[TowerTalk] Looking for a Short Rotatable Dipole or...

[Kevin Stover]

K9YC has given the best advice.

A dipole, any dipole at less than 1/2 wavelength isn't going to have any 
lobes to rotate so scratch the dipole idea. It'll be pretty much 
omnidirectional.

Elevated vertical with elevated radials is the way to go. The radials 
need to be 1/4 wavelength at the resonant frequency. I would put up a 
minimum of two and had four per band on my roof mounted Hustler 6BTV. 
The 40 and 80m radials were anything but straight. All of the radials 
came off the bottom of the vertical at about a 30 degree angle.

I tuned the vertical for the part of the band I wanted, then tuned two 
radials at a time, making a dipole out of them and cutting them to match 
the vertical resonant frequency. No big deal, works like a charm.


On 4/28/2016 12:09 PM, Jim Brown wrote:
> On Wed,4/27/2016 11:31 AM, Eric Rosenberg wrote:
>> I''m looking for a 40m rotatable dipole (preferably a F12 EF-140S) to 
>> add to the C3-SS on my roof.
>
> Eric,
>
> How about a vertical on your roof with radials? Both could be wire. 
> The vertical wire could be mounted to a fiberglass mast like this. 
> http://www.qsl.net/dk9sq/ Or do telescoping Al tubing and guy it at 
> the top.
>
> The radials don't need to be perfectly at right angles, and you don't 
> necessarily need four -- three would work pretty well. Mounting it on 
> the roof greatly reduces ground losses and improves the vertical 
> radiation pattern. See my modeling study of this that ran in NCJ last 
> year.
>
> http://k9yc.com/AntennaPlanning.pdf
>
> 73, Jim K9YC
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-- 
R. Kevin Stover
AC0H
ARRL
FISTS #11993
SKCC #215
NAQCC #3441


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