Why is my 1PPS GPS stratum-0 clock always ~100ms behind other ntp servers?

by Jeff Mixon   Last Updated October 28, 2017 07:00 AM

I am trying to set up a stratum-1 time server. I have a Navisys GR-701 GPS which is capable sending a 1 PPS signal. According to the spec sheet and sources such as this, I am under the impression I should obtain ~1ms accuracy with ntpd. However, my ntpq output always looks similar to the following:

$ ntpq -c pe
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
xPPS(0)          .PPS.            0 l    5   16  377    0.000   -0.603   0.144
oGPS_NMEA(0)     .GPS.            0 l    6   16  377    0.000   -0.600   0.143
 us.pool.ntp.org .POOL.          16 p    -   64    0    0.000    0.000   0.000
 pool.ntp.org    .POOL.          16 p    -   64    0    0.000    0.000   0.000
 time-b-b.nist.g .NIST.           1 u   66   64  377   40.537  103.278   0.370
 209.208.79.69   130.207.244.240  2 u   64   64  377   81.895  107.050   1.926
 time.tritn.com  66.220.9.122     2 u   58   64  377   19.908  102.778   1.410
 ns3.clickspace. 142.66.101.13    2 u   67   64  377   77.661  103.662   2.634
 time-a.nist.gov .NIST.           1 u   55   64  377   84.697  101.964   1.898
 four0.fairy.mat 128.227.205.3    2 u   54   64  377   75.199  103.477   1.648
 linode.appus.or 216.218.254.202  2 u   55   64  377   13.440  103.428   3.977
 chimera.buffero 128.252.19.1     2 u    7   64  377   51.236  103.062   4.075
 ha82.smatwebdes 199.249.223.123  2 u   57   64  177   62.222  101.612   1.638
 ns1.backplanedn 129.6.15.30      2 u   55   64   77   78.225  105.745   4.298
 li290-38.member 128.138.141.172  2 u   51   64   37   58.979   99.250   6.847
 christensenplac 209.51.161.238   2 u  115   64   36   83.498  103.723   6.923
 ada.selinc.com  .PPS.            1 u   80   64   32   42.069  102.975   3.238
 linode.ibendit. 199.102.46.77    2 u   87   64   36   55.966  100.589   1.802
 96.226.123.195  128.138.141.172  2 u   13   64   37   51.370   90.311   1.714
 clock.sjc.he.ne .CDMA.           1 u   41   64   17   12.778  103.102   0.351

Is ntpd really saying my clock is ~100ms "behind" every other clock? If so, why is is so and what can I do about it?

Tags : ntp ntpd


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