[TowerTalk] Measuring Common Mode Choke with Anritsu VNA

Máximo EA1DDO_HK1H ea1ddo at hotmail.com
Thu Jan 4 07:52:33 EST 2018

Morning all,

I am in same situation as Paul, learning lot of things from you, specially Steve, Jim, Wes, etc.

One of the new things that catch my attention was to calibrate the VNA with a higher value load, for example 1K Ohm.

Then, analyse a 10K (non inductive) resistor to see the performance.

I´ll try it next, hopefully during the weekend.

Thank you to all of you to share the knowledge with us.

73, Maximo

De: TowerTalk <towertalk-bounces at contesting.com> en nombre de Steve Hunt <steve at karinya.net>
Enviado: jueves, 4 de enero de 2018 12:43
Para: towertalk at contesting.com
Asunto: Re: [TowerTalk] Measuring Common Mode Choke with Anritsu VNA

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:

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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