[time-nuts] Making a HP 10811 better

Rick Karlquist richard at karlquist.com
Tue Sep 20 00:56:38 UTC 2011


The SC cut has turnover points located symmetrically
above and below the "inflection temperature".  The 10811 crystals are cut
to pull these turnovers close to the inflection point,
or they merge and you don't even have a turnover technically.

The E1938A crystals we just like the 10811 crystals, only
in a lower height package, except that the cut was changed
slightly to give turnovers of over 100 degrees, to allow
85 degree ambient operation.  There was also a lower turnover
around 70 degrees.

I'm not aware of there being any turnover below room temperature.

Rick



Tom Van Baak wrote:
>> This is mentioned in the HPJ article on the 10811.
>> (Required reading for anyone playing with 10811's).
>>
>> Rick Karlquist N6RK
>
> Indeed. For the rest of you please note the cover photo is
> worth it even if you don't read the article:
>
> "SC-Cut Oscillator Offers Improved Performance"
> http://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1981-03.pdf
>
> ---
>
> IIRC this is one of the articles that mentions in passing that
> the 10811 (SC-cut) isn't actually operated at the turn-over
> point, something, I think, that was more important for AT cuts.
> I'm looking for the other paper I read recently that discussed
> this aspect of the SC-cut.
>
> ---
>
> Speaking of turn-over points. Some crystal cuts have both a
> low temperature and high temperature turn-over point. Does
> anyone know of a crystal oscillator that is specifically operated
> at the low temperature point (and I'm not talking about exotic
> cryo sapphire here)? Maybe something around -20 C. In the
> range of a TEC cooler at least.
>
> The reason for the interest is that it seems to me some of the
> oscillator characteristics (such as drift or phase noise) might
> be related to temperature, in which case a well-below ambient
> temperature is better than a well-above ambient temperature,
> even if it complicates the packaging or thermal regulation.
>
> /tvb
>
>
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