I'm assuming that the 40m elements are insulated or the boom would be much
longer than 1/2 wl on 20m. You could ground the elements, but you would
have to manipulate the antenna a little to do so. You didn't say how far
apart the antennas are, but it sounds like your TIC ring is very near the
top of the tower. Assuming that this is the case, you could connect an arm
from the TIC ring to the mast, replace the mast rotator with a lower bearing
and turn everything together using the TIC, unless you need the ability to
beam one direction on 20m and a different direction on 40m Or your could
mount the 40m beam to your mast and use the TIC further down the tower for
something else.
John KK9A
Subject: Re: [TowerTalk] Detuning booms?
From: Michael Dinkelman
Date: Sat, 18 Oct 2008 21:40:44 -0700
Hi Steve
I have 2 yagi's, a C31XR and a 3el 40M (old KLM) I just
refurbished and put up underneath it. As long as the two
booms are lined up. All is fine. (At least that makes it simple :>)
If they start pointing in different directions, the
20M SWR starts rising.
The 40M antenna's boom is about 30+'. I figure it's close
enough to 1/2 wave on 20M to make a difference. I might be
able to raise the C31XR a couple more feet on the mast - there
is about 8' between them now. I expect we'll try that first but
I don't expect it to make a difference. The 40M is on a
Tic Ring and isn't going anywhere for now (it took 3 months
to align the moon and the stars enough to get it on the tower :>).
So that'll make it hard to hang wires off the end. :>)
At least I have a work around for now - keep 'em lined up while
I'm on 20M. :>)
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