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Re: Topband: Snow plus vertical

Subject: Re: Topband: Snow plus vertical
From: K4SAV <>
Date: Thu, 28 Feb 2008 09:21:20 -0600
List-post: <">>
WY7I wrote:

>Hi Topbanders,
>Here's something that's bugging me, and perhaps a few of you fellow snow-cats 
>can give me some advice. 
>I'm considering a triangle of MA160V's (Cushcraft) along with radial plates on 
>each. The problem is that here in Southern Colorado, we receive about 4-8 feet 
>of snow during the winter. It seems obvious that I can't ground mount the hot 
>side of the vertical because it will get covered up. SO, I'm going to raise it 
>up by mounting it on top of a steel tube that runs down into the radial plate. 
>It would look sort of like an umbrella stand for your outside patio umbrella.
>I'm not familiar with this antenna yet, but--what will happen if I raise the 
>feed point up? I'm thinking that the 7' tube, being connected to the radial 
>system will work as normal. Will the elevated feed point affect the impedance?
>Any comments on this idea? 
>Regards to all,
The extra length at the bottom, between the feedpoint and the radials, 
will look like part of the antenna.  It will move the resonant frequency 
slightly and the feedpoint impedance a little.  It's like an off 
center-fed dipole, except here it is a vertical and the feedpoint is 
tapped higher up on the antenna.  It will also create some feedline 
common mode currents unless the feedline shield is again tied at the 
point where the radials are attached.  It should work OK.

Jerry, K4SAV
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