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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