Using the NanoVNA to measure devices that have a UHF series connector – reader challenge

Using the NanoVNA to measure devices that have a UHF series connector left readers with a challenge:

An exercise for the reader: what would the e-delay need to be to compensate an s21 measurement if two identical cables were used to connect a UHF-UHF DUT?

So, by calibrating the e-delay in the referenced article, we measured the two way propagation time to be 3.0nS, one way is 1.5ns.

So is the answer to the challenge:

1. 1.5ns;
2. 4.5ns;
3. 3.0ns; or
4. something else.

(4) something else.

The s21 calibration was done with some fixture between Port 1 and Port 2 jacks, in my case it was a 200mm RG316 cable for which I measured the propagation delay to be 0.95ns. Since this is missing using just the the two SMA(M) to UHF(M) cables (1.5ns each), the new one way propagation time is 1.5+1.5-0.95=2.05ns.

The upshot of this is that the e-delay for s11 correction is different to that for s21 correction. The firmware does not allow for specification of different e-delay for each.