[ntp:questions] Very large jitter and offsets on GPS ref clock after upgrade to "p5"
David J Taylor
david-taylor at blueyonder.co.uk.invalid
Wed Feb 8 17:45:09 UTC 2012
"David Lord" <snews at lordynet.org> wrote in message
news:gnbbu8-qne.ln1 at me6000g.home.lordynet.org...
> I've not put a scope on the pps but I added an extra section
> of cable from my Sure GPS, 18 m of 4 x pair telephone cable.
> I will need that length to reach from the GPS down to my PCs.
> In the process the offset jumped from 0.004ms to about 12ms
> but fairly quickly went back to a few usec.
> PC = me6000 (VIA ME6000), NetBSD-5, ntpd 4.2.6p5
> From my ntp-stat file:
> time offset(ms)
> 15:06 -0.004
> 15:12 0.000
> 15:18 0.001
> 18:24 0.006 extra 18 m cable added
> 15:30 -12.938
> 15:36 -3.672
> 15:42 -0.814
> 15:48 -0.186
> 15:54 -0.054
> 16:00 -0.012
> 16:06 -0.006
> 16:12 -0.002
> 16:18 -0.002
> 16:24 -0.001
I suspect that the offset jump was purely from losing the PPS signal, and
nothing to do with the extra cable as such. BTW: I think your editing
accidentally included the time - from 15:24 to 18:24. Must have had "18"
on the brain! <G>
My comments on wiring are as before - use one line from each pair as
ground, and then the other four "active" lines become TXD RXD PPS and +5V
More information about the questions