles fed 90 degrees out of phase?
Circular polarization
Cross-polarization
Perpendicular polarization
None of the other answers, the two fields cancel out
> Crossed dipoles fed 90 degrees out of phase are the active elements of a turnstile antenna and produce circular polarization.  The turnstile antenna is used for satellite communications.
A-007-005-003    7-5-3
Which of these antennas does not produce circular polarization?
Loaded helical-wound antenna
Crossed dipoles fed 90 degrees out of phase
Lindenblad antenna
Axial-mode helical antenna
> Key word:  NOT.  Antennas featuring a fine wire wound around a shaft (e.g., HF mobile antennas) are "loaded helical-wound antennas"; these produce a linear polarization, i.e., vertical or horizontal depending on their positions relative to ground.  The axial-mode helical antenna, with its corkscrew look, is used in satellite work and produces circular polarization.
A-007-005-004    7-5-4
On VHF/UHF frequencies, Doppler shift becomes of consequence on which type of communication?
Contact via satellite
Contact through a hilltop repeater
Simplex line-of-sight contact between hand-held transceivers
Contact with terrestrial mobile stations
> "Doppler shift: the change in frequency of a received signal due to the motion of the satellite.  This requires adjustment of the transmit or receive frequency, with the common practice being to change the higher of the two frequencies in use" (http://www.amsat.org/).  Low Earth orbiting satellites travel at speeds around 28 000 km/h.  The higher the operating frequency, the higher the possible shift: for example, +/- 600 Hz on 10 m, +/- 3 kHz on 2 m and +/- 9 kHz on 70 cm.
A-007-005-005    7-5-5
For VHF and UHF signals over a fixed path, what extra loss can be expected when linearly-polarized antennas are crossed-polarized (90 degrees)?
20 dB or more
3 dB
6 dB
10 dB
> "A loss in signal strength of 20 dB or more can be expected with cross-polarization so it is important to use antennas with the same polarization as the stations with which you expect to communicate."  (ARRL Antenna Book, 22nd ed., section 21.10.5 Polarization)
A-007-005-006    7-5-6
Which of the following is NOT a valid parabolic dish illumination arrangement?
Newtonian
Front feed
Offset feed
Cassegrain
> Key word: NOT.  Front feed (also known as focal feed or axial feed): circular reflector, the feed is centered in front of the reflector, very common on larger dish antennas.  Offset feed (also known as off-axis): elliptical reflector, the feed is off to one side, out of the path of the radio waves, typical of domestic satellite receiving antennas.  Cassegrain (based on the Cassegrain telescope): the feed is behind the dish and relies on a small convex secondary reflector in front of the dish.  Newtonian: a bogus answer, valid for telescopes.
A-007-005-007    7-5-7
A parabolic antenna is very efficient because:
all the received energy is focused to a point where the pick-up antenna is located
a dipole antenna can be used to pick up the received energy
no impedance matching is required
a horn-type radiator can be used to trap the received energy
> A parabolic reflector dish provides significant gain because energy striking any point of the parabola is reflected to the focal point with the correct phase.  On transmit, the inverse process takes place:  all energy directed at the parabola from the feed antenna is reflected forward with the correct phase.  High gain antennas used on UHF or microwave frequencies present a real risk to living tissues:  never stand in front of a transmitting antenna.
A-007-005-008    7-5-8
A helical-beam antenna with right-hand polarization will best receive signals with:
right-hand polarization
left-hand polarization
vertical polarization only
horizontal polarization
> The helical beam antenna is circularly polarized.  Although it will respond to horizontally or vertically polarized waves, the full gain of the antenna can only be realized with a circularly polarized wave of the same "sense".
A-007-005-009    7-5-9
One antenna which will respond simultaneously to vertically- and horizontally-polarized signals is the:
helical-beam antenna
folded dipole antenna
ground-plane antenna
quad antenna
> The dipole, ground-plane and quad are all linearly polarized and thus respond optimally to waves polarized in a single given direction, horizontal or vertical as the case may be.  Unless proper alignment is assured, a significant loss is incurred.  The helical beam antenna is circularly polarized, it can deal with the rotating fields of a wave with circular polarization.  Consequently, it can deal with any single polarization at any given angle.
