[ntp:questions] Realistic Performance Expectation for GPS PPS fed ntpd jitter

David J Taylor davidtaylor at writeme.com
Thu Oct 8 10:09:38 UTC 2020


Hello,

I wonder what's a realistic ballpark for the jitter I can expect when
feeding a GPS PPS into ntpd?
[]
Thanks, regards
Andreas
=======================================

Andreas,

I have some offset plots here:

  https://www.satsignal.eu/mrtg/performance_ntp.php

and a few experimental clock and system jitter plots here:

  https://www.satsignal.eu/mrtg/performance_ntp_jitter.php

For an unloaded Raspberry Pi, 1-4 us, for an RPi carrying out another task
perhaps as high as 5-7 us for an RPi zero.  For a Windows-10 PC 4-50 us
depending on load and CPU speed and age.  All given a reasonably clear
satellite view, and no GPS jammer truck parked outside!

[us => microsecond]

Cheers,
David
--
SatSignal Software - Quality software for you
Web: https://www.satsignal.eu
Email: david-taylor at blueyonder.co.uk
Twitter: @gm8arv



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