Re: Getting started with the nanoVNA guide


Jerry Gaffke
 

I don't feel I know something until I touch bottom with physical reality,
assuming such a thing exists.

In the case of the S parameters, that means describing them as a vector ratios
of two vector voltages, using complex number arithmetic:
https://en.wikipedia.org/wiki/Complex_number
https://en.wikipedia.org/wiki/Electrical_impedance
https://en.wikipedia.org/wiki/Reflection_coefficient
https://en.wikipedia.org/wiki/Scattering_parameters

Bottom paragraph of post https://groups.io/g/nanovna-users/message/1318
shows that I got hung up on that for awhile. Many sources did not
explicitly state S11 (for example) was a voltage ratio. I assumed it dealt with power,
like SWR. (Historically, some "S parameter" models did deal with power ratios.)

Baier's paper on correction factors has some great stuff, but does not touch bottom:
http://sdr-kits.net/DG8SAQ/VNWA/12_term_dg8saq.pdf
He never bothers to mention that all his variables are vector quantities.
Never describes what physical properties they measure.
Figure 1 shows a two terminal load ZL connected between the
lines representing the incident and reflected voltages (wrong!).
The TX-Oscillator port of Figure 1 is ignored in the math.

Maybe I should let HexAndFlex write that guide to the nanoVNA,
and I'll write a guide to help non-RF people like me navigate Baier's paper.

Jerry, KE7ER

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