A-007-005-010    7-5-10
In amateur work, what is the surface error upper limit you should try not to exceed on a parabolic reflector?
0.1 lambda
0.25 lambda
5 mm (0.2 in) regardless of frequency
1% of the diameter
> "Surface errors should not exceed 1/8 lambda in amateur operation.  At 430 MHz, 1/8 lambda is 3.4 inches [8.6 cm], but at 10 GHz, it is 0.1476 inch [3.7 mm]! (...)  Mesh can be used for the reflector surface to reduce weight and wind loading, but hole size should be less than 1/12 lambda." (ARRL Antenna Book 22nd ed., sect. 15.6.2)
A-007-005-011    7-5-11
You want to convert a surplus parabolic dish for amateur radio use, the gain of this antenna depends on:
the diameter of the antenna in wavelengths
the polarization of the feed device illuminating it
the focal length of the antenna
the material composition of the dish
> Gain is primarily affected by the antenna aperture (reflector area) to wavelength ratio.
A-007-006-001    7-6-1
A transmitter has an output of 100 watts. The cable and connectors have a composite loss of 3 dB, and the antenna has a gain of 6 dBd. What is the Effective Radiated Power?
200 watts
350 watts
400 watts
300 watts
> Effective Radiated Power (ERP) equals transmitter power minus line losses plus antenna gain.  In this example, minus 3 dB plus 6 dB yields a net increase of 3 dB or twice the power.
A-007-006-002    7-6-2
As standing wave ratio rises, so does the loss in the transmission line. This is caused by:
dielectric and conductor heat losses
high antenna currents
high antenna voltage
leakage to ground through the dielectric
> Voltage peaks on the standing wave increase losses through the dielectric ( P = E squared divided by R ), current peaks on the standing wave increase conductor losses ( P = I squared times R ).
A-007-006-003    7-6-3
What is the Effective Radiated Power of an amateur transmitter, if the transmitter output power is 200 watts, the transmission line loss is 5 watts, and the antenna power gain is 3 dBd?
390 watts
197 watts
228 watts
178 watts
> Effective Radiated Power (ERP) equals transmitter power minus line losses plus antenna gain.  In this example, minus 5 watts plus 3 dB yields a net increase of 3 dB or twice the remaining power of 195 watts.
A-007-006-004    7-6-4
Effective Radiated Power means the:
transmitter output power, minus line losses, plus antenna gain relative to a dipole
power supplied to the antenna before the modulation of the carrier
power supplied to the transmission line plus antenna gain
ratio of signal output power to signal input power
> Effective Radiated Power (ERP) equals transmitter power minus line losses plus antenna gain.
A-007-006-005    7-6-5
A transmitter has an output power of 200 watts. The coaxial and connector losses are 3 dB in total, and the antenna gain is 9 dBd. What is the approximate Effective Radiated Power of this system?
800 watts
3200 watts
1600 watts
400 watts
> Effective Radiated Power (ERP) equals transmitter power minus line losses plus antenna gain.  In this example, minus 3 dB plus 9 dB yields a net increase of 6 dB or four times the power.
A-007-006-006    7-6-6
A transmitter has a power output of 100 watts. There is a loss of 1.30 dB in the transmission line, a loss of 0.2 dB through the antenna tuner, and a gain of 4.50 dBd in the antenna. The Effective Radiated Power (ERP) is:
200 watts
800 watts
400 watts
100 watts
> Effective Radiated Power (ERP) equals transmitter power minus line losses plus antenna gain.  In this example, minus 1.5 dB plus 4.5 dB yields a net increase of 3 dB or twice the power.
A-007-006-007    7-6-7
If the overall gain of an amateur station is increased by 3 dB the ERP (Effective Radiated Power) will:
double
decrease by 3 watts
remain the same
be cut in half
> Effective Radiated Power (ERP) equals transmitter power minus line losses plus antenna gain.  In this example, a net gain of 3 dB yields twice the power.
A-007-006-008    7-6-8
A transmitter has a power output of 125 watts. There is a loss of 0.8 dB in the transmission line, 0.2 dB in the antenna tuner, and a gain of 10 dBd in the antenna. The Effective Radiated Power (ERP) is:
1000
1250
1125
134
> Effective Radiated Power (ERP) equals transmitter power minus line losses plus antenna gain.  In this example, minus 1 dB plus 10 dB yields a net increase of 9 dB or eight times the power.
