[SOLVED] Re: ntpd never achieves synchronized, even with PPS source; ntpdig KOD

[Achim Gratz]

Robin H. Johnson via devel writes:
> # ntpwait -v
> Waiting for ntpd to synchronize... OK! (186.4 seconds)
> # ntpdig
> 2018-12-18 11:27:53.262696 (+0700) +0.000006 +/- 0.000046 localhost ::1 s1 no-leap
> # ntpq -p -n
>      remote                                   refid      st t when poll reach   delay   offset   jitter
> =======================================================================================================
> xSHM(0)                                  .GPS.            0 l    3    4  377   0.0000 -138.015   4.0644

Still marked as a falseticker becuase the intersection algo throws it
out for having a too large offset.  If the ~138ms are reasonably stable,
consider configuring the refclock with the appropriate offset for
compensation of the systematic error.

> *SHM(1)                                  .PPS.            0 l    -    4  377   0.0000   0.3231   0.4445

The jitter on that PPS source still looks pretty large, is this via the
built-in USB interface of the GPS module?  I'm getting similar figures
from a uBlox-6 or uBlox-8 without PPS and for PPS via USB serial (FTDI)
down to about 200µs.  The actual clock source on that particular box is
via PPS-GPIO, the other two just get monitored:

     remote                       refid      st t when poll reach   delay   offset   jitter
===========================================================================================
 NMEA(0)                     .uBx8.           0 l    1   16  377      0ns 1.4352ms 610.47us
 NMEA(1)                     .navS.           0 l    4   16  377      0ns 169.87us 207.13us
oNMEA(2)                     .NavS.           0 l    -   16  377      0ns    107ns    187ns



Regards,
Achim.
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