Re: [chrony-users] Strange "loss of PPS lock"

[Rob Janssen <chrony-users@xxxxxxxxx>]

Those GPSDO's usually are professional units like Meinberg which are closely monitored.
(i.e. we get that PPS from a distribution board)
They do not go out of lock.  And if they would, they would not drift that quickly.

With "its lock source goes out of lock" I mean that on some sites where we have
our own GPSDO it is configured like:

refclock    PPS /dev/pps0 refid PPS prefer lock SHM
refclock    SHM 0 poll 6 refid SHM noselect

The SHM clock is synchronized from the serial data and will become "unreachable"
when the GPSDO indicates loss of lock via its serial telemetry.  Similar to what you
could do with NMEA (when using a GPS tracker that outputs both PPS and NMEA).
But the issue occurs on sites with and without this facility.

Rob

On 1/18/23 19:51, Bill Unruh wrote:
> It is almost inconceivable that either the gps or the ntp servers could drift
> that far unless there were a complete cutoff. Are your sure that the ntp
> sources are not really one single source (Ie all your sources are reliant on a
> single source which is drifting away?-- eg they are all sources which are run
> by a single company?)
> It is also possible that the gps receiver or the antennas are bad, and the gps
> receiver is simply free wheeling? Although I would not expect that to give
> seconds of offset.
>
> I have no idea what "its lock source goes out of lock" means for the PPS
> source.


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