I have noticed the sudden improvement of the PPS wander after the survey on a LEA-5T but the RMS wander is 30ns (see the timing appnote GPS.G6-X-11007 from uBlox) uncorrected and 15ns if sawtooth corrected. Your 3ns is strange, not the 30ns.
On Sat, Jan 17, 2015 at 1:03 AM, <[email protected]> wrote: > Hi All, > > I've been playing a Ublox 6T receivers on a synergy SSR-6Tru module. The > unit has been running as part of a GPSDO. In logging the phase between GPS > PPS and OXCO, a few days ago the normally small amplitude short term (10s to > ~500s) phase wander became rather erratic. For the previous several months > the short term wander was around +/- 3nS to 5nS. All of a sudden this jumped > up to about +/- 25nS. > Anyway, the guess was that it was GPS related. So the first step was to > verify GPS was still using the last survey-in points, which it was. The > modules was seeing 14 or 15 good birds at a signal strength of 35 to 50. For > kicks another survey in (48 hour) was started, which just finished up today. > As soon as the survey in completed the phase wander dropped back down to > about +/-3nS. The change was immediate, like a switch was thrown. The > antenna hasn't moved, but the corresponding survey coordinates from > September and January show a phase center position change of about 1.8m. > This seems like a pretty small number, and wouldn't have expected it to make > that big of a difference. At this point I'm not sure what to think. > > Has anyone seen any of the Ulbox 6T modules PPS suddenly get 'noisy'. Is > there anything else I should be looking at? > > Any recommendations on what I should be setting for NAV5 and NAVX5 settings > that could improve things? Elevation angles, or C/N thresholds? > > I'm quite puzzled by this sudden degradation of the system. > > Thanks, > Dan > > > _______________________________________________ > 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.