A-007-006-009    7-6-9
If a 3 dBd gain antenna is replaced with a 9 dBd gain antenna, with no other changes, the Effective Radiated Power (ERP) will increase by:
4
6
1.5
2
> Effective Radiated Power (ERP) equals transmitter power minus line losses plus antenna gain.  In this example, an added 6 dB yields four times the power.
A-007-006-010    7-6-10
A transmitter has an output of 2000 watts PEP. The transmission line, connectors and antenna tuner have a composite loss of 1 dB, and the gain from the stacked Yagi antenna is 10 dBd. What is the Effective Radiated Power (ERP) in watts PEP?
16 000
18 000
20 000
2009
> Effective Radiated Power (ERP) equals transmitter power minus line losses plus antenna gain.  In this example, minus 1 dB plus 10 dB yields a net increase of 9 dB or eight times the power.
A-007-006-011    7-6-11
A transmitter has an output of 1000 watts PEP. The coaxial cable, connectors and antenna tuner have a composite loss of 1 dB, and the antenna gain is 10 dBd. What is the Effective Radiated Power (ERP) in watts PEP?
8000
1009
10 000
9000
> Effective Radiated Power (ERP) equals transmitter power minus line losses plus antenna gain.  In this example, minus 1 dB plus 10 dB yields a net increase of 9 dB or eight times the power.
A-007-007-001    7-7-1
For a 3-element Yagi antenna with horizontally mounted elements, how does the main lobe takeoff angle vary with height above flat ground?
It decreases with increasing height
It increases with increasing height
It does not vary with height
It depends on E-region height, not antenna height
> Greater antenna heights tend to lower the main radiation lobe where ground reflections end up in phase with direct radiation from the antenna.
A-007-007-002    7-7-2
Most simple horizontally polarized antennas do not exhibit significant directivity unless they are:
a half wavelength or more above the ground
an eighth of a wavelength above the ground
a quarter wavelength above the ground
three-eighths of a wavelength above the ground
> Below one half-wavelength in antenna height, there is little point in selecting a given broadside direction:  for example, choosing a north-south orientation to favour east-west radiation will not pay significant dividends for antennas close to ground.
A-007-007-003    7-7-3
The plane from which ground reflections can be considered to take place, or the effective ground plane for an antenna is:
several centimeters to as much as 2 meters below ground, depending upon soil conditions
as much as 6 cm below ground depending upon soil conditions
as much as a meter above ground
at ground level exactly
> Current penetration around an antenna depends first on frequency and then on soil conductivity and dielectric constant.  At HF frequencies over salt water, penetration ranges from 5 to 18 centimetres.  Over poor ground, penetration can exceed 10 metres.
A-007-007-004    7-7-4
Why is a ground-mounted vertical quarter-wave antenna in reasonably open surroundings better for long distance contacts than a half-wave dipole at a quarter wavelength above ground?
The vertical radiation angle is lower
The radiation resistance is lower
It has an omnidirectional characteristic
It uses vertical polarization
> Key words:  DIPOLE AT A QUARTER WAVELENGTH HEIGHT.  At heights below three eights of a wavelength, ground reflections cause horizontal dipoles to direct more energy straight up.  At a height of one half-wavelength, radiation at 90 degrees is minimized and two lobes form at 30 degrees.  In this comparison, the ground-mounted vertical undoubtedly exhibits a lower radiation angle as it cannot possibly radiate upwards.
A-007-007-005    7-7-5
When a half-wave dipole antenna is installed one-half wavelength above ground, the:
vertical or upward radiation is effectively cancelled
radiation pattern changes to produce side lobes at 15 and 50 degrees
side lobe radiation is cancelled
radiation pattern is unaffected
> At heights below three eights of a wavelength, ground reflections cause horizontal dipoles to direct more energy straight up.  At a height of one half-wavelength, radiation at 90 degrees is minimized and two lobes form at 30 degrees.
A-007-007-006    7-7-6
How does antenna height affect the horizontal (azimuthal) radiation pattern of a horizontal dipole HF antenna?
