Date: Mon, 14 Oct 1996 20:32:37 -0400 (EDT)
From: Frank Donovan <email@example.com>
To: Tony Wanschura <firstname.lastname@example.org>
Subject: Re: 40-2CD proximity to 20-4CD
I suspect the entire structure of your your 20-4CD antenna (boom plus
uninsulated elements) has a nice 40 meter resonance! Twenty years ago
I had a similar experience with a 40 meter full size three element beam.
When I installed a three element 20M beam 10 feet above the 40M beam, the
40M beam became omnidirectional and the VSWR was 3:1 ! My solution was to
insulate the elements of the three element 20M beam from the supporting
boom and the problem totally vanished!
I doubt that five additional feet of separation will do much good, that is
only .035 wavelengths of additional separation... Fifty feet of
additional spacing would do the trick tho... Fooling around with only
the driven element or antenna switch isn't likely to do much either,
because the problem is systemic, affecting the entire antenna rather than
just the driven element!
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