[ntp:questions] Slow convergence of NTP with GPS/PPS

David J Taylor david-taylor at blueyonder.neither-this-part.nor-this-bit.co.uk
Fri Oct 24 06:36:04 UTC 2008


Unruh wrote:
[]
> With a minpoll of 4, just setting the phase correctly with zero drift
> compensation would at worst be out by 1ms by the next reading. And
> you can get a pretty good estimate of the drift, even if it is
> changing. The temp coefficient is not 10PPM/degree C. More like 1 or
> less. That means the first few measurements gives a pretty good
> estimate of the drift ( ie to a few PPM) and then the finer
> corrections can come while things settle down.

It isn't NTP which is the limit, but the GPS receiver acquiring lock from 
scratch after an indeterminate period of being switched off.  The GPS 
could take minutes to lock and declare that it has valid time.

David 





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