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

David C. Partridge david.partridge at perdrix.co.uk
Thu Jul 1 16:38:18 EDT 2010


Sawtooth variation in pps time - that does sound a bit familiar in reference to GPS timing.

e.g.: <http://www.leapsecond.com/pages/m12/sawtooth.htm>  but that's over a MUCH shorter time scale than you report which seems to a around 3000 seconds.

So I wouldn't write it off as being unrelated to the GPS quite yet, but I admit I can't think of an obvious candidate with this sort of period.

Regards,
David Partridge


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of Paul Nicholson
Sent: 01 July 2010 19:44
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Long period variation of GPS PPS timing?

FYI, some time has elapsed with one soundcard instead of two and the slow cycle is still present, same period, and the phase of the slow cycle did not make a step change.

Now I must take a careful look at how the centroid is being determined, the resampling, RC temperature, etc.
Maybe the 'sawtoothness' of the cycle should be telling me something.  If nothing jumps out at me, I'll change the rise/fall time constants of the RC network and see if that alters the slow cycle.
--
Paul Nicholson
http://abelian.org
--

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