Stan, you just have too many long boom antennas!
It should not be that difficult to model the system and then you can
experiment and see how to fix the problem. The 20m beam at 70' with nothing
below it should not be that difficult to take down, adjust and reinstall.
Can the boom be electrically shortened by using fiberglass on the ends to
support the outer elements?
To: "TexasRF@aol.com" <TexasRF@aol.com>
Subject: Re: [TowerTalk] Resonant boom
From: Stan Stockton <email@example.com>
Date: Sun, 24 Oct 2010 10:58:19 -0500
Installing dummy elements out as far as I could reach was what I was
going to try first but dont know whether the would be far enough out
to do the trick. Yesterday I looked to see where the nearest element
is and it is probably out of reach. I may try tuning the thing and if
no luck put up another tower (temporarily or not) 30 feet to Northwest
of it, rotate the antenna to extend the boom on either end, and then
(if permanent) take a section off the new tower and put up an H frame
of 10m antennas fixed on Europe using both towers.
Not sure I even want to know the real impact of this resonance on the
pattern of the 40. I can say that I haven't had the "feeling" that
the 40m antenna has worked as well as it did a few years ago.
Unfortunately, about 75% of the time the 20 needs to be pointed in a
direction that makes it the worst.
Thanks to you and others for the thoughtful suggestions. I'll report
what I end up eventually doing.
Sent from Stan's IPhone
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