[ntp:questions] NTP, GPSD & PPS

Sander Smeenk ssmeenk at freshdot.net
Tue Dec 9 19:35:21 UTC 2014

Quoting juergen perlinger (juergen.perlinger at t-online.de):

> This is a known weakness of the GPS18x series. The puck tries to center
> the serial output between the PPS pulses, and that's a pain in the back,
> pardon my French. But to be fair, some SIRF based modules do it even worse.

It appeared to me the sentences were well off the PPS signal itself when
viewing gpsmon output. Thanks for this, will dig into that a little...

> > The GPS provides 9600bps serial comms. Would it help to speed this up to
> > 19200bps? I've already disabled all NMEA sentence output for sentences that
> > "aren't useful for timekeeping" but at this moment i have to use external
> > clocks to sync against.
> Changing the baud rate does not really help with that device.

I've talked to some other 18x owners that reported lower speeds to be
more stable (4800bps) but in my experience 9600bps was more accurate.
(This was 'measured' with munin graphs over at least 24h periods).

> > Few questions:
> Since you run ntp4.2.6 under Linux, I know only one solution from my own
> experience:

Thanks for this information. Very helpful. I can work with this.

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