#326: How to Measure the impedance of "unknown" coax using a NanoVNA @w2aew

Uploaded January 2021 | Updated September 2026, 2 weeks ago

This short tutorial video shows how to use the NanoVNA to measure the impedance of an unmarked piece of coax transmission line. It uses the unique impedance transformation that occurs with a quarter-wavelength transmission line. By measuring the resistive component of the line at a frequency at which the line is a quarter-wavelength long, the unknown line impedance is simply the square root of the product of the termination impedance and the measured value.
See this playlist of additional tutorials using the NanoVNA:
youtube.com/playlist?list=PL4ZSD4omd_AylEyNCQYR3RcEb0olukPEJ
Notes from this video can be found here:
qsl.net/w2aew/youtube/unknownCoaxZ.pdf

#326: How to Measure the impedance of unknown coax using a NanoVNA

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