[ntp:questions] PPS from an external OCXO source. Correcting drift is it possible?
maarten at kittensandcats.net
Fri May 1 17:57:25 UTC 2009
"Kat" <Schwar3Kat at gmail.com> wrote in message
news:c5391c04-b342-4922-b520-ff862fa3802c at v1g2000prd.googlegroups.com...
<homebuilt OCXO PPS>
> I have two problems with it. 1. It starts off with a random offset.
You can fudge that in the configuration file. It's a common problem
with an easy solution.
> 2. The offset drifts at about 20 milliseconds a day.
You can't fudge that as far as I know. Perhaps the expectation is
that PPS signals are generally much better - this is 2.3e-10 which
sounds rather good until you realise it's 20 ms each day.
How far are you willing to go? You might be able to build a clock
based on the PPS that is amenable to disciplining through NTP, but
if it's only for holdover during Internet outages, perhaps you'd
be more helped with a way to keep the offset down (or at least
known) between Internet outages.
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