If the antenna is less than one-half wavelength high, reflected radio waves from the ground significantly distort the pattern
Antenna height has no effect on the pattern
If the antenna is less than one-half wavelength high, radiation off the ends of the wire is eliminated
If the antenna is too high, the pattern becomes unpredictable
> Below one half-wavelength in antenna height, there is little point in selecting a given broadside direction:  for example, choosing a north-south orientation to favour east-west radiation will not pay significant dividends for antennas close to ground.
A-007-007-007    7-7-7
For long distance propagation, the vertical radiation angle of the energy from the antenna should be:
less than 30 degrees
more than 45 degrees but less than 90 degrees
90 degrees
more than 30 degrees but less than 45 degrees
> Depending on band (for example, 10, 15 and 20 metre) and distance, preferred radiation angles range from 1 to 25 degrees for long distance communication.  A low radiation angle permits hitting the ionosphere at a greater distance for longer skip distances.
A-007-007-008    7-7-8
Greater distance can be covered with multiple-hop transmissions by decreasing the:
vertical radiation angle of the antenna
power applied to the antenna
main height of the antenna
length of the antenna
> Depending on band (for example, 10, 15 and 20 metre) and distance, preferred radiation angles range from 1 to 25 degrees for long distance communication.  A low radiation angle permits hitting the ionosphere at a greater distance for longer skip distances.
A-007-007-009    7-7-9
The impedance at the centre of a dipole antenna more than 3 wavelengths above ground would be nearest to:
75 ohms
25 ohms
300 ohms
600 ohms
> The impedance of a dipole in free space is known as 73 ohms.  Below a height of a half-wavelength, impedance is greatly affected by ground proximity.  At one wavelength and up, impedance begins to track the free-space value more closely.
A-007-007-010    7-7-10
Why can a horizontal antenna closer to ground be advantageous for close range communications on lower HF bands?
The ground tends to act as a reflector
Lower antenna noise temperature
Low radiation angle for closer distances
The radiation resistance is higher
> Near-Vertical Incidence Sky wave (NVIS) -- "The use of very low dipole antennas that radiate at very high elevation angles has become popular in emergency communications ("emcomm") systems.  This works at low frequencies (7 MHz and below) that are lower than the ionosphere's critical frequency -- the highest frequency for which a signal traveling vertically will be reflected." (ARRL Handbook, 2012 ed., 21.2.12 NVIS Antennas)
A-007-007-011    7-7-11
Which antenna system and operating frequency are most suitable for Near Vertical Incidence (NVIS) communications?
A horizontal antenna less than 1/4 wavelength above ground and a frequency below the current critical frequency
A horizontal antenna at a height of half a wavelength and an operating frequency at the optimum working frequency
A vertical antenna and a frequency below the maximum usable frequency
A vertical antenna and a frequency above the lowest usable frequency
> Near-Vertical Incidence Sky wave (NVIS) -- "The use of very low dipole antennas that radiate at very high elevation angles has become popular in emergency communications ("emcomm") systems.  This works at low frequencies (7 MHz and below) that are lower than the ionosphere's critical frequency -- the highest frequency for which a signal traveling vertically will be reflected." (ARRL Handbook, 2012 ed., 21.2.12 NVIS Antennas)
A-007-008-001    7-8-1
What is meant by the radiation resistance of an antenna?
The equivalent resistance that would dissipate the same amount of power as that radiated from an antenna
The resistance in the atmosphere that an antenna must overcome to be able to radiate a signal
The specific impedance of an antenna
The combined losses of the antenna elements and transmission line
> The power delivered to an antenna can be transformed in two ways:  some of it is lost through heat and dielectric losses, the rest is radiated.  The part that is radiated can be imagined to have "disappeared" into a virtual resistance.  Radiation Resistance is defined as an equivalent resistance that would have dissipated all the power radiated.  The dimensions of the radiating element, particularly its length, and its immediate environment, the proximity to ground for instance, affect radiation resistance.  Except for electrically short antennas, radiation resistance makes up most of the antenna impedance.  Antenna efficiency in percentage can be computed as Radiation Resistance over total resistance times 100.
A-007-008-002    7-8-2
Why would one need to know the radiation resistance of an antenna?
