Warren, I may be teriible wrong but I understand Tom and his data so that PPS and 100 Hz have the SAME performance (what I had expected) with the PPS being able to be improved by the sawtooth correction. Attached are some seconds of data from my GPSDO which second Tom's measurements as far as the PPS is concerned.
> All else being equal, Tom's data says to me that a simple analog front end design when > combined with a microprocessor is able to provide a better performing GPSDO > than any digital only unit that is using just the 1PPS. Can you explain again why you are thinking this? Tom's claim is: For all tau beyond 1 second, the ADEV of the 100 Hz output exactly matches the ADEV of the 1PPS output. So, it does not matter whether PPS or 100 Hz are used, it is a question of the loop time constant only, which must be the same for both. Best regards Ulrich > -----Ursprungliche Nachricht----- > Von: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Im Auftrag von WarrenS > Gesendet: Samstag, 6. Dezember 2008 15:57 > An: Discussion of precise time and frequency measurement > Betreff: [time-nuts] Analog or Digital GPSDO? > > > > Here is a posting meant to start a debate between open minded > freq-nuts. It is inspired by Tom's latest posting at http://www.leapsecond.com/pages/m12-adev/ All else being equal, Tom's data says to me that a simple analog front end design when combined with a microprocessor is able to provide a better performing GPSDO than any digital only unit that is using just the 1PPS. It would appear that the analog front end can be as good and even better than using the sawtooth correction data. I may be a bit pregidous toward analog because I have been using analog only sub ns tracking of the GPS error signal for a long time. What analog or digital can not address is any of the issues concerning non carrier phase receiver limitations. so I'd like to assume for this discussion that the GPSDO is using a Motorola Oncore type of receiver with position hold capability. A different but related question is, does or would using some form of waas help a GPSDO? Have fun with it, WarrenS _______________________________________________ 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.
AOSChart.pdf
Description: Adobe PDF document
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