[time-nuts] Question on crystal jumps

Brooke Clarke brooke at pacific.net
Fri Oct 24 02:39:32 UTC 2008

Hi Steve:

There is no Rubidium oscillator.  See the block diagram at:
The amount of light passing through the Rb cell is used to steer a quartz 
oscillator.  In the case of the PRS10 it's an ovenized oscillator that's an 
improved and smaller version of their SC10.

Have Fun,

Brooke Clarke
http://www.prc68.com/P/Prod.html  Products I make and sell
http://www.prc68.com/Alpha.shtml  All my web pages listed based on html name
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Steve Rooke wrote:
> 2008/10/24  <SAIDJACK at aol.com>:
>> the jumps are very slow in their frequency change, so the crystal filters
>> would just follow the frequency drift. I have seen these jumps take from a few
>> seconds to 20 minutes or so. Of course in a Rb they would be compensated by
>> the  Rb pulling or pushing the crystal onto the proper frequency.
> But I'm not suggesting that the rubidium stage is used to discipline a
> ocxo and then fed onto a xtal lattice filter, I meant that the
> rubidium stage would go directly into the xtal lattice filter. This
> way there is no xtal oscillator to jump off frequency.
>> Also, the additional crystals in the filter will very likely jump too, so I
>> would expect the overall performance to actually get worse.
> If the jump is due to tiny physical effects on a crystal edge, as
> previously described, I would doubt that every xtal would be exactly
> the same wrt this and I very much doubt that all the xtals in a
> lattice filter would jump at the same time and in the same way. This
> type of filter works on the basis that each element suppresses signal
> outside its centre frequency. If one xtal changes it's centre
> frequency, all that changes is that the signal level at that stage
> output drops (as in an off-tuned tuned circuit in a multi-stage filter
> would do). Also the probabilities that every xtal would jump at the
> same time would surely be very high and I'm not sure that using a xtal
> in a filter circuit would be subceptable to this jumping in the same
> way as using it in an oscillator circuit.
> Now if the jumps were caused by something like a cosmic ray, I would
> expect that the xtal would just wobble off frequency rapidly and very
> quickly go back to its resonant frequency. Using a multi-stage xtal
> filter should circumvent this as the particle would have to physically
> strike all the xtals in the filter on it's path. Physical arrangement
> of the xtals in the filter would easily guard against that.
> If the jumps are caused by gravitational effects, it should be
> similarly possible to design the filter the be less prone to these
> affects by the orientation of the xtals.
> 73 - Steve

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