[ntp:questions] Sure gps looses all sattelite fixes

David J Taylor david-taylor at blueyonder.co.uk.invalid
Fri Feb 24 18:26:48 UTC 2012

"unruh" <unruh at invalid.ca> wrote in message 
news:cmQ1r.3572$py5.2962 at newsfe09.iad...
> The graphs of the signal strengths at the edges of these dropouts is in
> ftp://theory.physics.ubc.ca/outgoing/drop{out,in}.pdf

Could not access this page in Firefox.

> Is this a flaw in the Sure unit (NOte that the sure unit drops its PPS
> signal as soon as it does not a fix. Some units-- Garmin?-- keep sending
> out PPS based on the freerunning onboard clock for quite a while, as I 
> understand it.
> Teh Sure does not, which may be an advantage or a disadvantage.
> (ntpd/chrony grab one of the other servers which produces
> discontinuities in time when the pps comes back)
> Is it evidence of some outside noise source (jamming?) , microwave tower
> emission?

That's certainly a possibility.  I would try to locate the antenna so that 
it has a clear view of at least half the sky, preferably towards the 
south.  You may also notice seasonal effects with foliage blocking the 
signal more in spring and summer.

Mine have a moderate view of the sky, being located indoors, but on the 
top floor of a domestic residence.  Both pucks are stuck (magnetically) on 
top of a PC, which does form a ground plane, but may also be a source of 
electrical noise!  I haven't monitored as you have, but I suspect I see 
the effects of a drop-out perhaps once a fortnight.


More information about the questions mailing list