To match impedances for maximum power transfer
To measure the near-field radiation density from a transmitting antenna
To calculate the front-to-side ratio of the antenna
To calculate the front-to-back ratio of the antenna
> The power delivered to an antenna can be transformed in two ways:  some of it is lost through heat and dielectric losses, the rest is radiated.  The part that is radiated can be imagined to have "disappeared" into a virtual resistance.  Radiation Resistance is defined as an equivalent resistance that would have dissipated all the power radiated.  The dimensions of the radiating element, particularly its length, and its immediate environment, the proximity to ground for instance, affect radiation resistance.  Except for electrically short antennas, radiation resistance makes up most of the antenna impedance.  Antenna efficiency in percentage can be computed as Radiation Resistance over total resistance times 100.
A-007-008-003    7-8-3
What factors determine the radiation resistance of an antenna?
Antenna location with respect to nearby objects and the conductors length/diameter ratio
Transmission line length and antenna height
Sunspot activity and time of day
It is a physical constant and is the same for all antennas
> The power delivered to an antenna can be transformed in two ways:  some of it is lost through heat and dielectric losses, the rest is radiated.  The part that is radiated can be imagined to have "disappeared" into a virtual resistance.  Radiation Resistance is defined as an equivalent resistance that would have dissipated all the power radiated.  The dimensions of the radiating element, particularly its length, and its immediate environment, the proximity to ground for instance, affect radiation resistance.  Except for electrically short antennas, radiation resistance makes up most of the antenna impedance.  Antenna efficiency in percentage can be computed as Radiation Resistance over total resistance times 100.
A-007-008-004    7-8-4
What is the term for the ratio of the radiation resistance of an antenna to the total resistance of the system?
Antenna efficiency
Beamwidth
Effective Radiated Power
Radiation conversion loss
> The power delivered to an antenna can be transformed in two ways:  some of it is lost through heat and dielectric losses, the rest is radiated.  The part that is radiated can be imagined to have "disappeared" into a virtual resistance.  Radiation Resistance is defined as an equivalent resistance that would have dissipated all the power radiated.  The dimensions of the radiating element, particularly its length, and its immediate environment, the proximity to ground for instance, affect radiation resistance.  Except for electrically short antennas, radiation resistance makes up most of the antenna impedance.  Antenna efficiency in percentage can be computed as Radiation Resistance over total resistance times 100.
A-007-008-005    7-8-5
What is included in the total resistance of an antenna system?
Radiation resistance plus ohmic resistance
Radiation resistance plus transmission resistance
Transmission line resistance plus radiation resistance
Radiation resistance plus space impedance
> The power delivered to an antenna can be transformed in two ways:  some of it is lost through heat and dielectric losses, the rest is radiated.  The part that is radiated can be imagined to have "disappeared" into a virtual resistance.  Radiation Resistance is defined as an equivalent resistance that would have dissipated all the power radiated.  The dimensions of the radiating element, particularly its length, and its immediate environment, the proximity to ground for instance, affect radiation resistance.  Except for electrically short antennas, radiation resistance makes up most of the antenna impedance.  Antenna efficiency in percentage can be computed as Radiation Resistance over total resistance times 100.
A-007-008-006    7-8-6
How can the approximate beamwidth of a beam antenna be determined?
Note the two points where the signal strength is down 3 dB from the maximum signal point and compute the angular difference
Draw two imaginary lines through the ends of the elements and measure the angle between the lines
Measure the ratio of the signal strengths of the radiated power lobes from the front and side of the antenna
Measure the ratio of the signal strengths of the radiated power lobes from the front and rear of the antenna
> Beamwidth is defined as the width in degrees over which the major lobe is within 3 dB of maximum gain, this is equally described as the angle between the half-power points.
A-007-008-007    7-8-7
How is antenna percent efficiency calculated?
(radiation resistance / total resistance) x 100
(radiation resistance / transmission resistance) x 100
(total resistance / radiation resistance) x 100
(effective radiated power / transmitter output) x 100
> The power delivered to an antenna can be transformed in two ways:  some of it is lost through heat and dielectric losses, the rest is radiated.  The part that is radiated can be imagined to have "disappeared" into a virtual resistance.  Radiation Resistance is defined as an equivalent resistance that would have dissipated all the power radiated.  The dimensions of the radiating element, particularly its length, and its immediate environment, the proximity to ground for instance, affect radiation resistance.  Except for electrically short antennas, radiation resistance makes up most of the antenna impedance.  Antenna efficiency in percentage can be computed as Radiation Resistance over total resistance times 100.
