Electronics > Projects, Designs, and Technical Stuff

[Solved] NanoVNA says impedance of my 3200R resistor is 542R-1250X at 50 MHz

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hendorog:

--- Quote from: ogden on October 23, 2019, 09:37:42 pm ---
--- Quote from: hendorog on October 23, 2019, 08:27:24 pm ---Excellent, there is no need to proceed any further in that case.

--- End quote ---
Why don't you explain how FakeFlip works.

--- End quote ---

I can't help you there.

But I did keep looking for a good doc, and then I found this video which covers it perfectly I think.

ogden:

--- Quote from: hendorog on October 25, 2019, 04:27:33 am ---
--- Quote from: ogden on October 23, 2019, 09:37:42 pm ---Why don't you explain how FakeFlip works.

--- End quote ---
I can't help you there.

But I did keep looking for a good doc, and then I found this video which covers it perfectly I think.

--- End quote ---
Thanx! Apparently we both looked. I found this wiki page which covers your case perfectly I think.

virtualparticles:
This is a real can of worms. One-Path, 1-port calibration is also called "Enhanced thru" calibration. The two main contributors to S21 uncertainty are "Transmission Tracking" and "Isolation". The Isolation error, or the leakage from port 1 to port 2 within the VNA is usually below thermal noise in the measurement bandwidth of most VNAs. Unfortunately, the isolation of the Nano is quite awful, so this calibration must be performed. After calibration, the isolation cal should hold for an hour or so. After that one will begin to see the noise creep higher at the high end of the frequency band.

Transmission tracking is approximately equal to the sum of the products of the Raw Port 1 match and the Residual Port 2 match and the Raw Port 2 match and the Residual Port 1 match. To clarify the terms here, Residual means the "apparent" value after mathematical correction has been applied. A One-Path, 2 port VNA does not have a Residual Port 2 match calculation so the Transmission Tracking becomes a function of the sum of the Raw source and load matches alone. This results in ripples in the S21 measurement.

Thanks

BW

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