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Do the vibrations of aircraft engines (or any engine, for that matter) dilute the accuracy of a quartz clock?

I haven't done any kind of research or hypothesis testing, though I believe that the frequencies of both don't necessarilly line up enough to interfere with either waveform.

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    \$\begingroup\$ It can be an issue. See for example mwrf.com/active-components/… \$\endgroup\$ – Abe Karplus Jul 31 '18 at 23:54
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    \$\begingroup\$ Its probably not affecting the time keeping as it is averaged over a long period. However vibration (G's) modulates the frequency, creating phase noise. A lot of effort has to go into making low G sensitivity crystals for GPS for example, which get used in high shock and vibe environments. Sometimes resorting to exotic tricks like pairing matched and opposite crystals to get cancellation. At certain high vibe frequencies the mounts and the blanks can resonate, which is bad. In the old days, a good thump to your GPS made it lose lock because of this. \$\endgroup\$ – Henry Crun Jul 31 '18 at 23:59
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Crystals can be jarred on the mount interface and shift the frequency a significant amount. A ruggedized mount is available in more expensive types. A good supplier should have vibration and shock limits.

I have experience with shock & vibe testing ruggedized mounted SC cut Xtals with frequent failures in some axes but not all.

I also knew of one incident where NASA rejected a former colleagues product being oven tested with an unfortunate short height fall from a Tenney Jr. door, duct tape and a space instrument with a soldered Xtal onboard. NASA recalculated the impact of dropping 4" on the table top and rejected the unit in spite of normal operation from risk of partial shear of coldweld wirebond.

Any Xtals dropped on the floor should be trashed. Some parts may be better than others.

The key to Xtal vibration is the tiny motional capacitance. The modulation under vibration acceleration is possible but is attenuated like a high pass filter with a mechanical resonance. The abupt shift in frequency in ppm depends on the level of motion above some threshold.

Your concern is unanswerable without some part number, specification for vibration levels and acceptance criteria for shift, then test qualification of each source.

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