[G0HZU_JMR]

I only had time to look at one of the 20 year old 4.032MHz crystals this evening on the VNA but the results were interesting. This crystal has a very high motional inductance and it is therefore quite 'stiff' in terms of its resonant frequency when the parallel capacitance is tweaked away from 30pF. But with 30pF loading on a simulator it was resonant at 4.032025MHz so was just 25Hz high. Changing the 30pF to 20pF on the simulator only shifted the frequency up 150Hz. Changing the loading to 40pF only shifted it down by about 30Hz.

I'll therefore make up a decent 30pF test cap tomorrow and test all 8 on the VNA for resonance. This will be better than trying them in an oscillator. I'm testing the crystals at a low drive level on the VNA to prevent any funny effects. I suspect that all 8 of these crystals will perform well in this test but I need to make up a socket based test jig for them and I'll do this tomorrow sometime.