[ntp:questions] question about logs of PPS

Christian Pinedo Zamalloa christian.pinedo.zamalloaNOSPAM at NOKKgmail.com
Tue May 15 07:48:26 UTC 2007

On 2007-05-09, Christian Pinedo Zamalloa 
<christian.pinedo.zamalloaNOSPAM at NOKKgmail.com> wrote:
> hi all,
> I'm a newbiew on NTP services, but anyway I'm trying to setup a Stratum1
> server with the following hardware and software:
> - GPS Motorola Oncore M12
> - Server:
>     - CentOS 3.8
>     - Linux kernel
>     - ntp 4.2.2p4
>     - PPSKit 2.1.7

After reading emails of the mailing list and searching the web i decided
to migrate the ntp server to FreeBSD 6.1. I enabled PPS_SYNC in the
kernel, compiled the kernel and the world, and configured again the ntp
daemon. The result is ok, the server is running better and it has
been announced as a stratum one public server in ntp.isc.org wiki.

Anyway, i would like to ask to the users of a Motorola M12 receiver what
should be the accuracy of the time server. Reading the logs and using
ntpq tool i see that is from several useg to hundred useg. I though that
it could reach nanoseg. Was I wrong?

$ ntpdc -c kern
pll offset:           -0.000101122 s
pll frequency:        -21.032 ppm
maximum error:        0.007368 s
estimated error:      3e-06 s
status:               2307  pll ppsfreq ppstime ppssignal ppsjitter nano
pll time constant:    4
precision:            1e-09 s
frequency tolerance:  496 ppm
pps frequency:        -21.032 ppm
pps stability:        0.645 ppm
pps jitter:           1.797e-06 s
calibration interval: 256 s
calibration cycles:   420
jitter exceeded:      3717
stability exceeded:   0
calibration errors:   27

Best regards,

Christian Pinedo Zamalloa

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