[ntp:questions] High jitter with GPS Clock

Rickan Lee rickan2000 at hotmail.com
Tue Nov 11 08:49:57 UTC 2003


Hi all,

I have connected a GPS-Clock (Acutime 2000) via phone wire to my PC. (Linux
2.4.20-8, ntpd 4.1.1c).

However, what I don't understand is the jitter is very high.

[root at linux]# ntpq -p
     remote           refid      st t when poll reach   delay   offset
jitter
============================================================================
==
*GPS_PALISADE(0) .GPS.            1 l   30   32  376    0.000    7.369
9.381
+ntp1.ptb.de     .PTB.            1 u   44   64  377   18.836   29.007
1.644

When I run ntptrace at the command line I get:
----------------------------------------------------------------
[root at linux]# ntptrace -v
server 127.0.0.1, port 123
stratum 2, precision -16, leap 00
refid 127.127.29.0 delay 0.00111, dispersion 0.00000 offset 0.000442
rootdelay 0.00000, rootdispersion 0.00465, synch dist 0.00465
reference time:      c35b1f26.0bb352a8  Tue, Nov 11 2003  9:41:10.045
originate timestamp: c35b1f33.fcc36da8  Tue, Nov 11 2003  9:41:23.987
transmit timestamp:  c35b1f33.fc7b352a  Tue, Nov 11 2003  9:41:23.986
----------------------------------------------------------------------------
------

What could be wrong? I have a simple config as follows:
----------------------------------------------------------------------
server 127.127.29.0     prefer            # Trimble acutime 2000
fudge  127.127.29.0 stratum 1
fudge  127.127.29.0 time1 0.020
fudge  127.127.29.0 flag2 1

server 192.53.103.103

driftfile /etc/ntp/drift
broadcastdelay  0.008

logfile   /var/log/ntp          # alternate log file
----------------------------------------------------------------------------
---------

And I think the jitter should be very low since I have a local GPS clock.
But as you can see above that is not the case.

I would be very appreciative for any hints.







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