[TowerTalk] Measuring Common Mode Choke with Anritsu VNA

Máximo EA1DDO_HK1H ea1ddo at hotmail.com
Sat Dec 30 15:41:35 EST 2017

Hi all,

I have in my hands a very nice device called "VNA Master" from Anritsu, model MS2025B.

The thing is I am trying to measure a Common Mode choke with this VNA, using S21 mode on the braid of a coax cable with different toroid combinations, but my knowledge is limited and I am not sure if this device is able to show the common mode on screen (I think is called "complex impedance").

The options available for the trace are:

Log Mag




Log Mag/2

Log Polar

Real Impedance

Imaginary Impedance

(Plus some more; SWR, Group delay, Linear Polar, Smith Chart, etc.)

Is any of the above types useful to show Common Mode Choke on screen?

Then , the Marker has some more options to show additional information.

Apart from above list, there are some extra options:

Impedance (Z)

Admittance (Y)

Normalized Impedance (NZ)

Normalized Admittance (NY)

Polar Impedance (PZ)

So, I am not sure if any of those options are good to shown the "choke impedance" on screen, without additional calculations.

What I can do, and in fact I do, is to export the measure in .s2p Touchstone format, then apply some maths on a excel sheet to convert LogMag and Phase to complex R, complex I, and finally complex Z. All of that on Excel.

But to get that directly on screen would be much better.

Thank you very much.

Happy New year.

73, Maximo

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