Peter, are these GPSDOs homebuilt units following the concept as published in the German ham radio magazine "cq-DL" some years ago?
Best regrds Ulrich, DF6JB > -----Ursprüngliche Nachricht----- > Von: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Im Auftrag von Peter Vince > Gesendet: Sonntag, 22. April 2007 15:09 > An: [email protected] > Betreff: [time-nuts] Newbie question: GPSDO filtering principles > > > Hello all, > > The recent talk about the ideal GPSDO has reminded this > newbie of a question I hope someone might be able to simply > answer: we have a couple of Rubidium GPSDOs which track in > the long term, but their phase drifts by several hundreds of > nanoseconds with an irregular, but roughly daily, pattern. > The units have a log output which shows the changes to the > EFC DAC, and this changes usually after a period of 8192 > seconds - sometimes longer, but rarely less. I understand > the need to average the GPS reading over this sort of period, > but by only changing the EFC at this period leads to > comparatively wild frequency swings - parts (plural!) in 10^11! > > I was wondering if a "sliding window" scheme would be > better - average over a period of, say, 8192 seconds, but > recalculate this average more often - say every hundred > seconds. The problem would be that having applied a > correction to your oscillator, subsequent averages would be > difficult as the slope of the readings before and after the > correction would be different. Perhaps you could process the > old data to remove the slope of your recent correction? > Another option would be to use a DDS, and then readings > wouldn't be affected by your corrections, and so long term > averages could be taken over any period. But the > disadvantage would be that you would have no feedback, and > hence not know if you applied an appropriate amount of correction. > > Hmmm, the brain is spinning with all the possibilities > and problems! Can some provide a quick explanation of the > way it is (properly) done, or is there a website that discusses it? > > Thanks, > > Peter > > > _______________________________________________ > time-nuts mailing list > [email protected] > https://www.febo.com/cgi-> bin/mailman/listinfo/time-nuts > _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
