[ntp:questions] Offset Average (Normal)?

David Lord snews at lordynet.org
Tue Mar 13 12:27:56 UTC 2012


David J Taylor wrote:
> 
> "Alby VA" <albyva at empire.org> wrote in message 
> news:7824f31d-b72c-44eb-9eeb-b219a7543db3 at gr6g2000vbb.googlegroups.com...
> []
>> ntp2.usno.navy. .USNO.           1 u  11h  128    0   21.392
>> 11.022   0.000
>> -ntp0.usno.navy. .USNO.           1 u  512  128  370   25.747
>> -0.242   3.378
>> +ntp1.usno.navy. .USNO.           1 u   51  128  377   30.361
>> -1.445   2.473
>> -time-a.nist.gov .ACTS.           1 u  136  128  336   19.894
>> 0.582   5.715
>> +time-b.nist.gov .ACTS.           1 u   64  128   57   19.100
>> -0.948   2.129
>> oPPS(0)          .PPS.            0 l   13   16  377    0.000
>> 0.502   0.153
>> *GPS_NMEA(0)     .GPSb.           0 l   12   16  377    0.000
>> -38.705  13.177
> 
> As Chris commented, you should maybe be using a single driver - here's 
> mine for a GPS 18 LVC (which should be similar apart from the baud rate):
> 
> ==============
> oGPS_NMEA(1)     .PPS.            0 l   16   16  377    0.000    0.004 
> 0.002
> +feenix          .PPS.            1 u   29   32  377    0.267   -0.027 
> 0.029
> +stamsund        .PPS.            1 u   13   32  377    0.246   -0.028 
> 0.035
> -time.hilo.net   130.88.212.143   3 u   67 1024  377   21.717    2.509 
> 1.349
> -server0.terrybu 140.203.204.77   2 u 1023 1024  377   23.783    3.814 
> 4.331
> +xinnaeus.bin.ed 129.215.64.32    2 u  677 1024  377   30.284    1.405 
> 0.739
> 
> and the configuration:
> 
> driftfile /var/db/ntp.drift
> #
> server  127.127.20.1    mode 0  minpoll 4 maxpoll 4  prefer
> fudge   127.127.20.1    flag1 1 flag3 1 refid PPS
> #
> server 0.uk.pool.ntp.org iburst minpoll 10 maxpoll 10
> server 1.uk.pool.ntp.org iburst minpoll 10 maxpoll 10
> server 2.uk.pool.ntp.org iburst minpoll 10 maxpoll 10
> #
> leapfile /root/ntp/leap-seconds.3535142400
> 
> (which has "just grown", so may not reflect current best practice).
> 



I've not noticed any significant difference after swapping to
use only NMEA driver as from March  2, 2012.

Also version of ntpd I was using in 2008/2009 didn't have nmea
driver with support for PPS.


NetBSD-5
Garmin 18X-LVC used from 2009 to March 2011.
Sure GPS used from March 2011 to date.
Serial cable length was extended by about 17m to confirm that
working over that distance would not be a problem.


Atom driver used from 2009
/etc/ntp.conf.11122702
#############
server  127.127.20.2  mode 18  prefer
fudge   127.127.20.2  time2 0.350  refid GPSb
server  127.127.22.2
fudge   127.127.22.2  flag2 0  flag3 1  refid GPSb
#############


peerstats.20120108
        ident     cnt     mean     rms      max     delay     dist     disp
==========================================================================
127.127.20.2    1350  -63.925   14.862   50.035    0.000    2.408    1.722
127.127.22.2    1350    0.000    0.003    0.030    0.000    0.928    0.928

loopstats.20120108
loop 1350, 7+/-24.0, rms 3.4, freq -35.89+/-0.159, var 0.078



/etc/ntp.conf.12030801
#############
server  127.127.20.2  mode 18
fudge   127.127.20.2  time2 0.410  flag1 1  flag2 0  flag3 1  refid GPSb
#############

peerstats.20120312
        ident     cnt     mean     rms      max     delay     dist     disp
==========================================================================
127.127.20.2    1350    0.000    0.003    0.028    0.000    0.928    0.928

loopstats.20120312
loop 1350, 3+/-25.1, rms 3.3, freq -35.13+/-0.204, var 0.054


David



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