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

Jean-Louis Oneto Jean-Louis.Oneto at obs-azur.fr
Thu Jul 1 19:49:03 EDT 2010


Hi,
If your GPS run in fixed position mode, how do you determine the position? 
Could this cycle be an artefact caused by a bad position? 50 mn could be the 
order magnitude of visibility of a satellite?
Just a thought...
HTH,
Regards,
Jean-Louis Oneto
----- Original Message ----- 
From: "David C. Partridge" <david.partridge at perdrix.co.uk>
To: "'Discussion of precise time and frequency measurement'" 
<time-nuts at febo.com>
Sent: Thursday, July 01, 2010 8:38 PM
Subject: Re: [time-nuts] Long period variation of GPS PPS timing?


> 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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