We all don't have unlimited budgets and space so we make compromises.
Actually all antenna systems have compromises. I have homebrew 15m beams
<20 feet above and below my lower 40m OptiBeam. I see no SWR change when
rotating and little pattern change on my model. I have a couple of U.S
contest single band records on 40m and one on 15m, so it works to at least
some degree. The OptiBeam is not resonant on 15m. Personally I would not
use an antenna that was if it had to be on the same tower.
John KK9A
To: <towertalk@contesting.com>
Subject: Re: [TowerTalk] Modeling question - for the experts!
From: "Ed Sawyer" <sawyered@earthlink.net>
Reply-to: sawyered@earthlink.net
Date: Thu, 2 Jun 2016 13:48:19 -0400
I believe that K3NA did some nice work on this subject that was published a
few years back in NCJ. I don't remember the details, but I remember
concluding that you don't want your 40M beam and your 15 M beams on the same
tower if you can help it (mine are separated by 140 ft). Also, that there
are lots of pattern distorting interactions on multiple yagis stacked on a
tower. I have 4/4 on 20M with a 3 el in between facing south. I am sure
that is not what I want to be doing and have though about removing it and
doing something else for 20M south.
Ed N1UR
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