On Mar 30, 5:58*pm, "Richard Fry" wrote:
If that helix occupies only about 90 degrees of a free-space wavelength,
then no matter how much linear wire length is contained in the coils of the
helix, that helical radiator will have the radiation resistance, pattern and
directivity characteristics of a 90-degree linear monopole of the same
end-to-end height.

I just modeled a 5.25' long helical using EZNEC at the 270 degree 3rd
harmonic frequency of 26.5 MHz. Both helical and whip are modeled as
lossless.

If I understand you correctly, the 270 degree helical should have a
TOA equal to a 5.25' whip. The TOAs differ by 6 degrees. The maximum
gain of the 5.25' whip is -0.25 dBi. The maximum gain of the 270
degree helical of the same length is +0.29 dBi, a difference of 0.54
dB.

The 5.25' whip is1/4WL resonant at 45.3 MHz with a maximum gain of
-0.25 dBi at a TOA of 27 degrees. The 5.25' helical at 45.3 MHz has a
gain of -3.13 dBi at a TOA of 24 degrees, a difference of 2.88 dBi and
3 degrees.
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73, Cecil, w5dxp.com