Hello Bruce, Hello Said despite the fact that the author is a ham radio colleage of mine I agree completly to what both of you said.
>Obviously, the longer you integrate the 1PPS GPS signal for, >the better the accuracy will be. But the drawback of this >is that the longer the integration time (averaging cycle), >the more the VCXO will (or might) drift. Of course, the >better the VCXO, the more stability you will get. But this >is hard to specify, let alone quantify. Who writes something like this has no good idea about the theory! Draw the tau-sigma of the receiver alone and draw the tau-sigma of the VCXO alone and look where the lines cross. Then you know EXACTLY which time constant you have to choose for the control loop without the slightest guess. And yes, don't forget to throw the Garmin out of the window! bye Ulrich Bangert, DF6JB > -----Ursprüngliche Nachricht----- > Von: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Im Auftrag von [EMAIL PROTECTED] > Gesendet: Samstag, 21. Oktober 2006 08:30 > An: time-nuts@febo.com > Betreff: Re: [time-nuts] The VE2ZAZ GPSDO > > > > > Hello Bruce, > > I agree. The DAC reference is an LM7805CT regulator with > 0.8mV/C (typ.) > temperature coefficient. Considering that typical Oscillators > (MTI units for > example) have about +-20Hz deviation per 5V - this alone - > excluding the Opamps > tempco, would lead to a temperature drift of 0.32Hz over a > 50 Deg C temp > range. That's about 3.2E-08, quite a bit worse than a good > surplus oscillator. > > And the 7805 does not have a maximum tempco rating, so it > could be 10x worse > than that... > > bye, > Said > > > > > _______________________________________________ > time-nuts mailing list > time-nuts@febo.com > https://www.febo.com/cgi-> bin/mailman/listinfo/time-nuts > _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
