[time-nuts] GPS for ntp

David J Taylor david-taylor at blueyonder.co.uk
Tue Oct 21 05:07:03 EDT 2014

From: Simon Marsh

No claims are any good without being backed by data, so attached are a
couple of plots showing my NTP performance from the past 4 hours.
'Sheliak' is the BBB with the PCI-5S and 'Albali' is a Pi with an
adafruit ultimate GPS breakout (MTK3339). It's easy to see the heating
coming on at ~6:20, as both servers are out in the open and it's
interesting to see how they both respond to the temperature change. The
scale is in milliseconds, so 5m is showing 5us.


.. and for comparison, plots from seven Raspberry Pi NTP servers running 
various GPS/PPS modules all with indoor antennas, some better located than 
others.  Raspberry Pi #7 is user-mode PPS, not kernel-mode.  I can supply 
loopstats if anyone want them.

These are the offset values reported by NTP and sampled by MRTG at 5-minute 

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Email: david-taylor at blueyonder.co.uk 

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