[Pool] High Offset / Jitter

Alby alby at empire.org
Tue Mar 1 03:18:51 UTC 2011


David:

 Thanks. I threw your suggestion into ntp.conf and it appears to
be doing better. Although I had to modify the time1 from 0.651 to 0.850.
I still might tweak that, but for now GPS_NMEA is the favorite
in my list and hasn't changed since it sync'd.

NOTES:
======
godzilla:/etc# ntpq  -p
     remote           refid      st t when poll reach   delay   offset 
jitter
==============================================================================
-time.nist.gov   .ACTS.           1 u   13  256  377   55.940   33.040  
7.125
-ntp-nasa.arc.na .GPS.            1 u   21  256  377   91.018   37.884  
5.590
-tick.usask.ca   .GPS.            1 u   12  256  377   90.859   34.895  
4.456
-ntp.alaska.edu  .GPS.            1 u    9  256  373  131.397   31.648  
5.831
+timekeeper.isi. .GPS.            1 u    5  256  377   88.070   29.832  
6.597
+ntp2.usno.navy. .USNO.           1 u    7  256  377   68.397   26.230  
5.577
*GPS_NMEA(0)     .GPSb.           0 l    -   64  377    0.000   17.842 
12.029
 PPS(0)          .PPSb.           0 l    -   16    0    0.000    0.000  
0.001
godzilla:/etc#





On Mon, February 28, 2011 7:32 pm, David Lord wrote:
>
> I used "tos mindist 0.4" to overcome the problem with my
> 18x-LVC and version of ntp I was using on NetBSD.
>
>
> Without that line ntpd tries to lock to GPS serial data
> and then is out of range for PPS so coninuously flips between the two. I've
> not tried GPS with a more recent ntp which is supposed to better handle
> this situation.
>
> Of course the 18x might be too far out. I had a brief
> look on the Garmin site but could only find the current firmware. My unit
> was purchased mid 2009 and has not been updated.
>
> It's possible I was using serial or parallel pps at the
> time but there was no significant difference when using serial DCD.
>
> $ ntpq -p
> remote       refid st t poll reach delay offset jitter
> ===========================================================
> +GPS_NMEA(0) .GPSb.      0 l   64  377  0.000 -7.687 13.108
> oPPS(0)      .PPSb.      0 l   16  377  0.000  0.000  0.002 - -k6x400
> 192.168.??  2 u   64  377  0.619  0.785  0.631
> +me6000gi    .MSFa.      1 u   64  377  0.722  0.905  0.519
> - -p4x2400c     92.168.??  2 u   64  377  0.774  0.690  0.381
>
>
> *************************
> # /etc/ntp.conf:
>
>
> tos             mindist 0.4
>
> server 127.127.20.0 mode 1 prefer minpoll 6 maxpoll 8 fudge  127.127.20.0
> time1 0.651 refid GPSb
>
> server 127.127.22.0 minpoll 4 maxpoll 6 fudge  127.127.22.0 refid PPSb
> flag3 1
>
> server k6x400     minpoll 6 maxpoll 8 server me6000g    minpoll 6 maxpoll
> 8
> server p4x2400c   minpoll 6 maxpoll 8 *************************
>
>
> David
>
>
> - --
> David Lord <david at lordynet.org>
> <ftp://ftp.lordynet.org/pub/pgpkeys/lg_david.pkr>
> <http://www.lordynet.org/pub/pgpkeys/lg_david.pkr>
>
>
>
>
> -----BEGIN PGP SIGNATURE-----
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>
>
> iQA/AwUBTWw+oa2RmIodDo7KEQL5rgCgoUYzMdKGi8qc+QE7T1TDYsALjN0AoPO9
> OhdgZwrvs/FjFvA8CVMmu+/w
> =/bjz
> -----END PGP SIGNATURE-----
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