[ntp:questions] best gps receiver for time synchronization
"terje.mathisen at tmsw.no" at ntp.org
Wed Mar 11 09:33:12 UTC 2009
Martin Burnicki wrote:
> Agreed, too. However, if we are discussing about Garmins with 50 ns accuracy
> then 1000 ns delay is magnitudes worse.
Garmins never give better than about 1000 ns, i.e. 1 us.
> Also, PPS pulses must not necessarily be used only as PPS signals for
> computers. We have also applications where just a piece of hardware is
> synchronized by a PPS signal, in which case 1 microsecond *is* relevant.
The gold standard seems to be the Oncore timing receivers, they give you
a PPS signal accurate to 100 ns: This is the best they _can_ do since
the PPS signal has to be synchronized to an edge of the internal 10 MHz
For use with NTP we do much better however, since the Oncore knows
exactly how far off the PPS signal is from the true point, and this info
si sent as part of the serial port signal (the "sawtooth correction"),
giving a real measured accuracy in the 15-35 ns range, depending upon
- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"
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