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G0HZU_JMR · 15th Feb 2018, 10:19 pm

For completeness, I changed the frequency on the Mi2024 to 10MHz and tried the IQD 10MHz crystal that I tested on the VNA yesterday.

On the HP8405A setup (after a fresh zero calibration) the counter read 9.999975MHz with the 30pF load cap. On the simulator with a perfect 29.8pF cap the VNA/simulator predicts resonance at 9.999960MHz so it was within 15Hz and the room temp feels about the same as yesterday.

See also below for a comparison of my LCR model of the crystal compared to the real 10MHz crystal on the VNA. You can see that the traces match almost perfectly so the lumped model is very good here too. I generate this model using the simulator and with an iterative approach the simulator can optimise the model values for motional L, C and R to fit the VNA data for the real crystal.

15th Feb 2018, 10:19 pm	#34
G0HZU_JMR Dekatron Join Date: Sep 2010 Location: Cheltenham, Gloucestershire, UK. Posts: 3,077	Re: Quartz crystal accuracy over time For completeness, I changed the frequency on the Mi2024 to 10MHz and tried the IQD 10MHz crystal that I tested on the VNA yesterday. On the HP8405A setup (after a fresh zero calibration) the counter read 9.999975MHz with the 30pF load cap. On the simulator with a perfect 29.8pF cap the VNA/simulator predicts resonance at 9.999960MHz so it was within 15Hz and the room temp feels about the same as yesterday. See also below for a comparison of my LCR model of the crystal compared to the real 10MHz crystal on the VNA. You can see that the traces match almost perfectly so the lumped model is very good here too. I generate this model using the simulator and with an iterative approach the simulator can optimise the model values for motional L, C and R to fit the VNA data for the real crystal. Attached Thumbnails __________________ Regards, Jeremy G0HZU