I made one of those (still have it, but in storage)...
I used 4 elevated radials and had them sloped downward at 30 degrees from
horizontal, and the feedpoint about 20 feet high.
SWR at feedpoint was 1:1 perfect at 7100 KHz, maybe 1.2 at the edges of the
band.
The angle of the radials can be used to adjust the impedance. Horizontal gives
about 35 ohms, maybe 1.4 SWR.
73, Merry Christmas... Terry / W1TR
Message: 4
Date: Thu, 22 Dec 2011 14:23:56 -0800
From: "Tom Osborne" <w7why@frontier.com>
Subject: [TowerTalk] Elevated vertical
To: "Towertalk" <towertalk@contesting.com>
Message-ID: <443EA86127FB413BA9720F4D38FF7AE3@Tom>
Hi All
I just put up an elevated 40 meter vertical. The feedpoint is around 15 feet
or so up and I have 8 radials on it right now. I cut the radials the same
length of the vertical section. I have a coil of around 8 turns of coax for a
choke.
It works good, as the first day I put it up, I worked some Europeans from here
in Oregon.
The thing that seems strange is that at the low end of 40, the SWR is around
1.3:1. As I go up the band, it goes up to about 1.5:1, then when I get to the
top of the band, it goes back down to 1.2:1.
Is that because some of the radials are resonating at different parts of the
band?? 73
Tom W7WHY
73, Terry / W1TR ☺
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