[time-nuts] Long period variation of GPS PPS timing?
vlf0308 at abelian.org
Thu Jul 1 12:06:54 EDT 2010
Thanks all for the various replies, on and off list.
John WA4WDL wrote:
> Perhaps you should use only the leading edges for the
> pulse-to-pulse interval measurement.
Yes, I'm just using the leading edge, turning it into a pulse
using a couple of RC networks, slowing the rise and fall enough
to give a nice shape for accurate locating of the centroid.
Antonio CT1TE wrote:
> I can send you the yesterday record of my GPS TBolt #2 against
> DCF77, which apparently doesn't show any periodic phase
Thanks for the offer. Hold on that, I'll assume for now that
this slow cycle is not ionospheric.
Rob Kimberley wrote:
> I'm assuming your location is fixed, and you are tracking
> sufficient SVs,
Fixed. Maybe I can relocate the GPS antenna for a better view of
Peter Vince wrote:
> I don't believe that cyclic variability is GPS - I've not
> noticed such a thing on any of the systems I monitor.
Thanks, that's very helpful. Knowing that this is not normal
behaviour for GPS timing means that I can set about tracking down
a system fault.
There are a few things I can think of to check. The cycle must
correlate with something - soundcard rate, temperature, CPU clock,
etc. It is pretty consistent, here is a bit more of MSF 60kHz
and also DCF at 77.5kHz,
Thanks again, I'll report back when I find the problem.
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