Yes. I have already decided to do it. I want some feedback from the list before I get past the thinking stage though.
Initial rough calibration will be easy once the temp control is functional. Let every thing get nice and stable. Read Freq. Step 1 deg C. Wait 10 minutes. Read frequency. Step temp. 1 degC. etc. Plot the results. Compute the aprox peak of the parabola. Home in with .1 deg steps. OTOH consider the same design with a 40MHz or ???MHz TCVCXO. What would .1C (.01C?) room temperature control give you? Lots of different oscs might be suitable. The power cost will probably be higher than an OCXO - at least to start. But the range of things that might be done is wide. Or consider running an AT Cut crystal at its lower inflection point. It will probably age slower. But a thousand hour bake at the higher inflection point might be good. As I like to tell beginners - when you get close enough to fundamentals it is all made of rubber or silly putty. Simon Engineering is the art of making what you want from what you can get at a profit. >________________________________ > From: Tom Van Baak <[email protected]> >To: Discussion of precise time and frequency measurement <[email protected]> >Sent: Wednesday, December 12, 2012 5:20 AM >Subject: Re: [time-nuts] Stable Watch Clocks > >Hi Simon, > >Thanks for the URL. That's one of those tiny 6x2 mm crystals, 20 ppm crystals >(ouch). The tempco (-0.034 ± 0.006 ppm/ T²) is excellent, though. Now, you can >adjust rate; and temperature you can control. Notice they don't specify the >stability, which is the key to timekeeping. > >So I see a very interesting experiment/opportunity for you. Get one of these >xtals and have it generate 1PPS. Then: >1) measure the accuracy (vs. spec) >2) confirm the tempco (vs. spec) >3) measure the stability (note: no spec given) >4) measure the daily or monthly or annual drift (vs. spec) > >If you get one of these 32 kHz xtals, I'm happy to send you the other gear you >need, if you have the time to do the experiment(s). You'll end up with some >very nice plots and a wonderful article or series of articles for your >electronics blog. > >/tvb > ----- Original Message ----- > From: M. Simon > To: Tom Van Baak ; Discussion of precise time and frequency measurement > Sent: Tuesday, December 11, 2012 9:01 PM > Subject: Re: [time-nuts] Stable Watch Clocks > > > http://www.abracon.com/Resonators/AB26T.pdf > > > This quotes .038 ppm/C^2 delta T from the turn over point: > > > > http://www.iqdfrequencyproducts.com/app-notes/timekeeping/ > > The fly in the ointment is the aging rate of 5 ppm the first year >(13ppb/day) and 3 ppm (8ppb/day) after. > > I'm sure holding 1 degC is easy. .1 C with some care and .01 C - my >measuring eqpt ain't that good. So temperature ceases to be a problem. Is the >other stuff workable? > > I would go with a 32KHz crystal for a "production" version to make it easy >to multiply up to 10MHz. > > Simon > > > Engineering is the art of making what you want from what you can get at a >profit. > > > >---------------------------------------------------------------------------- > From: Tom Van Baak <[email protected]> > To: Discussion of precise time and frequency measurement ><[email protected]> > Sent: Wednesday, December 12, 2012 3:55 AM > Subject: Re: [time-nuts] Stable Watch Clocks > > > > Typical 32KHz clock crystals are very stable in frequency if you can >keep them > > close to the turnover temp. If you can hold 1 degC it is .04 ppm. > > That's far better than I thought. Do you have a reference for this spec? > > I agree you might be able to make one accurate to 0.04 ppm, however >briefly, but I've never seen one stable to 0.04 ppm. I mean, that's like 1 >second a year. > > > I currently have no method for testing such a rig for stability. > > Oh, the slipperly slope you are on. I have just the solution for you ... > > /tvb > > > _______________________________________________ > 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.
