On Tue, Dec 11, 2012 at 5:55 PM, David J Taylor <david-tay...@blueyonder.co.uk> wrote: > > Gabs, > > I've seen similar jumps, and it happens when the GPS/PPS signal drops out > for a while. In my case, the GPS receiver is sitting just in an upstairs > room, not near a window or the root (as I normally have my other receivers). > > http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html#u-blox > > Watching a low-current LED connected to the PPS signal (through an > appropriate 680-ohm current-limiting resistor), I sometimes see the PPS stop > flashing. If it stops for long enough, NTP will revert to a different > reference. The hot-start may also result in a re-acquisition, and hence a > break in the PPS pulses. > > I now need a 10-channel 'scope, as I have Rapco 1804M, Trimble Resolution > SMT, a couple of Garmin GPS-18/x, Sure Electronics boards, and the u-blox > (navigation) receivers shown above. Comparing the PPS outputs they are all > within about 100 ns, more or less. <G> Quite adequate for running NTP on > my systems. > > Cheers, > David > -- > SatSignal Software - Quality software written to your requirements > Web: http://www.satsignal.eu > Email: david-tay...@blueyonder.co.uk >
David, I forgot to thank you for your helpful site and NTP plotter. I have the antenna outside with a 180 degree view of the sky, outages should be rare. Looking at the loopstats, the outage during the 4 us jump is about 12 seconds. This is a test server, I only have the LOCAL and PPS refclocks configured so during the outage the clock just flywheels. I agree these cheap GPS receivers are more than enough for a stratum 1 NTP server. How about a 10 channel TIC? I'm sure someone could suggest a way to do it, probably several PICTIC II's? _______________________________________________ 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.