Helical Wound Antenna

I don't know yet exactly the number of winds and etc. Rich's post seemed a bit larger than needed... I found there's an FCC tech near me so I may pay him a visit and talk it over to see what his interpretation would be...

Basically-

3m of PVC pipe (2.5-3.5" in diameter)
1/4 wave worth of wire (24ga coated?) for your given frequency
Tuner (transmatch) -or- the appropriate coil
Shield was grounded x3 @ 16' deep each

I've not tried this for MW, this is basically what we used in the Army on some of our fixed HF installs. Though our pipe was a bit longer.

Somewhat like Rich's image we showed a large dB gain over the standard MilSpec doublet.

If anyone does try this please post up. I will follow up when I talk to the local FCC tech.

Somewhat like Rich's image we showed a large dB gain over the standard MilSpec doublet.

Just to note that my plots do not show large gain for the helical compared to the 5.15 dBi gain of a 1/4-wave monopole over a perfect ground plane.

In fact they show considerable reduction in gain relative to that monopole: about -17.5 dB for the helical radiator, and about -23 dB for the 3-meter linear radiator (1700 kHz).
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I meant based on the standard doublets we used in the Army the helical had more dB gain.

I meant based on the standard doublets we used in the Army the helical had more dB gain.

Here's a link that might be useful.

http://www.smeter.net/antennas/helix-2.php

I meant based on the standard doublets we used in the Army the helical had more dB gain.

Just curious... what is the peak gain in dBi of the "Mil Spec Standard Doublet" you refer to? If it is the intrinsic, peak, free-space gain of a 1/2-wave doublet, it should be 2.15 dBi.

Note that installing 1/2 of this radiator configuration as a monopole over/on a perfect ground plane, and with nearby 4/3 physical earth curvature produces close to 5.15 dBi peak gain, because all radiation is confined to one hemisphere.

Also note that such a configuration has MUCH more gain than the Part 15 helical monopole in the NEC calculations I posted.
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2 dBi sounds about right. Though this was 15 years ago so memory may be a bit weak 🙂

Thanks for the link!