[G0HZU_JMR]

Sorry to dig up a fairly old thread but I knew I had some old/decent 10MHz xtals here somewhere and I found the old sample bag today. It's always the same... I find 'lost' things when I'm looking for something else that is lost.

Back at work in 1993 I designed an RF converter that needed a fairly decent (but cheap!) crystal reference. A TCXO or OCXO was way too expensive and I got a bag of samples from IQD. The spec for these was:

CRYSTAL 20/10/20/30 10000KHz IQD

I think this is , 20ppm initial calibration, 10ppm over -20 to +70degC and 30pF load capacitance.

Sadly, I've only got one unused one left in the IQD sample bag, there were originally 10 of them. The bag is dated July 1993 by IQD.

I stuck the crystal on my E5071 VNA this evening and took a two port model of it. Note that my VNA has the snazzy 1E5 OCXO option fitted and so it can measure frequency very accurately. This measurement also required a narrow RBW and some averaging on the VNA but the exported VNA model showed on a simulator that with a 30pF loading it would be resonant at 9.999936MHz. The VNA reference plane was set right at the crystal legs.

This is only out by 64Hz and is well within spec even today. I haven't tried it in an oscillator but the VNA method should be the most accurate. I could try resonating it with a 30pF capacitor and measure it again on the VNA but I think this would be slightly less accurate due to strays and the accuracy of the 30pF test cap at 10MHz.

Back then this was a fairly serious 'standard' crystal because of the initial ppm spec and the spec over temperature. But it looks like it is still in spec today for initial calibration.