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RAC

by Ralph Cameron VE3BBM

RAC Logo Introduction and Background
RAC Logo Who is Affected?
RAC Logo Why do the Effects Occur?
RAC Logo What do you do?
RAC Logo What are EMC standards?
RAC Logo Frequently Asked Questions

Introduction and Background

Electromagnetic compatibility (EMC) is a general term describing how well electronic equipment behaves technically, when placed in close proximity to each other. It's somewhat like social compatibility and can generate social friction as well as technical problems. The resolution of such problems, without exception, requires cooperation between the affected parties. It is a technical "nuisance" governed by the Laws of Physics.

P>Lack of EMC causes malfunction which must be addressed to restore the intended or designed function of the affected equipment/system. EMCAB-1 described some of the equipment which 15 years ago had impaired or degraded function, impaired audio or visual effects from being classed as Radio Sensitive Equipment (RSE).  Ever increasing spectrum usage means being aware that more problems will occur and why and what you can realistically do about it.

Who is affected?

Amateur operation usually takes place in built up areas where lot sizes determine the extent of antenna installations. Close proximity is the greatest contributor to these problems with an obvious effect on neighbours.

EMC problems can extend to great distances when electrical/electronic equipment malfunctions and produces undesired signals in those frequency channels assigned for specific purposes. There are thousands of examples, all due to lack of compatibility.

Why do the effects occur?

The effects can occur intentionally or unintentionally. Intentional effects are deliberate i.e. jamming. They may also occur due to misadjusted equipment or with equipment which ignores current spectrum usage allocations Frequently, it appears to be a lack of awareness that creates the problem. 

One serious problem facing the Canadian radio amateur is the fact that incidence of occurrence is no longer recorded. This creates a barrier to addressing and resolving the problem because: 

a) Dealers have not supported/warranted equipment from such effects (see RIC-17).

b) Consumers know even less about the effects and have been placed in the situation of having to resolve something they know little about. They rely on their dealer and failing that, often rebel and refuse to cooperate.

c) Observations over the past 20 years, indicates HF operation (1.8-30Mhz) accounts for 95% of Electro Magnetic Interference (EMI) problems. Digital technology resolved few problems.

d) First hand experience has shown that almost 95% of the visual and audible effects noted above can be removed by suitable common mode choke, i.e reduce the conducted component as well as the radiated component creating the effect.

e) One encouraging study performed by the Radio Advisory Board of Canada provided agreement that lack of awareness was the number one weakness in finding solutions. An agreed methodology of Repair, Replace or Refund never happened; although, some companies adopted the policy (see RIC-17). 
A less costly approach is to include such devices at the product design stage, where again costs are minimal compared to resolving after sale.

f) An interim approach, EMCAB-2, sought to limit transmitter field strengths to design limits which suppliers to the European consumer electronics market had to meet. While increasing antenna separation from a neighbor can help reduce the undesired effects, there is no control over how long or how much wire is attached to the neighbor's equipment. The technical solution should appear obvious and that would be to isolate, as much as possible, the combined antenna effects i.e. from the amateur and from the consumer (see d) above).

What do you do?

After reading the foregoing, one can appreciate the potential for failure in convincing a neighbour (sometimes a total stranger) of what is happening.

1. A general approach that often works requires improving the isolation between the undesired signal and the consumer equipment so that the effects can be tolerated or eliminated. What may appear as a 95% solution to your neighbour, may also be acceptable to him or her. One approach is seldom 100 % successful and depends on the coupling previously described. Why worry that the calculated field strength for a given power and antenna system will be 4.6V/m when using EMCAB-2 as a criterion when you can actually remove the offending signal to the point where the equipment can tolerate it and the neighbour is happy.

2. Read up on the subject : Industry Canada want you to enjoy your form of entertainment as much as your neighbour's so become familiar with potential problems and try to understand why the effects occur. The client procedure circular CPC 3-14-01, Determinations of Harmful Interference with respect to Radio-Sensitive Equipment is must reading. It is published by Industry Canada and is an excellent ice breaker to hand to cooperative consumers. Beware of solutions that requires devices to be installed inside a consumer appliance. Such intrusion may negate the electrical safety certified by CSA, unless performed with a consumer release which is to be highly discouraged.

What are EMC standards?

EMC standards are designed to ensure that items of electronic equipment do not cause problems to each others operation or, worse still, give rise to malfunctioning of the equipment. Such standards prescribe the technical performance for equipment to deal with various EMC phenomenon.

