The challenge is to detect a failure of the GPS source (LOS) before the DPLL moves the OCXO.
I used to design Stratum clocks for a large telecom company, and I used several trick do detect a phase ramp on the digital phase detector; this was used to declare a probable bad source. At that point, we halted the movement of the DPLL and observed the phase detector activity. We had two DPLLs, and if both detected a phase ramp, we declared the source bad. -----Original Message----- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com]on Behalf Of Tom Van Baak Sent: Sunday, January 25, 2009 11:03 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Home made GPS disciplined atomic clock > I think that it should be a much better (in theory) than OCXO which > comes short therm stability (what I'm actually seeking for). It should > be much more accurate with long holdovers also. Right, it all depends on what stability you're after. The OCXO will have much better short-term stability than the LPRO -- the LPRO is close to ten times worse. So do not replace the TBolt OCXO with a LPRO if short-term stability is your goal. See: TBolt OCXO plots: http://www.leapsecond.com/pages/gpsdo/ http://www.leapsecond.com/pages/tbolt-tc/ LPRO plots: http://www.leapsecond.com/museum/lpro/ However, if long-term, GPS-unlocked, holdover performance is the goal, then using a Rb would make a good choice. > This is very simple modification by the way. Infact my original plan was > to use the 1PPS to synchronize the LPRO C-field with separate control > ... See John Miles work to replace the Thunderbolt OCXO: http://www.thegleam.com/ke5fx/tbolt.htm /tvb > Here's a link for the log: > http://www.amigazone.fi/files/gpsdo/tbolt-lpro-test.log > (Log format: TOW, PPS offset, DAC voltage, Disciplining mode & activity) I'll have a look at this; but it's not accessible for some reason. /tvb _______________________________________________ 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.