I mentioned to Tom that I had seen the xgps program duplicate a lot of its satellites when I missed a PPS. I noticed my GPSDO go into holdover so I quickly brought up xgsp and noticed it happening again. This screen showed a few times intermixed with a normal screen. I have no idea whether it's a bug in xgps or due to something coming from the Adafruit, but it's interesting, nonetheless.
http://www.evoria.net/Adafruit/Holdover.png Bob - AE6RV >________________________________ > From: Paul <tic-...@bodosom.net> >To: Discussion of precise time and frequency measurement <time-nuts@febo.com> >Sent: Friday, April 25, 2014 1:20 PM >Subject: Re: [time-nuts] GPSDO and holdover > > >On Tue, Apr 22, 2014 at 9:57 PM, Tom Van Baak <t...@leapsecond.com> wrote: > >> I have noticed skipped 1PPS on the Adafruit GPS also. > > > >I've always assumed this could happen but as a result of RF signal loss not >a glitch in the gps. So I've started recording event timestamp deltas >using the Linux kernel PPS interface. I read assert events (e.g. >1398449188.001000242#1741672) and compute timestamp and event deltas. If >the t delta is < .9 something horrible must have happened and if it's > 1 >some didn't happen assuming the event count delta is always 1. > >I wonder if this is a reasonable approach or if I'm being lazily >optimistic. I just started (and I haven't added a join with the valid fix >indicator yet) but I've had two missing pulses in the last 24 hours. > _______________________________________________ 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.
