Yes, the sawtooth correction is limited to tens of ns and is rapid: 10 to 30 seconds usually, the wander is larger and very slow. If you want to build a simple GPSDO with a PPS output and disciplined by the GPS PPS, take a look at my design: http://www.c-c-i.com/exchange/ file: PiAutoTIC1.zip
On Tue, Apr 23, 2013 at 12:39 PM, Daniel Ginsburg <[email protected]>wrote: > > On 23.04.2013, at 12:50, Azelio Boriani wrote: > > > Daniel, > > a timing GPS receiver is not a GPSDO so its PPS is wandering about the > > nominal position. Using a digital oscilloscope, I can see how much the > > total wander is by activating the infinte persistence mode of the > display. > > After 10 minutes, 1 hour, 1 day or whatever you have an idea of the total > > "coverage" of the wander. The trigger comes from a Z3815A reference. To > see > > the "dance" of the PPS coming from a GPS receiver, a simple crystal > > oscillator as a reference is enough: use your microprocessor to generate > a > > PPS from its clock and visually compare this generated PPS with the GPS > PPS > > by a 'scope. > > > > Ah, I see now. Preoccupied with issue at hand I wasn't attentive enough > and I somehow thought that you were talking about 112ns wide sawtooth, > while in fact you were talking about wander in sense of ... well ... > wander. Sorry for the confusion. > > > > > On Tue, Apr 23, 2013 at 7:49 AM, Daniel Ginsburg <[email protected] > >wrote: > > > >> > >> On 23.04.2013, at 6:15, Hal Murray wrote: > >> > >>> > >>>> I wonder, what kind of timing GPS gives 112ns wander? > >>> > >>> How good is your antenna? 112 ns is roughly 112 feet. That's not at > all > >>> surprising if your antenna is inside or under trees. > >>> > >> > >> > >> Not perfect, but should be reasonably good. It's an external magnetic > >> antenna on my windowsill. > >> Anyway, +-400ns I'm seeing translates to +-120m in position. My surveyed > >> location is better than this. > >> > >>> You might watch the number of satellites and/or watch the position > while > >> it > >>> does a survey. > >>> > >> > >> 6-10 SVs, with PDOP in range 1.6 - 3.9 (about 2.0 most of the time). > >> > >>> > >>> -- > >>> These are my opinions. I hate spam. > >>> > >>> > >>> > >>> _______________________________________________ > >>> 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. > > _______________________________________________ > 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.
