A C wrote: > > So are you saying that the -52.888ms is making a significant > > contribution to the offset of -0.000001s ? > > Yes, if I disable the NMEA source with a "noselect" and leave the > Internet servers and the PPS clock (22) running, my overall system > offset drops and holds at a few tens of microseconds. If I leave it in, > the system offset wanders around. The magnitude of the wander appears > to correlate with the magnitude of the NMEA offset. For very large NMEA > offsets (sometimes exceeding +/- 50ms) the system itself starts to drift > away to large ms offsets. Overall I seem to get better performance > without the NMEA driver contributing than with it included hence the > desire to make it accessible only when all the other Internet sources > fail (but GPS is still working).
This doesn't make a lot of sense. NMEA is known to be pretty much useless without a PPS. So if your NMEA time data is "off" I gotta wonder if your PPS is "off" too. Does your GPS report any "health" information? > Both PPS and NMEA are coming from the same physical GPS just using two > serial ports, one for the PPS and one for the serial data (this split is > required due to serial port driver limitations). Are you *certain* that your GPS is producing a "locked" PPS signal when the NMEA time is wandering? H _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