A-007-008-008    7-8-8
What is the term used for an equivalent resistance which would dissipate the same amount of energy as that radiated from an antenna?
Radiation resistance
j factor
Antenna resistance
K factor
> The power delivered to an antenna can be transformed in two ways:  some of it is lost through heat and dielectric losses, the rest is radiated.  The part that is radiated can be imagined to have "disappeared" into a virtual resistance.  Radiation Resistance is defined as an equivalent resistance that would have dissipated all the power radiated.  The dimensions of the radiating element, particularly its length, and its immediate environment, the proximity to ground for instance, affect radiation resistance.  Except for electrically short antennas, radiation resistance makes up most of the antenna impedance.  Antenna efficiency in percentage can be computed as Radiation Resistance over total resistance times 100.
A-007-008-009    7-8-9
Antenna beamwidth is the angular distance between:
the points on the major lobe at the half-power points
the maximum lobe spread points on the major lobe
the 6 dB power points on the major lobe
the 3 dB power points on the first minor lobe
> Beamwidth is defined as the width in degrees over which the major lobe is within 3 dB of maximum gain, this is equally described as the angle between the half-power points.
A-007-008-010    7-8-10
If the ohmic resistance of a half-wave dipole is 2 ohms, and the radiation resistance is 72 ohms, what is the antenna efficiency?
97.3%
74%
72%
100%
> Antenna efficiency in percentage can be computed as Radiation Resistance over total resistance times 100.  In this example, 72 divided by 74 is 97.3%
A-007-008-011    7-8-11
If the ohmic resistance of a miniloop antenna is 2 milliohms and the radiation resistance is 50 milliohms, what is the antenna efficiency?
96.15%
52%
25%
50%
> Antenna efficiency in percentage can be computed as Radiation Resistance over total resistance times 100.  In this example, 50 divided by 52 is 96.2%

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{L13} Digital Signal Processing.

A-005-007-003    5-7-3
Which of the following functions is not included in a typical digital signal processor?
Aliasing amplifier
Analog to digital converter
Digital to analog converter
Mathematical transform
> Digital Signal Processing first transforms an analog signal to digital via an analog-to-digital converter (ADC), performs mathematical operations to filter or demodulate, for example, and recreates an analog signal through a digital-to-analog converter (DAC).  Aliasing is a situation where input frequencies above the sampling rate get erroneously reproduced as lower frequencies;  the situation is prevented through the use of an anti-aliasing filter (a low-pass filter).
A-005-007-004    5-7-4
How many bits are required to provide 256 discrete levels, or a ratio of 256:1?
8 bits
6 bits
16 bits
4 bits
> 256 levels in binary data spans the range 0 to 255.  Add the value of each bit in an 8-bit binary number, starting with the lowest:  1 + 2 + 4 + 8 + 16 + 32 + 64 + 128 = 255.
A-005-007-005    5-7-5
Adding one bit to the word length, is equivalent to adding ____ dB to the dynamic range of the digitizer:
6 dB
1 dB
4 dB
3 dB
> The number of bits determines the maximum number of distinct values available to represent a signal.  For each sample, the analog-to-digital converter selects the closest value to describe the instantaneous value of the input signal.  The difference between the real value and its numerical representation is a quantization error:  plus or minus half a bit, i.e., 1 bit total.  In digital terms, Signal-to-Noise Ratio and Dynamic Range are synonyms specifying the ratio between the largest possible sample value to the quantization error.  Dynamic Range for fixed-point processors can be approximated by the data word size:  6 dB times number of bits.  Each bit doubles the value, doubling voltage is 6 dB.
A-005-007-006    5-7-6
What do you call the circuit which employs an analog to digital converter, a mathematical transform, a digital to analog converter and a low pass filter?
Digital signal processor
Digital formatter
Mathematical transformer
Digital transformer
> Digital Signal Processing first transforms an analog signal to digital via an analog-to-digital converter (ADC), performs mathematical operations to filter or demodulate, for example, and recreates an analog signal through a digital-to-analog converter (DAC).  Aliasing is a situation where input frequencies above the sampling rate get erroneously reproduced as lower frequencies;  the situation is prevented through the use of an anti-aliasing filter (a low-pass filter).
