[time-nuts] Trimble Resolution SMT GG weirdness

[Azelio Boriani]

Daniel,
a timing GPS receiver is not a GPSDO so its PPS is wandering about the
nominal position. Using a digital oscilloscope, I can see how much the
total wander is by activating the infinte persistence mode of the display.
After 10 minutes, 1 hour, 1 day or whatever you have an idea of the total
"coverage" of the wander. The trigger comes from a Z3815A reference. To see
the "dance" of the PPS coming from a GPS receiver, a simple crystal
oscillator as a reference is enough: use your microprocessor to generate a
PPS from its clock and visually compare this generated PPS with the GPS PPS
by a 'scope.


On Tue, Apr 23, 2013 at 7:49 AM, Daniel Ginsburg <dginsburg at gmail.com>wrote:

>
> On 23.04.2013, at 6:15, Hal Murray wrote:
>
> >
> >> I wonder, what kind of timing GPS gives 112ns wander?
> >
> > How good is your antenna?  112 ns is roughly 112 feet.  That's not at all
> > surprising if your antenna is inside or under trees.
> >
>
>
> Not perfect, but should be reasonably good. It's an external magnetic
> antenna on my windowsill.
> Anyway, +-400ns I'm seeing translates to +-120m in position. My surveyed
> location is better than this.
>
> > You might watch the number of satellites and/or watch the position while
> it
> > does a survey.
> >
>
> 6-10 SVs, with PDOP in range 1.6 - 3.9 (about 2.0 most of the time).
>
> >
> > --
> > These are my opinions.  I hate spam.
> >
> >
> >
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