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Old 11th Jul 2022, 1:00 pm   #94
G0HZU_JMR
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Join Date: Sep 2010
Location: Cheltenham, Gloucestershire, UK.
Posts: 3,077
Default Re: 6-gang FM stereo tuner heads

I think that the classic RLC model of a quartz crystal is slightly flawed because it doesn't include any shunt capacitance to free space.

I did some crystal testing a few years ago and noticed a subtle difference between s11 and s21 measurements. I think this is partly caused by distributed reactance in the crystal and this isn't included in the classic crystal model.

I found that the parallel resonance frequency is shifted slightly if measured with a VNA in s11. I'm not sure if this is an error because of the effect of any distributed capacitance within the structure of the crystal. If there is distributed capacitance then I'd expect to see a difference in the parallel resonance when comparing the null frequency in s21 against the parallel resonance frequency measured with s11.
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