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Re: Topband: Adding radials, a question

To: <>
Subject: Re: Topband: Adding radials, a question
From: "Tom Rauch" <>
Reply-to: Tom Rauch <>
Date: Thu, 2 Sep 2004 09:22:38 -0400
List-post: <>
Watch the sensitivity of the analyzer to external voltages!

Even without that problem, there are other problems. Long
ago when looking at elevated radials and mobile antenna base
impedance, I concluded I could have widely varying feed
impedances and bandwidth that doesn't necessarily track with

By using short radials and loading them with loading coils,
I could create a very low feed resistance and yet have very
high ground loss. By moving capacitance down low on an
antenna I could also have a very low feed resistance while
decreasing field strength.
My most efficient mobile antennas have the widest bandwidth,
and I can change the resonant frequency and base impedance
significantly by adding one ground strap to my pickup truck
between the cab and the bed, yet FS hardly changes at all.

If my goal was a low feed resistance, I could accomplish it
with terrible efficiency and very narrow bandwidth for
either fixed or mobile antennas.

Indirect measurements should always be the last possible
resort, and verified through some other method.

73 Tom

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