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Sunday, July 18, 2021

Alan Wolke W2AEW's Great Video on Using NanoVNA to Measure Amplifier Input Impedance and Gain

Alan Wolke W2AEW is a true wizard.  We are all lucky to be interested in homebrew radio at the same time that he is sharing his knowledge and wisdom via YouTube. 

The ability of the NanoVNA to measure circuit impedances is, in my mind, one of its most valuable features.  With this, we can MEASURE input and output impedances.  We can put bits and pieces of circuitry together without wondering whether or not we were introducing impedance mismatches.   

But I had trouble getting good NanoVNA impedance readings on my TIA amps. I wrote to Alan about this and he pledged to make a video about how to do it right.  That video was posted to YouTube today (see above).  

Not only did I learn how to get a good impedance reading, I really learned a lot by just watching Alan move around through the various NanoVNA screens.  I want to be able to do that too!  I want to monitor the Smith Chart, and gain, and SWR, all at the same time.  Yes I do!  I also now realize that I have to order a bunch of those cool PC board SMA female connectors from Bezos. 

Thanks a lot Alan.  


  1. Great video! Logically presented and clearly described. The only thing I could suggest to improve it is to show how termination insensitive the amp is by looking at S11 while opening and shorting the amplifier output. A look at amplifier output impedance, S22, and reverse isolation, S12, would also be instructive.


  2. Thanks for posting this Bill, and glad this video is useful to you all.

    Joe - I have to leave *something* for the viewers to investigate on their own!

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  4. Excellent video Alan. Something I would have never thought of and would have left me scratching my head over.

    Glad Bill reached out to you.


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