[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 09:08:37 UTC 2009
> I use cat 5e cable since it is cheap, available and is supposed to be
> good for better than about 100MMHz
> (10nsec) signals. I would not use usb cable or any old wire, because
> the problems of spread of the pulse from the gps. Also I would
> it properly as well so that signal reflections could be problematic.
> long runs.
> If the run is less than 10m it should be ok even with improper
Cat 5e cable sounds like a good compromise. On very long runs, you would
not only need to terminate the cable correctly, you would need to drive it
correctly as well, requiring powered line drivers and receivers at either
In the OP's case, the run is only 30m (i.e. about 100-150ns) so the effect
of reflections on a system (RS-232) which is bandwidth-limited to a
microsecond or two should be very little, and I would likely use the cable
in an unbalanced configuration.
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