[time-nuts] Question on crystal jumps
wb6bnq at cox.net
Thu Oct 23 10:42:42 UTC 2008
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
atomic filter with extremely narrow bandpass (i.e., with an extremely
The resonant frequencies of these atomic filters are up in the microwave
and thus do not lend themselves easily to direct comparison. So, a high
standard frequency oscillator is locked in a loop controlled by the
filter. The OCXO's output is the reference signal out of the atomic
I hope this rather simplistic overview answers your question ?
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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