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TopBand: 160 ant/ 80 elev feed

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Subject: TopBand: 160 ant/ 80 elev feed
From: N5JA@contesting.com (Jon Barclay N5JA)
Date: Thu, 28 Nov 1996 10:34:30 +0000
Harold Smith wrote:
> I think that an elevated feed for 80 would work fine but mess up the 160
> operation. Maybe someone has tried it ?
> 
> 73 de Price W0RI

I usually keep my mouth (fingers?) shut to protect the visibility of my
ignorance, but, what the heck...  the subject seems to have hung around
for a while...

I have a 135' tower with stuff on top including a KLM 20M6 antenna that
has insulated elements, plus some VHF stuff sticking up above it all.
Altogether, the boom of the 20M6 plus the VHF stuff basically forms an
upside-down "T" sitting atop the tower, with each leg of the "T" being
about 30' long.  I shunt-feed the whole mess with a gamma feed up to the
95' point for 160M, no need for an omega-match there.

Year before last, I put four 66' downward-sloping radials from about the
75'-point (dictated by where I could clear the other antennas that are
side-mounted on the tower).  I had to insulate the radials from the
tower to keep them from totally messing up the 160M performance, and
used a small vacuum relay to connect the radials to the tower for use on
80M.  I added a gamma feed for 80M from that 75' mark up to some point
where I got a reasonable match (I forget exactly how high it attached).

In the end, it seemed to work about as well as the slopers that I had
been using, but not miraculously better or anything, and I had to climb
the tower to tune it since I didn't have anything remote on the gamma
capacitor.  So, it can work, and maybe I'll build a nice remote-tunable
matching box one day and re-install it.  Or, maybe, I'll just build that
4-square...

Anyway, I'm sure more radials would've worked better, etc., so there's
room for improvement.  My 2 cents if anyone's interested.

-- 
Jon A. Barclay  N5JA  (ex-AA5BL)
N5JA@contesting.com

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