[time-nuts] Question on crystal jumps

Bob Q quenbob5 at pacbell.net
Thu Oct 23 15:36:11 UTC 2008


So why would they not show the same kind of jumps as plain OCXO's?  Rick K. 
mentioned atomic standards avoid jumps.
Bob Q.
----- Original Message ----- 
From: "WB6BNQ" <wb6bnq at cox.net>
To: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
Sent: Thursday, October 23, 2008 3:42 AM
Subject: Re: [time-nuts] Question on crystal jumps


> Hi Bob Q,
>
> Yes Rubidium (Rb) and Cesium (Cs) standards use OCXO's.
>
> I suppose the way to look at it is the Rb or Cs chamber acts as an
> invariant
> atomic filter with extremely narrow bandpass (i.e., with an extremely
> high Q).
> The resonant frequencies of these atomic filters are up in the microwave
> regions
> and thus do not lend themselves easily to direct comparison.  So, a high
> quality
> standard frequency oscillator is locked in a loop controlled by the
> atomic
> filter.  The OCXO's output is the reference signal out of the atomic
> standard.
>
> I hope this rather simplistic overview answers your question ?
>
> Bill....WB6BNQ
>
> Bob Q wrote:
>
>> Do rubidium standards use an OCXO?
>> Bob Q.
>>
>> ----- Original Message -----
>> From: "Rick Karlquist" <richard at karlquist.com>
>> To: "Discussion of precise time and frequency measurement"
>> <time-nuts at febo.com>
>> Sent: Wednesday, October 22, 2008 2:23 PM
>> Subject: Re: [time-nuts] Question on crystal jumps
>>
>> > I'm not quite sure what the question is here, but when
>> > we made 10811 oscillators at HP, "jumps happened".  Some
>> > crystals were better than others, but no crystal was immune
>> > from jumps.  With good quality crystals, you might be able
>> > to put an upper bound on the magnitude of jumps, like 10-9,
>> > but not on the time between jumps.  I also noticed that there
>> > didn't seem to be any correlation between jump activity
>> > and stability between jumps.  You could have an oscillator
>> > with really low aging, say a few parts in 1E11 per day that
>> > looked really good for quite a while, but then the frequency
>> > jumps.  After you've controlled everything you can about the
>> > crystal process, the electronics, the oven and the environment,
>> > you are still left with jumps.  If you want no jumps, go to
>> > an atomic standard like rubidium.  There are mechanisms that
>> > can cause jumps in rubidium standards as well, but good
>> > rubidium standards don't jump.
>> >
>> > Rick Karlquist N6RK
>> >
>> >
>> > iovane\@inwind\.it wrote:
>> >> I would be very pleased to know when (date and time) anybody
>> >> out there happened to record jumps in frequency of crystals.
>> >> I have stable (e-07) tuning forks which happen to jump too,
>> >> and I don't understand why, even having under control
>> >> temperature and air pressure. Sometimes they return to their
>> >> prior frequency with another jump, and this could happen even
>> >> days later, sometimes they jump and then recover smoothly the
>> >> prior frequency in a short time (such as one hour).
>> >> I have no idea whether any correlations would exist between
>> >> crystals and tuning forks jumps, regarding the causes that
>> >> could trigger metastability, and hence I would have a look at
>> >> crystal data in order to improve the base for future
>> >> speculation.
>> >>
>> >> Thanks in advance.
>> >> Antonio I8IOV
>> >>
>> >>
>> >>
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>> >>
>> >
>> >
>> >
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