>Rich Measures wrote:
>>Using a Hewlett-Packard Model 4191A RF Impedance Analyzer, Wes measured
>>from 49 ohms to 169 ohms of Rp -- depending on test frequency for the two
>>types of suppressors, both of which used a suppressor R of c. 100-ohms.
>>It seems to me that Rp is Not the 100-ohm suppressor R. .
>
>> . Am I wrong on anything so far?
>
>Rp is the APPARENT parallel resistance of the whole network, as measured
>between the analyser terminals.
>
The numbers indicate otherwise.
>In an idealized parallel R-L network (no other sources of losses, no
>stray inductances or capacitances) Rp would always be identical to the
>resistor value, at all frequencies.
>
>In practice it is not. Losses in the L tend to make Rp lower. Stray
>inductance in series with the paralleled network tends to make the
>measured value of Rp larger (as I showed over the weekend, even a
>fraction of an inch of lead wire can have a major effect).
>
Is it reasonable that a 100-ohm suppressor R would measure: 100-ohms on
a DMM, 49-ohms at 10MHz (where Ls losses are minimal), 102-ohms at
100MHz, and 104-ohms at 200MHz? . If lead-length were causing an
appreciable effect, it would have produced a substantially different
result.
Rich...
R. L. Measures, 805-386-3734, AG6K
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