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Re: Crystal Oscillator Stability



>From your numbers, I calculated an average stability of 1.32 PPM over the
full tested temp range (a freq deviation at the crystal freq of about 11.7
Hz.). Looking at the International Crystal web site, they rate the
temperature stability of their TCXO product at 2.0 PPM over a range of -20
to +70 C. The temperature stability of a standard HC49U crystal is +/- 50
PPM over the same temp range.

I would say you did a pretty good job !  I doubt you could make it much
better without getting much more complicated.

Howie
AB2S
----- Original Message -----
From: "Douglas Braun & Nadia Papakonstantinou" <dougnad@bellatlantic.net>
To: <amsat-bb@AMSAT.Org>
Sent: Monday, January 22, 2001 10:37 AM
Subject: [amsat-bb] Crystal Oscillator Stability


> First of all, I'd like to thank everybody who sent
> me data and suggestions on improving the stability
> of the oscillator on my DEM S-band convertor.
>
> I ordered and installed one of the PTC thermistors,
> soldering it to the crystal and feeding it with
> a 9-volt regulator.  I also fitted a lovingly hand-crafted
> hollow styrofoam cube over the crystal for insulation.
>
> After running it for couple of weeks, I observe
> a positive change of frequency with temperature:
> Moving the convertor from my shack to the attic
> (and back a couple of times) results in a ~3 kHz
> frequency shift for a ~40 degree F temperature change.
>
> This is about .05 PPM per degree C,
> or 5*10^-8 per degree.
>
> Does this sound reasonable for an oven-ized crystal?
> Would there be any worthwhile way to further improve
> the stability, without oven-izing the entire unit?
> BTW, my circuit has the RF choke across the crystal,
> and uses the RSK-1 transistors.
>
> Thanks,
>
> Doug Braun
> NA1DB
>
>
> ----
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