[ntp:questions] high jitter on serial gps causes big time offsets

Nickolay Orekhov nowhere at mail.ru
Fri Apr 5 11:09:29 UTC 2013

I've got the following configuration:

tos mindist 0.128
tinker panic 0 stepout 60

# TSIP,PPS reference clock

server mode 10 prefer maxpoll 3 true
fudge refid TSIP time1 0.08

server maxpoll 3
fudge refid PPSI

The main goal: I want 1 ms or better precision always, even with gps
quality going high and low.

When satellites appear and disappear again, serial clock could be selected
before PPS clock. Or maybe some gps receivers will show good quality before
PPS will appear or will be selected.

In general, I want ntpd to skip adjustments coming from specific server or
ref clock according to some constant precision. For example, I know that
gps serial jitter is about 30-40 ms. So I want ntpd to do no adjustments
lower than this value. And when PPS will appear it will be selected.

Can this be done? Or how do you solve this situation?

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