Falcon Wireless Tech Support - KF4HAZ wrote:
>> 50ppm/degC would be a terrible spec for a crystal.
>> I don't think you can get one that bad.
>
> I think I found one that bad once.
> I had ordered samples from different suppliers and one of the watch
> crystal type packages would actually change frequency everytime the AC
> turned on. Finally settled on HC49-U package from FOX, +/- 30 PPM (@
> 25c) +/- 30 PPM (-20c to 70c)

Was it really due to the temperature shift when the AC turned on?  Crystals
work on mechanical vibrations.  Especially low frequency crystals can be
influenced by external vibrations.  Maybe the air conditioner created enough
vibration of the right frequency that caused something else near the crystal
to vibrate near the crystal's frequency?


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