I was not suggesting to insulate the boom from the mast. My suggestion was
to install insulating sections on the boom so you electrically have two or
three boom sections or perhaps to use fiberglass boom material for the end
elements and a shorter aluminum boom in the center.
To: <towertalk@contesting.com>
Subject: [TowerTalk] Resonant boom
From: "Jim Thomson" <jim.thom@telus.net>
Date: Sun, 24 Oct 2010 19:22:10 -0700
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Insulating his 65' boom from the tower will accomplish nothing. What's to
be
avoided is floating 1/2 waves.....and grnded 1/4 waves. Right now, his
65'
boom consists
of 2 x grounded 1/4 waves.... back to back. You only need ONE 1/4 wave
grnded portion
to screw up a 40m ant...and he has 2 of em. See my previous post. His
boom
will have to be
de-tuned by one of the methods that folks have described.
Date: Sun, 24 Oct 2010 11:03:25 -0400
From: <john@kk9a.com>
Subject: Re: [TowerTalk] Resonant boom
That interaction is incredible since the beams are 186' apart. I don't
recall my 60' boom yagis causing a 40m problem at my previous QTH with 20'
spacing and I'm not sure yet if it's a problem at my new home with 75'
spacing since the 40m beams are not yet connected. I have modeled adding
other antennas to my tower and saw boom interaction. I considered
insulating the boom, but I have not tried this method. Certainly grounding
the reflector and last element would change the boom resonance, but not sure
how feasible that is since the 20m beam is installed or if it would help. A
temporary fix is to use Green Heron controllers and link the two antennas
together to ensure that they are pointing in the same direction when on 40m.
GL
John KK9A / P40A
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