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Re: Topband: electrically shortening a tall grounded tower

To: Bob Kupps <n6bk@yahoo.com>
Subject: Re: Topband: electrically shortening a tall grounded tower
From: Herbert Schoenbohm <herbs@vitelcom.net>
Reply-to: herbs@vitelcom.net
Date: Sat, 26 Sep 2009 08:34:47 -0400
List-post: <topband@contesting.com">mailto:topband@contesting.com>
Bob Kupps wrote:
> Hi
> Is there any effective way to electrically shorten a tall grounded tower to 
> 1/4 wave? I tried modeling a 1/4 wave cage surrounding the tower but it still 
> shows a lot of current in the protruding section with resulting high angle 
> radiation. Then I tried modeling a 1/4 wave stub above the cage grounded at 
> the top to the central tower which appeared to turn it into a dipole and 
> still significant current above the stub. I was also thinking of using an 
> external parallel resonant trap/choke but would this actually work when 
> situated at a zero current point at the far end of a 1/4 wave monopole?
> Thanks and 73 Bob N6BK/HS0ZIA
>
>
> Bob,

You might consider feeding it with a shunt fed cage at about 1/4 down 
from the top and attach elevated 1/4 wave radials at that point.  I had 
a 308 foot tower and took the easy way out by running up a halyard and 
hanging slopers or a delta loop.

Cheers,

Herb, KV4FZA
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