[time-nuts] Changing frequency of an HP 10811 oscillator

Richard (Rick) Karlquist richard at karlquist.com
Mon Nov 22 16:44:53 UTC 2010


Several issues here:

1.  Making a precision crystal like the 10811 one is very involved.
It cannot simply be rescaled to a different frequency.  It represents
a whole new design.  This is not like ordering custom crystals for
your 2 way radio (back in the day).

2.  The 10.23 MHz crystals I am going to give away (as time permits :-)
were designed under duress by the crystal designers who did not want
any part of the operation.  That's why I have a box of the crystals,
since the project died.  Expect a similar "welcome" from crystal vendors.

3.  Many years ago, it may have made sense to have 10.23 MHz GPS
time base oscillators.  Nowaways, it is much easier to synthesize
frequencies and you don't see this any more.  Everthing starts with 10 MHz.

4.  If you need 20.0000 MHz, then use a doubler as others have noted.
If you need some "random" frequency, use frequency synthesis.

5.  The 10811 crystal is in a custom can, and you would have to kluge
in any different crystal package.  This would probably screw up the
oven gain, necessitating rebalancing the heater transistors.

Summary:  (to use a technical term:)  fuggedaboudit

Rick Karlquist N6RK

On 11/21/2010 10:32 AM, Demian Martin wrote:
> Having seen the note on alternate crystals for the HP10811 oscillator I was
> wondering if its realistically possible to re-crystal one to frequencies in
> the 20 MHz range? Some other components may need to be changed of course but
> is this worthwhile exploring? Who would be a good vendor for a few custom SC
> crystals that would work in an HP10811? I have been quoted prices in the
> $500+ range for finished products and want to explore a more cost effective
> option before I spend a lot of money.
>
>
>
> Demian Martin
>
> Product Design Services
>
> San Leandro, CA 94577
>
> 209 613 6990
>
>
>
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