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Common mode choke measurements using VNA-QT #hardware


Dale Parfitt 2021/01/30 08:01

I am attempting to characterize some common mode chokes- comparing S11 and S21 measurement techniques. I would like to be able to view the real part of S11 and S21 up to perhaps 2000 Ohms. When I go to Set Graph Limits it only shows dB settings. Am I missing something?

Tnx,
Dale W4OP

Michael 2021/02/02 11:37

Dale,

I'm working on learning this also.
I built a jig for testing CMC's and other parts, from a BNC cable, would be easier if you have N connectors, but I have N to BNC adapters.

Do the SOLT calibration at frequencies you want. For the "Thru" cal, short out (clip) your two leads.
I'm currently using 1 to 30 MHz.

I have 2 traces setup:
Trace 0 is setup for Reactance (under the Format/More/Reactance) Scale is set to 10/Div right now. Shows the reactance.
Trace 1 is setup for LogMag (under Format/Logmag) Scale is set to 10/Div right now. Shows the Loss at the different frequencies.
NOTE That you may have to change the Scale to keep the traces on the display, depending on the values of your measurements.

Give that a try.
--
Mike, W0IH

Dale Parfitt 2021/02/02 15:06

Thanks Mike,
I have gone back to NanoSaver as it auto scales the ordinate axis.
Are you making S11 R+/-JX plots or S21 Z plots?
Dale W4OP

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