Numerous EMC standards have been developed in several standards making forums. The principal standards organisations developing EMC standards  are:

International Electrotechnical Commission (IEC)

The IEC is the world organisation that prepares international standards for electrical, electronic and related technologies, including EMC matters. The IEC is based in Geneva, Switzerland and Canada participates in this organisation.

International Special Committee on Radio Interference (CISPR)

CISPR is a special committee that operates under the IEC. This committee is essentially responsible for making standards for the protection from interference to radio and television broadcasting reception. CISPR is based in Geneva, Switzerland and Canada participates in this organisation.

European Committee for Electrotechnical Standardization (CENELEC)

CENELEC is the European standards making body on electrical and electronic related matters. In developing standards on EMC, it is the policy of CENELEC to adopt, where possible, IEC or CISPR standards. CENELEC has responsibility for developing harmonised standards for use in the European Union. European harmonised standards are also known as Euro Norm (EN) standards.

The Canadian Standards Association (CSA)

CSA is the standards making body in this country.  A number of EMC standards have been published by CSA.

 

(to be continued....)

EMI= Electromagnetic Interference
RFI= Radio Frequency Interference


EMC and Frequently Asked Questions

Q. - How does one cope with touch lamps that are affected by RF, when I'm on the air?

A. - The touch lamps make use of body capacity so that as a hand is moved near the lamp an electronic circuit causes the lamp to switch from Off to Dim, Medium or full brilliance. They have virtually no rejection of RF and depending on the sensitivity, may trigger with very small amounts of local RF.

They are particularly bothersome because they are usually used on bedside tables and the only temporary cure is to disconnect them.

VE6FN, Ben Kendall, of Calgary, AB has kindly provided a couple of approaches that he developed. Both remedies cure the problem. Be aware that some skill with a soldering iron and tools is required and that the person installing the "fix" be knowledgeable and get permission from the owner before proceeding. The following links are images of typed pages and are a bit slow to download.

Page 1
Page 2
Page 3

Q. - I can hear noises in my amateur receiver whenever I turn on my TV set. Is this an EMC problem?

A. - Yes, compatibility requires suppression of effects (within reason) of devices which generate undesired signals during reception or transmission. Within the same home, the harmonics of the TV high voltage power supply can be sufficiently strong to cause objectionable interference to amateur reception.

Occasionally, reports are received from VHF operators of unstable unmodulated carriers. These often turn out to be oscillating TV mast mounted preamps. Electronics doesn't last forever and as components age, bypasses no longer perform their purpose and cause such malfunction.

Q. - How can I calculate my field strength in order to approximate compliance with EMCAB-2?

A. - There is a really neat website at http://n5xu.ae.utexas.edu/rfsafety which will enable you to calculate approximate field strength by inserting the numbers. N5XU has developed a formula for use in determining compliance with the mandatory U.S. radiated field limits for health concerns. This very useful website can be used for similar calculations for ensuring compliance with Canada's Safety Code 6 concerns. (If you are interested in more detail about safety compliance, you should also visit the RF Safety page on the RAC web site).

To Be Continued


If you would like to send Ralph a question regarding EMC, you can enter your Name, Callsign and RAC member number (from your TCA label) below and you will receive a personal answer.

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Thanks  
Ralph Cameron VE3BBM

 


Here are some links to web sites with more in depth information.

Canadian RF Immunity Information

RAC Logo EMCAB-1 Immunity of Electrical-Electronic Equipment 
RAC Logo EMCAB-2 - Criteria for Resolution of Immunity Complaints 
RAC Logo RIC-17 - Electromagnetic Immunity (Radio Sensitive Equipment)
RAC Logo NIR - Guidelines for the Measurement of Radio Frequency Fields from 3 kHz to 300 GHz
RAC Logo Determinations of Harmful Interference with respect to Radio-Sensitive Equipment (CPC 3-14-01)
RAC Logo CSA C108.9
RAC Logo CSA EMC standards

USA RF Immunity Information

RAC Logo FCC note on RF immunity testing
RAC Logo Frankonia EMV Field Meter, EMI, RF, immunity, susceptibility, emission, test, measurement, reference, MPR, TCO, radiated, FMS
RAC Logo ARRLWeb General Information about RFI-EMI
RAC Logo Links to EMC Web Sites

European RF Immunity Information

RAC Logo CISPR 22 Radiated and Conducted EMI Limits

Other Useful Links

RAC Logo Industry Canada Amateur Radio Service Centre
RAC Logo (RIC-66) - Addresses and Telephone Numbers of Regional and District Offices
RAC Logo RR - Radiocommunication Regulations