[ntp:questions] Ultralink 325 WWVB receiver

Dennis Hilberg, Jr. timekeeper at dennishilberg.com.invalid
Mon Feb 11 18:56:22 UTC 2008


Dennis Hilberg, Jr. wrote:
> I'll generate some plots and post links to them in a few days, after 
> enough data has been gathered.  I probably should have done that from 
> the beginning.

I set up a machine (janus) specifically to monitor the offset of the machine 
running the wwvb receiver (apollo) as compared to my server running the GPS 
(saturn).  Janus's only two synchronization sources are apollo and saturn, 
of which saturn is flagged as a truechimer to avoid janus jumping between 
the two sources, as happened in the beginning, which threw the measurements 
off.  Janus polls saturn and apollo at minpoll 4 in order to follow them as 
closely as possible.

Anyway, I've gathered plenty of data, and I can clearly see the stepping 
behavior I described before in the 24 hour pll offset plot.  Interestingly 
though, viewing the seven day "offset as viewed from janus" plot shows a 
regular but much larger swing +-40 ms.  Notice also the swings in the seven 
day frequency graph mimic the swing intervals on the "offset as viewed from 
janus" plot.

Here are the plots:
http://saturn.dennishilberg.com/ntpstats/rrdtool/apollo.php

I really don't know what to make of the data, so any help would be appreciated.

Thanks.

-- 
Dennis Hilberg, Jr.     \  timekeeper(at)dennishilberg(dot)com
NTP Server Information:  \  http://saturn.dennishilberg.com/ntp.php




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