[time-nuts] 10MHz LTE-Lite - PPS accuracy?
David J Taylor
david-taylor at blueyonder.co.uk
Mon Dec 8 09:16:18 EST 2014
On *most* GPSDO’s, the simple answer is “there is a cable delay adjustment
to align it”. Without some sort of reliable representation of UTC (at the ns
level) it’s tough to measure. If you happen to live at USNO or NIST, you can
access that sort of timing. For the rest of us - not so easy. The NIST two
way GPS “modem” setup is about the only practical method that I know of.
The PPS out of any GPSDO will be much lower jitter than the pps from a
normal GPS module.
Thanks for your comments. The antenna location and cable lengths are very
similar (either 0, 5m or 10m) so I was expecting somewhat less than 50 ns
difference. 200+ ns is rather more than I expected for the LTE-Lite, so I
did wonder whether anyone else had measured it.
Although I've not checked it rigorously, most of the GPS/PPS units here of
various brands are within under 100 ns of each other, hence my expectation.
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Email: david-taylor at blueyonder.co.uk
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