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Re: [TowerTalk] Tower resonance measurements

To: "Rudy Severns" <>
Subject: Re: [TowerTalk] Tower resonance measurements
From: "Rick Karlquist" <>
Date: Wed, 25 Feb 2009 10:07:17 -0800 (PST)
List-post: <">>
Rudy Severns wrote:
> Hi Joe,
> To measure tower resonances, all I'm doing is measuring the series
> impedance
> of the sensing loop while it is attached to the tower.
> Without the tower the loop is just an inductor up to the point where the
> loop length approaches 1/4-wave resonance where it starts acting as a two
> wire shorted transmission line.  The coupling to the tower is very loose
> so
> when you go past a tower resonance all you see is a small bump in the
> impedance.  In fact the deviation in |Z| (magnitude) is almost too small
> to
> see, that's why I use the phase of Z.  the deviation in phase is much
> easier
> to see but it is still quite small.  That's why I use a VNA for the
> measurements.

Maybe I am missing something here, but this seems to be
basically like the old grid dip oscillator techique, only
you would monitor the frequency of the oscillator instead
of the grid current.

Rick N6RK


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