To: <topband@contesting.com>
> Date: Wed, 24 Jun 1998 22:00:28 +1000
> From: P & V Nesbit <pnesbit@melbpc.org.au>
> Subject: TopBand: Re: Measuring impedances through a filter
> To: topband@contesting.com
Hi Peter,
> Quite true, however this problem is easily resolved. Assuming the filter is
> home brew, feed the component values into an analysis program like ARRL
> Radio Designer, and try different terminations at the output end until you
> get the same impedance at the input end as what you measured. The
> termination at the output end will then be the same as the actual
> terminating impedance.
Maybe not, it depends on the filters loss, numb4er of sections, slope
of the filter, and component tolerences. I don't want to "go there"
on the topband reflector because it would take a good sized page to
cover all the theory.
Results could be pretty far off in some cases, especially when a
multi-section filter will small cheap components is used close to its
cutoff frequency.
If this method is used, be SURE to verify the results with a dummy
load of the same impedance you calculate for the antenna.
73, Tom W8JI
w8ji.tom@MCIONE.com
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