[ntp:questions] NMEA ref.clock better than my ISP's timeserver?

David J Taylor david-taylor at blueyonder.not-this-part.nor-this.co.uk.invalid
Fri Jun 12 08:59:38 UTC 2009

Unruh wrote:
> The nmea is virtually useless for accurate timing. The main thing that
> the unit gives you is the PPS. You have to makes sure you do not
> degrade it.

The GPS 18x LVC only claims an accuracy of one microsecond for PPS in the 
first place.  The RS-232 receivers may well have some filtering limiting 
the risetime to a couple of microseconds (i.e. good enough for the maximum 
baud rate, typically 115,200 baud), so even if the final risetime after 
the cable is a microsoecond or so, that's not going to degrade the 
accuracy signifcantly for normal use.  Not an issue.

>>> I'm not sure whether the NMEA driver attempts to send anything /to/
>>> the
> Which NMEA driver?

The one in NTP, which would work with the GPS 18x LVC.


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