[ntp:questions] clockvar output from PPS

Dave Hart hart at ntp.org
Wed Feb 22 00:18:11 UTC 2012


On Tue, Feb 21, 2012 at 18:57, Alby VA <albyva at empire.org> wrote:
>
> Dave
>
>  Fixing my Sure GPS wiring/soldering and correcting my ntp.conf file,
> this is now what I'm showing:
>
> # ntp.conf  - snippit
> #
> server  ntp.alaska.edu          minpoll 7 maxpoll 10 iburst
> #
> server 127.127.20.0 mode 18 minpoll 4  maxpoll 4 prefer
> fudge  127.127.20.0 time2 0.350 refid GPSb
> #
>
>
>
> godzilla#
> godzilla# ntpq -p
>     remote           refid      st t when poll reach   delay
> offset  jitter
> ==============================================================================
>  ntp.alaska.edu  .GPS.            1 u   87  128    1  121.513
> 13.436   6.009
> *GPS_NMEA(0)     .GPSb.           0 l   95 16 40 0.000
> -33.725   0.002
> godzilla#
> godzilla#
> godzilla#
>
>
>
>  But after a few short minutes of jumping up and down with joy, I run
> another
> ntpq -p query and I see this (See Below).  My reach has gone to zero,
> I still
> have an offset, and NTP has switched from GPS_NMEA to
> ntp.alaska.edu ..
>
>
>
> godzilla#
> godzilla#
> godzilla# ntpq -p
>     remote           refid      st t when poll reach   delay
> offset  jitter
> ==============================================================================
> *ntp.alaska.edu  .GPS.            1 u   50  128 17 121.284
> 29.879  12.571
>  GPS_NMEA(0)     .GPSb.           0 l  453   16    0    0.000
> -33.725   0.000
> godzilla#
> godzilla#

Your configuration is using the NMEA end of sentence timing alone.
Assuming you want to use PPS, you need another piece.  Either remove
prefer from 127.127.20.0 and add flag1 1 to its fudge line (which will
enable integrated NMEA+PPS operation), or add a separate PPS driver
with "server 127.127.22.0 minpoll 4".

I'm not sure why the reach went to zero on GPS_NMEA(0).  Running ntpd
interactively with -dd (or -D2) might give a hint.

Cheers,
Dave Hart


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