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Helix Design Calculator

Helix Design calculator by VE3KL.  Can be used on-line without downloading to your computer

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A simple 50-ohm match for 70cm Helix antennas

TCAHotlink: 1996 Article by Clare Fowler,VE3NPC

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Helical Antennas, Theory and Practice

Design and Theory discussed with the Kraus and Emerson formula compared

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L.B. Cebik: Axial model Helix Design notes

Detailed design notes on Helix Antennas

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Geometry of the Helix

Basic Math of the Helix structure

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Figure 1  PDF

Helix Antenna Drawing.  The Helix is described by the following parameters: the overall length, L, the spacing, S, between turns, the diameter, D,   and the width, W, of the ground plane. Another parameter often referred to in the literature is the pitch angle which is related to S and D.

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Figure 2  PDF

Helix Gain. Vs. Length.  This graph shows the gain of the Helix antenna using the Kraus and the Emerson models as well as the experimental results from King and Wong.  The parameters for the Kraus model are very similar to the Emerson model. The Circumference for the Kraus model is 1.0 wavelengths and the Spacing between turns is 0.22 wavelengths while the Circumference, Diameter and Pitch angle for the Emerson model vary with the length of the Helix.

Notice that the experiments by King and Wong fall between the two theories.

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Figure 3  PDF

Photograph of the 70 cm antenna designed and built by Clare, VE3NPC. Notice that the boom is fabricated from thin fibre-glass fencing material and not metal.  We believe that this material is better than either metal or thick PVC piping material. The losses in PVC at UHF frequencies are not well documented. Also, the induced current in a metal boom can produce extra losses if there are any irregularities in the construction of the Helix.

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Figure 4  PDF

Close up photograph of the back of the antenna near the connector and matching structure.  Since the impedance of the Helix is approximately 230 Ohms, a quarter wave parallel plate transformer of characteristic impedance equal to107 Ohms is used for a 50 Ohm system. The characteristic impedance of the transformer used in this design is variable. Notice that the circular length of the transformer is equal to one quarter of a turn (one quarter of a wavelength).

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