[ntp:questions] Re: Is the time from the GPS receiver bad ?

Richard B. Gilbert rgilbert88 at comcast.net
Sun Sep 10 23:52:34 UTC 2006


Eugen COCA wrote:
>>From time to time the ntpq -pe output from my servers looks like this:
> 
>      remote           refid      st t when poll reach   delay   offset
> jitter
> ==============================================================================
> +GPS_NMEA(1)     .GPS.            0 l   52   64  377    0.000    0.000
>  0.004
>  ptbtime1.ptb.de .PTB.            1 u   75  256  377  155.060  -48.458
> 35.782
>  ntps1-1.cs.tu-b .PPS.            1 u   91  256  377  151.487  -47.099
>  1.731
>  ntp-p1.obspm.fr .1PPS.           1 u   11  256  377  123.504  -22.762
> 19.197
>  gps-2.mit.edu   .GPS.            1 u   34  256  377  246.793  -49.433
>  3.131
> oPPS(1)          .PPS.            0 l    4   16  377    0.000    0.000
>  0.004
>  ptbtime2.ptb.de .PTB.            1 u   38  256  377  157.004  -47.865
>  2.205
>  gps-1.mit.edu   .GPS.            1 u   24  256  377  239.559  -38.903
> 31.765
> 
> The question is: is it the time received from the GPS receiver bad ? I
> suppose a network problem (upstream delay different from downstream
> delay) but how may I bypass this problem - for the moment I have the
> noselect for all external servers (without the noselect option the
> server will reject the time from the GPS receiver).
> 
> Thanks !
> 

  If the outgoing and incoming delays are not symmetric, an error will 
be introduced.   The size of your offsets suggests that this might be 
the case.  The delay figures for all your internet servers seem 
unreasonably large!  Can you not use servers nearer to your site?




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