[time-nuts] Timing between two GPS PPS outputs.

[David J Taylor]

From: Gabs Ricalde
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Non-timing receivers could be unsuitable for your requirements, as
some of us have discovered:
http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html#oscillations
[]
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Gabs,

The oscillations I reported are not due to the use of a navigation GPS 
receiver.  Three things lead me to that conclusion:

1 - the magnitude of the offsets is far greater than would be expected from 
the specifications of the navigation receivers.

2 - I replaced the U-blox NEO-6M with a unit based on the MTK3339 module, 
but the oscillations continued with visually the same amplitude and 
frequency.

3 - I replaced the MKT3339 module with a unit based on the U-blox LEA-6T 
timing GPS, but the oscillations continued with visually the same amplitude 
and frequency.

[The one obvious difference between the two Raspberry Pi cards is that the 
one without oscillations is begin fed with USB data into its USB port, 
although that data isn't used by NTP, with gpsd not even running on that PC, 
whereas the problem PC has nothing in the USB port.  However, while writing 
this note, I recall that one of the PCs has X enabled and the other does 
not, so better try disabling X as putting a memory stick in the USB port 
hasn't made any difference.]

Cheers,
David
-- 
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-taylor at blueyonder.co.uk