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[TowerTalk] Taming an 80 m beam

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Subject: [TowerTalk] Taming an 80 m beam
From: (Steve)
Date: Thu, 26 Jul 2001 23:20:36 +0100
Hi Chris, your post is interesting reading and I can sympathize with
your experience with tuning or should I say taming the Force 12 antenna.
I had a similar experience with a C31XR where I had to put it up and
down tower a few times. I have it up at 100 ft so its no small task. The
Cushcraft XM520 at 150 ft. went up and tuned up good. I wish Force 12
had better instructions on how to tune the antenna and for what portion
of the band you want it to play in. I had to reduce the 15m driven
elements by 1.25 " to get the low swr point into the 15m band. I suppose
I could have shortened it a bit more since the low swr point is at
21.050 mc. now. A friend had a similar experience with a 12 & 17 dual
bander where the low swr point was 1.5:1 on 17m and 1.7:1 on 12m and
everyone I talked to that put up C31XRs had high swr on 15m. The XT34
that I've had for over 20 years has better swr curves than the Force 12
and the KLM was designed before computer modeling was main stream. It
just make me wonder how much loss that 100 ft. peice of coax has that is
used to check the antennas at the factory.

  ps as a side note yes I tried ever combination of wire and coil
spacing before I shortened the 15m element

gl es 73 cu in the contests. Steve

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