Topband: electrically shortening a tall grounded tower

Bob Kupps n6bk at
Fri Sep 25 22:10:47 PDT 2009

EZNEC 5. Regardless of my inability to model I would be interested in any practical solutions that have already been tried and known to work.
Thanks 73Bob 

--- On Sat, 9/26/09, W2XJ <w2xj at> wrote:

From: W2XJ <w2xj at>
Subject: Re: Topband: electrically shortening a tall grounded tower
To: "Bob Kupps" <n6bk at>, "topband" <topband at>
Date: Saturday, September 26, 2009, 11:56 AM

What software are you using? Often modeling software can not handle cages.

On 9/25/09 11:50 PM, "Bob Kupps" <n6bk at> 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
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