Hi, The EFRATOM LPRO does not use a OCXO, just a straight quartz crystal oscillator. The control voltage swings around a volt as the base plate warms up. The time constant of the PLL that the XO is in must be quite short, a small fraction of a second so that the effect of drifting temperature has little effect on the output. I guess that all the crystal does is to filter what must be a quite noisy signal from the atomic resonance. When I inspected the circuit board I could not even find the crystal, it is not in a grand crystal can. cheers, Neville Michie
On 23/10/2008, at 9:42 PM, WB6BNQ wrote: > 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" <[EMAIL PROTECTED]> >> To: "Discussion of precise time and frequency measurement" >> <[email protected]> >> 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 >>> >>> >>> [EMAIL PROTECTED] 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 >>>> >>>> >>>> >>>> _______________________________________________ >>>> time-nuts mailing list -- [email protected] >>>> To unsubscribe, go to >>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>> and follow the instructions there. >>>> >>>> >>> >>> >>> >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/ >> listinfo/time-nuts >> and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/ > time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
