On 4/24/2011 10:52 PM, Jim Brown wrote:
> On 4/24/2011 4:21 PM, Rick Karlquist wrote:
>> It is difficult to feed a vertical dipole in the traditional
>> way in the center without the feedline affecting the pattern.
> Rudy Severns, N6LF, figured out a way to end feed it, and I expanded on
> it. I built my version and hung it from a pulley high in a redwood,
> with the top about 110 ft above ground. It works, but when I compared it
> to my horizontal dipoles, the dipoles were ALWAYS a couple of S-units
> stronger.
It shouldn't have been except for relatively close in stations. (IOW
state side) The half wave vertical, end fed has a very low angle of
radiation and acceptance. I would expect it, like all the real
verticals I've used to normally excel on long haul and be pretty
miserable on short or stateside contacts. I found them to be good at
reducing state side QRM making it easier to copy the DX. Unfortunately
the only half waves I've played with were on 40 (1/4 wave on 75) I
never managed to get them in the phased array, although I did the
quarter waves.
> Before I built it and hung it in the tree I also modeled it in
> NEC.
>
Seems to me the handbook had a good method for feeding a half wave vertical.
IIRC it was much like a tuned auto transformer. Little in the way of
radials was needed. I think the same feed was used on the bob tailed
curtain.
73
Roger (K8RI)
> See my power point on Coax Chokes for photos and details of my feeding
> method and printouts of the modeling results. On the air comparisons
> correlate quite well with the model predictions.
>
> 73, Jim K9YC
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