At 07:11 PM 12/7/2008, Jim Brown wrote:
>On Sun, 7 Dec 2008 11:56:36 -0800, Tree wrote:
>
> >This might not be the answer you are hoping for - but I think your
> >tower is too long electrically to work well on 160. I have never
> >heard of someone having a tower that high that really worked well.
>
>Don't tell K5RC (W7RN) that. His new 160 transmit antenna (about a
>year) is a quarter wave, and he is BIG on 160. When we were lined up
>trying to run JA this morning, one JA who was doing a lot of
>spotting said he was the loudest. Yes, the beam adds some top
>loading, but it should be possible to match that.
A little related experience, maybe. My tower is 97 feet, with two
tribanders and a shorty-forty on it, plus a 4-dipole lazy vee array for 80M
which is fed by feedlines that enter the tower at about the 40-foot level,
presumably coupling into the total picture. With advice from Earl, K6SE
(SK), I modeled the thing looking for a 50-ohm point on the tower. Tried a
couple of candidate locations, but the match with a simple series-cap shunt
feed was way off. Finally, I built an omega match with two transmitting
caps (no amp on 160), and got it matched in about a minute.
The good part - the antenna really works. With only 8-10 on-ground
radials, I feel pretty loud on 160. DX currently is about 80 countries,
strictly as a by-product of contesting (no serious top-band DXing) over the
last 3 winters.
About the only thing this proves is that for towers over an electrical
quarter wave, it's worth trying to feed it and see if it works.
73, Pete N4ZR
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