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.
John KK9A / P40A
To: "TowerTalk@contesting.com" <TowerTalk@contesting.com>
Subject: [TowerTalk] Resonant boom
From: Stan Stockton <firstname.lastname@example.org>
Date: Sat, 23 Oct 2010 20:04:03 -0500
Anyone by chance have an easier to accomplish idea other than one I
remember being suggested to someone else with a similar problem -
fishing a wire through a hole near the center of the boom and letting
it hang out the end. I can watch the SWR on my 40 meter antenna go
from 1.2/1 to 2.0/1 just by turning the rotatable 40m Yagi or the 20m
Yagi which is about 175 feet away and 65 feet lower. Boom is 65 feet
and elements are insulated.
Lesson learned on boom lengths...
I would prefer to fix it with the least amount of work. I can
probably do the wire thing on one side but not the other due to an
weight-balance obstruction. Hate to have about 15 feet of wire
hanging out if the back of the boom.
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