Hi Paul,
No, I no longer use the 50 Ohm termination at the jig. I originally
included it because I was using long RG174 patch leads between the VNA
and the jig and wanted to minimise coax loss at the higher frequencies.
For the last year or so I've been using the jig arrangement shown here
without any termination:
http://www.karinya.net/g3txq/chokes/#measurement
Steve G3TXQ
On 04/01/2018 12:17, Paul Christensen wrote:
Steve,
Over the last week, I've been collecting articles and data on various S11
versus S21 methodologies for use with RF choke CM measurements. In your
S21 measurements, are you still using a resistive 50-ohm source generator
termination on your test jig? (See quote below from Owen Duffy, Ex-VK1OD)
If so, is it because the generator does not see Z=50+j0 that's present at
the VNA's detector port owing to the fact that a series complex Z (the RF
choke) is placed between ports? Is the termination necessary to obtain a
reasonably accurate complex Z and phase result as complex Z increases?
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