[time-nuts] 10MHz LTE-Lite - PPS accuracy?
docdailey at gmail.com
Mon Dec 8 09:25:54 EST 2014
Or use 1ns per foot of antenna cable. That will get you closer.
Sent from mobile
> On Dec 8, 2014, at 8:16 AM, David J Taylor <david-taylor at blueyonder.co.uk> wrote:
> 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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