Hi Grant and Todd
I suggest there is also potential for a 4th problem - mutual coupling
between the vertical wire and supporting tree. Any such coupling would be
smaller for the 43 ft vertical if it was located further away from the tree.
It would be interesting to see if there is any noticeable change in the SWR
curve and performance by increasing the distance between the vertical wire
and tree trunk. But I also appreciate that space and other factors may
preclude Todd from doing this.
73, Brian VK3MI
Message: 11
Date: Sat, 29 Dec 2018 09:00:03 -0800
From: Grant Saviers <grants2@pacbell.net>
To: Todd Goins <tgoins@gmail.com>, TopBand List
<topband@contesting.com>
Subject: Re: Topband: Inverted L improvement question - Part 2
Message-ID: <afe940ac-e4cd-286e-fb33-c801eae88804@pacbell.net>
Content-Type: text/plain; charset=utf-8; format=flowed
Problem #1. The swr indicates about a 140Khz plus < 2:1 bandwidth (2 *
1880-1810) which implies a high radial resistance. Are the elevated
radials fully insulated from trees, not contacting foliage, etc? Add
three more.
Problem #2. Your coiled coax choke may be making things worse. Check
out the just released designs from K9YC and build one. 17 turns RG400
on one FT240-31.
Problem #3. The increased gain of the T may be causing BCB desense of
the 7300. You need a BCB filter. Also the poor choke may be letting a
lot of common mode noise into the antenna.
Grant KZ1W
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