I've read the HP article now and it looks like a really neat way to measure for series resonance. I think I can do this for the raw crystal and also with an accurate 30pF load capacitor. I need to make the load cap and I'll use a couple of ATC800B 15pF caps in parallel and check the capacitance on the VNA. I've checked/tested that my Mi2024 sig gen can do external FM with DC coupling and the very close in phase noise of the Marconi Mi2024 sig gen should be much better than the HP8640B at offsets of a few Hz at these test frequencies. So I think I'm good to go...
My old HP8405A VVM is now on the bench warming up and I'll leave it an hour or so to fully settle. I also need to make the RC loop filter. I'm tempted to make this in an inline BNC enclosure and I've got one somewhere...
This old HP app note deserves a Youtube video to celebrate the elegance of the method but sadly I don't have the presentation skills or the video making skills to do it justice. But I'll post up my findings on here over the next day or so
