HI Some simple empirical data:
1) Jumps tend to get further apart as the oscillator ages. 2) AT's have larger jumps than SC's. 3) A typical SC jump is below 1x10^-9 4) It's not a lot of things (spurs, drive, temperature, load,stress, micro-fractures, plating defects) if you need to explain all cases = they don't explain all events 5) It can be a lot of things (spurs, drive, temperature, load, stress, micro-fractures, plating defects) in some cases = they do explain some events The first published data I have seen on jumps is in a Fairchild Semiconductor App note from the late 60's / early 70's. They built a JFET based oscillator and it jumped…. Bob On Nov 29, 2012, at 7:30 PM, Volker Esper <ail...@t-online.de> wrote: > ...imho it has indeed jumped back, see the picture of 1643 GMT today. You > recognize the peak down yesterday at about 1900 GMT, then a smaller peak up > at about 2300 GMT and - after having a troubled night - again a peak up. The > EFC voltage now is nearly the same as prior to the "impact series". I suppose > it's actually a "crystal jump". > > In 1997 HP wrote in it's AN 200-2 (Fundamentals of Quartz Oscillators): > "...Crystals having unwanted signals could also shift from one resonate point > to another producing a frequency jump which would be an undesirable effect." > > IEEE has some experience with that phenomenon, too. An article from 1996 can > be found in their Digital Library > > http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=559877&url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel3%2F4090%2F12100%2F00559877.pdf%3Farnumber%3D559877 > > wich deals with that issue: > > "In this paper recently classified intermittent and discrete frequency jump > phenomena are briefly reviewed and currently not well understood abrupt > frequency jump phenomena are analysed and discussed in detail." > > John R. Vig writes in his "Quartz Crystal Resonators and > Oscillators For Frequency Control and Timing Applications - A Tutorial" > (2004): > > "It is the changes in the stresses, and the changes produced by the stresses > that cause frequency instabilities. There exists evidence that, on a > microscopic level, stress relief is not a continuous process. It can occur in > bursts that can, possibly, contribute to noise and frequency jumps." > > Numerous articles discuss the effects of contamination and failures of the > crystal clamp that obviously contribute to the phenomenon. > > Though very interesting stuff, that all sounds kind of academical to me. Now > I know it could be possible, that my GPSDO suffers from that cause. However, > since I don't know if or when or how often the effect recurs, I am the one, > who has broken nights now... > > I'll keep a jealous watch over the diagrams... > > Volker > > > > > > > Am 30.11.2012 00:14, schrieb Dennis Ferguson: >> >> On 29 Nov, 2012, at 02:32 , Charles P. >> Steinmetz<charles_steinm...@lavabit.com> wrote: >> >>>> This is a classic crystal jump. The crystal changed its frequency >>>> magically from one second to the next and the software compensated for it >>> >>> Here is another example of a 3805 having a bad moment. For just about two >>> minutes, it reported a phase jump of nearly 3 uS and then immediately fell >>> back nearly to its previous baseline, settling to the baseline in about an >>> hour and not requiring any longer-term change of the EFC voltage. This >>> does not look like a typical crystal frequency shift to me, but I cannot >>> rule that out. It looks more like what I'd expect to see if I set the >>> cable delay to 3 uS for 2 minutes, then back to 0. >> >> I think I would be more likely to call this one, where the crystal jumps >> to another frequency for a while and then jumps back to about what it was, >> a "classic crystal jump". I've seen this before, though not as large as the >> change you show. I hear these raise hell when they try to use PTP to >> transmit >> telecom-quality timing over asynchronous ethernet because it is hard to run >> a PTP control loop tight enough (i.e. at a high enough data rate) to correct >> that before it does damage. >> >> I think the other problem, with the crystal jumping to another frequency and >> apparently staying there (I'm assuming it hasn't jumped back), could have a >> broader range of causes. >> >> Dennis Ferguson >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> > > <DF9PL_GPSDO_2_20121129_2137_PPS-TI.jpg><DF9PL_GPSDO_2_20121129_1643_PPS-TI.jpg>_______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
