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Re: Topband: Adding radials, a question

To: "Richard Detweiler" <>
Subject: Re: Topband: Adding radials, a question
From: "Tom Rauch" <>
Reply-to: Tom Rauch <>
Date: Fri, 3 Sep 2004 01:14:49 -0400
List-post: <>
> I respectfully disagree with your comment.  Others may be
able to confirm
> seeing the Q rising as radials are increased along with
other points being
> made.

Hi Richard,

I don't think the article you mentioned is correct.

If I have one elevated radial and increase the number to
ten, bandwidth of the antenna will increase quite a bit. At
the same time, efficiency will increase. If I have long
radials and replace them with short radials and retune the
antenna, efficiency will drop even though bandwidth became

As another example, I was measuring a "no ground radials"
vertical. I added a large ground and efficiency increased
several dB while the bandwidth became almost three times

In resonant systems, neither bandwidth nor base impedance
track efficiency except in very specific situations. If it
doesn't track all the time, it isn't a good method of
determining efficiency changes. In many cases, wider
bandwidth actually occurs along with increased efficiency.

I think you mentioned something about the link claiming
radiation resistance increases as we add radials. Radiation
resistance is set by the height and current distribution in
the vertical, not changes in the non-radiating part of the

There also was a claim radials only need to be about as long
as the antenna. That's not quite true either. The shorter
the antenna the more important it is to have a large number
of long radials.

73 Tom

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