[ntp:questions] Falseticking with PPS
unruh at invalid.ca
Tue Nov 22 21:32:31 UTC 2011
On 2011-11-22, Nickolay Orekhov <nowhere at mail.ru> wrote:
> Hello, all!
> I have the following configuration on my client:
> 1 PPS signal delivered from some GPS receiver and 1 NTP server
> Here's what I've got:
> QNX Neutrino (localhost) (ttyp0)
> ntpq> pe
> remote refid st t when poll reach delay offset
> xPPS(1) .PPSE. 0 l 5 8 377 0.000 -356.53
> x10.0.0.197 .GPS. 1 u 4 8 377 0.316 84647.8
> 10.0.0.198 .STEP. 16 u - 8 0 0.000 0.000
> Here's my config:
> tos mindist 0.032
> tinker panic 0 stepout 60
> # PPS reference clock
> server 127.127.22.1 maxpoll 3
> fudge 127.127.22.1 refid PPSE
> # External servers
> server 10.0.0.197 prefer iburst maxpoll 3
> server 10.0.0.198 iburst maxpoll 3
> Ok, I see, they are both falsetickers because of great difference between
> them. But why the difference is so great?
> I think the difference between PPS signal and some other signal can't be
> more than 1 second, isn't it?
PPS will give you accurate nanoseconds, but horrible seconds. Ie you in
general need something else to determine the seconds.
The more relevant question is why is 198 not working.
> May be I should increase tos mindist to be slightly greater than 1 second?
> Thanks, Nick
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