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I was pretty excited about crystal measurements and crystal filter construction a few (many?) years ago. I homebrewed Jim Kortge's?PVXO and initially used a diode detector with good results. Later I built W1FB's integration of several W7ZOI circuits into one crystal measurement instrument that had appeared in QST.

Over time, I started using an?AD8307 type detector for the measurements. I'd built another W7ZOI circuit for this.

While writing the C# software for the PHSNA system originated by W5JH and N5IB, I decided to attempt to automate crystal measurements. I wasn't at all sure it would work, but in fact it worked very well and I was pretty proud of it. I could characterize a crystal and report Cm, Lm and Rs in about ten seconds. The starting point was to provide the approximate resonant frequency and the attenuation of the fixture with a short in place of the crystal. The program would?start a few hundred Hz below the resonant frequency?and move upward until the exact resonant frequency was found, recording the frequency and attenuation found, then scan down for the -3 dB point and then up from resonance to get the other -3 dB point. This was enough information to allow calculation of the parameters.

I've done crystal measurements with the nanoVNA. It's a wonderful gizmo, but the tiny size and those SMA connectors put me off a little. Yes, I use nanoVNA-Saver.

73

Nick, WA5BDU