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Thanks Steve.

I had another thought on this subject last night and I cobbled together a quick test. Stable frequency generators and high resolution counters might not be on everyone's bench. For fun, I wired up one of my Si5351 VFOs (a KitsAndParts Uni-VFO) and configured it to cover the range of frequencies of the 8MHz crystals I was testing. In "debug mode", the Uni-VFO outputs the relative frequency on a computer terminal. After the VFO, I put a resistive attenuator (simple 5k trim pot and 51 ohm resistor), then a simple low-pass filter at 10MHz. I turned it down to -20dbm output. I used that to feed Jim's (K8IQY) crystal test fixture that has two transformers to put the crystal in a lower impedance environment. The VFO has a 1Hz resolution, and is very stable after a few minutes of warm up.?

I measured a couple of the original test crystals again using this setup. The numbers were all within a few percent.?

So, it seems that you could use any of the many Si5351 VFOs out there, assuming they can be set for a 1Hz resolution, as a frequency source for this test fixture. It eliminates the need for an expensive RF generator and frequency counter. The only thing that is a little exotic in my setup is the RF voltmeter. I think you could easily put together a two-diode RF probe and just watch the DC voltage on a meter to find the peak and -3db points. Even better, wouldn't it be cool to automate the process?

73

Mike M.? KU4QO