[time-nuts] Old Crystal.

[EB4APL]

Hi,

If you have access to a Network Analyzer, either Scalar or Vector,  you 
can measure the crystal parameters. You need a test fixture (homemade) 
to convert the impedance to 12.5 Ohm and you sweep the crystal to obtain 
its serial resonance and the -3dB points. From these there are formulas 
to obtain the motional resistance, inductance and capacitance, and the 
crystal Q.  Even some low cost hobby type analyzers have a mode for 
measuring crystals with these calculations integrated.

Regards,

Ignacio EB4APL

El 01/03/2021 a las 0:35, Dan Kemppainen escribió:
> Hi All,
>
> I've picked up a couple of old crystals. Mostly because they look 
> neat. They are 1Mhz, in a glass tube. The quartz is ~25mm dia, at 
> about 1 mm thick. Was able to get them to oscillate using a Colpitts 
> circuit. They will oscillate at 2.851Mhz (probably some strange mode)Â  
> if given the chance.
>
> I've been scouring my reference books here, and haven't had much luck 
> finding any details on how one would even guess at the parameters of a 
> quartz like this.
>
> There area few numbers on them, 33 stamped on the side, 1000 (KHz???) 
> on the top, 87 on the top, and hand written 501 (probably a SN). 
> Digging on line, I'd guess an AT cut based on thickness. I'm guessing 
> the 33 is capacitance in pF. 87, might be year.
>
> If any of you have any suggestions on where to find information on how 
> to get something like this to oscillate properly, guess at correct 
> parameters, or even measure any of the parameters I would really 
> appreciate it.
>
> I'm sure these are really nothing special, but it would be neat to 
> give them a fighting chance to show what they can or can't do without 
> breaking them!
>
> Thanks,
> Dan

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