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Re: Topband: Shunt Fed Question

To:, TopBand List <>
Subject: Re: Topband: Shunt Fed Question
From: Art <>
Date: Sun, 07 Dec 2008 18:01:43 -0700
List-post: <">>
Brian Sarkisian, KG8CO wrote:
> I have 125 ft of Rohn 45 with a 4 element KLM 40 meter beam on top.
> 1. At what height would you attach the top of the gamma match?
> 2. How far away would you place the gamma match away from the tower.
> The tower currently has 120 100ft radials connected to it.
> Thank You
> Brian, KG8CO

My 160 ant for 16 years til 2004 was a 160 ft R45 tower with 15 ft mast 
and several antennas. At the top was a 52 ft boom homebrew 20. It worked 
gangbusters on 160. However. It was fed at 32 ft AGL as a ground plane. 
The feed wire was attached at 90 ft AGL spaced 3 ft from a tower leg. 
All empircal, all based on junkbox availability. According to ON4UN's 
book using his best guess formula it was about equivalent to 5/8 wave. 
In the day I did not have a Z meter. I just matched for lowest SWR at 
1830. The match was narrow which, from the literature, I took to mean 
the ground losses were relatively low - performance seemed to bear that out.

Good luck with your setup.

73 Art
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