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
Hello Maximo. The necessary setup places the choke as the series element of a voltage divider between the VNA output and input (with the VNA input Z as the load), with calibration performed at the po
Maximo, I don't think that instrument will allow you to see the Zcm of a choke directly on-screen. However, it looks like it will display |S21| directly. With the choke connected between the two port
Hi Maximo, The calculation you need in order to produce series impedance is this: Z = 100*(1-S21)/S21 Note that these are all complex values. If your VNA has built-in math capability, use that. Other
And remember that inductors have parasitic capacitance and resistance, that resistors have parasitic inductance and capacitance, all of which depend strongly on their construction, and that the resis
Maximo, Just measure the common mode choke just like a simple inductor, i.e., ignore the center conductor of the coax with which it is wound. Set the measurement to S11, and the format to Smith Char
Hi all, All sorted. This VNA is not showing Zcm on screen, but, it does show S21 LogMag and Phase at same time so you can see if LogMag value is targeting -30dB to -40dB, at Phase at low levels, then
Several issues here. See comments inline. OK. BUT -- it's NOT an inductor. See below. Also study k9yc.com/RFI-Ham.pdf Or study it in the ARRL Handbook. It was added in 2011. Set the measurement
Maximo, A test I use to assess the capacitance added by the test jig is as follows: Wind a high-Q air-cored coil and connect a small-value parallel capacitor across it. Measure its resonant frequency
"OK. BUT -- it's NOT an inductor. See below. Also study k9yc.com/RFI-Ham.pdf Or study it in the ARRL Handbook. It was added in 2011. " I advised a setup for the measurement like that for a simple
On 1/1/2018 6:10 PM, Avery Davis wrote: I apologize for not being more clear, but the point of the exercise is not to measure the complete complex impedance to within 10%, although you are right that
Hi Jim, One more question. regarding the voltage divider (from your slides) to measure chokes. Should I calibrate the VNA with that voltage divider connected? Thank you very much 73, Maximo _________
You keep saying that and I keep directing you to Kurt's paper that shows this is incorrect. http://hamcom.dk/VNWA/How%20to%20measure%20very%20high%20impedances-Deutsch%20DG3OK.pdf Avery, Somehow I fa
Hewlett Packard''s app note on this topic is well known, and my own attempts at measuring high values of Z using S11 resulted in large errors. 73, Jim http://hamcom.dk/VNWA/How%20to%20measure%20very%
73, Jim http://hamcom.dk/VNWA/How%20to%20measure%20very%20high%20impedances-Deutsch%20DG3OK.pdf if you're measuring 500 ohms (10:1) a 1% error in the voltage reflection coefficient is a 5% error in t
This Anritsu VNA can check and save S11 and S21 at same time. So, checking a choke I´ve save the .s2p file including both S11 and S21. This is the result: https://1drv.ms/i/s!AmG0n3993dIchjxswg_HvXxB
Next picture it is more clear than previous one. Same measurement, same choke, at same time, S11 red (Zmag), S21 blue (TL dB). Markers show 0.9 MHz offset. https://1drv.ms/i/s!AmG0n3993dIchj1NPdwk7pQ
Jim, I agree the error can be very large, but whether that error is significant depends on the application. The Keysight charts clearly show that using a professional-grade VNA, the S11 measurement
Wes, This is a most interesting paper on measuring high impedances, I just wish I could find it in English so I could read it ;-) 73, Avery, WB4RTP -- This email has been checked for viruses by Avast
The issue is not the value of the actual Z. The issue is that the reported peak Z frequency can be very far removed from the true value. Hence the problem. If you build a monster Z choke but it's