[time-nuts] Long period variation of GPS PPS timing?

Paul Nicholson vlf0308 at abelian.org
Wed Jul 14 03:41:12 UTC 2010


Just a follow-up on this.

Yesterday I received a Thunderbolt from fluke.l,

  http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=290322053618

This worked straight away and has cured the 50 minute drift
cycle.  I'm getting a standard deviation of pulse interval of
about 0.25uS, as measured against the soundcard sample clock.
It ought to be a bit better than this, but the 10uS PPS width
is a bit too short for a steady timing of centroid through a
soundcard at 192k samples/sec, I need to stretch the pulse a
factor of 10 or so.  The Thunderbolt seems to take about 45 mins
to settle down to a steady rate, which is fine.

Meanwhile, Garmin wrote to say they will try to reproduce
the 50 minute drift on the GPS16X.

So that problem is fixed.  Thanks for the advice and suggestions.
-- 
Paul Nicholson
http://abelian.org
--




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