Dan Drown writes: > The GPS module I'm using still outputs PPS even when it loses lock. > That won't be true for every GPS module.
I also have a NavSpark mini attached at the moment and I was surprised it kept outputting the PPS when losing 3D lock (it stops blinking the LED). It seems semi-documented to keep the PPS on if it at least sees one satellite, although the corresponding settings can't be read or altered (that seems resereved for the timing firmware, on the mini I just get an NACK response). Losing 3D lock happens about once or twice a day for me at the moment, probably because of a somewhat too agressive mask settings. It usually lasts less than half an hour with negligible effect on ntp. > My results were a long term average of 250us-500us lost per day > (~3-6ppb). This surprised me because of how low it was, I assume I > got lucky with the long term average temperature of the GPS module. Recently I've had an extended loss of lock and it was in fact drifting by about 1ms/hour. It may have been the result of some sort of power fault, since I've needed to reboot the Pi and powercycle the mini to recover. > Of course, this data doesn't apply to all GPS outage situations. But > it does suggest that holdover within 30ms is easy for the "can't hear > the satellites for a few hours" case. You might want to play with the elevation and CNR mask settings and check what happens with just one or two satellites considered in view. I think the degradation there is actually larger than when it is in complete holdover. Regards, Achim. -- +<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+ Samples for the Waldorf Blofeld: http://Synth.Stromeko.net/Downloads.html#BlofeldSamplesExtra _______________________________________________ devel mailing list devel@ntpsec.org http://lists.ntpsec.org/mailman/listinfo/devel