[ntp:questions] FreeBSD and SureGPS

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Wed May 2 19:08:02 UTC 2012

fRANz wrote:
> I played with a Sure GPS board

Is it sending only one sentence?

> ntpd 4.2.6p2 from FreeBSD packages;

You might also try a more recent version:

>      remote           refid     st t whn poll rch    dly  offset jitter
> =======================================================================
> xPPS(1)          .PPS.           0 l  11   16 377  0.000   5.321  2.636
> oGPS_NMEA(1)     .GPS.           0 l  10   16 377  0.000   5.285  2.651
> xkraken2.bilink. 2 u 396 1024 377 63.208 -23.734 26.911

The o in front of GPS_NMEA indicates it the PPS prefer.

> ntp# cat /etc/ntp.conf | grep -v ^#
> server mode 18 minpoll 4 prefer

You may want to remove that prefer,
 and add one below on

> fudge flag3 1
> server mode 18 minpoll 4

server mode 18 minpoll 4 prefer   ?

> fudge flag1 1 flag2 0 flag3 1
This enables PPS on the NMEA ref clock.

You might try noselecting the NMEA / PPSes and gather data
 to try and get a fudge time1 PPS offset
 &/or a fudge time2 NMEA serial end of line offset.

> server it.pool.ntp.org iburst minpoll 10

 For testing with mroe sources, you might try changing that to:
pool it.pool.ntp.org iburst preempt minpoll 10
pool 0.freebsd.pool.ntp.org iburst preempt minpoll 10

> why server added (it.pool.ntp.org) is always considered as
> falseticker? Could be a remote (pool) server problem?

For the small number of sources you have, and their offsets,
 the single pool server is likely outside the intersection
 used to determine true chimers.

 You might also try increasing mindist, e.g.:
tos cohort 1 mindist 0.8

  How NTP Works

* Clock Select Algorithm

  Clock Cluster Algorithm

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