[time-nuts] M12+ Site Survey

Attila Kinali attila at kinali.ch
Tue Mar 24 16:48:00 EDT 2015

On Tue, 24 Mar 2015 19:52:30 -0000
"Martyn Smith" <martyn at ptsyst.com> wrote:

> If I then move the unit, for example 30 miles and leave it in position hold (without doing another site survey)
> How will the accuracy of the 1 pps pulse be affected?
> In this instance, I don’t actually care about alignment to UTC.
> I’m just worried about the accuracy of the 1 pps pulse and ultimately the
> accuracy of my rubidium’s frequency.

I think you mean "precision" and not "accuracy"[1] :-)

If you leave the module in position hold and the module does not realize
itself it has been moved, then the PPS will be very jittery. How much,
I cannot tell (I have not seen any data of extreme off positions like that).
I would guess several ms. But it would be still a pulse roughly every second.

Poul-Henning had some experience with "a bit off" position with his M12
due to high solar activity (I've seen it on his webpage, but cannot find
it at the moment). He used (uses?) an algorithm with which the receiver
can "creep" up to its actual position over time[2].

If you move around often, i would simply disable position-hold and live
with "normal" GPS precision, which is better than 100ns for most receivers
and good sky view.


			Attila Kinali

[1] http://en.wikipedia.org/wiki/Accuracy_and_precision 
[2] http://phk.freebsd.dk/raga/sneak/

< _av500_> phd is easy
< _av500_> getting dsl is hard

More information about the time-nuts mailing list