Hi jmr,
Well, it's an interesting methodology for sure. I do have a Nanovna which I bought purely for evaluation purposes, but I have two proper lab-grade HP VNAs as well. Can't recall the model numbers off hand but one's good to 1.3Ghz and the other to 6Ghz (expanded from 3). Unfortunately the matching S parameter test set? for the 6Ghz one tops-out at 3Ghz, however, which is a bit of a nuisance. Still, since we are only talking 1.4Mhz (virtually DC :-)) for this test, none of that fancy stuff is necessary anyway. :-)
Jinxie
Jinxie