[time-nuts] I've been thinking about a GPS receiver experiment

Magnus Danielson magnus at rubidium.dyndns.org
Tue Oct 24 22:56:07 UTC 2017


I would rather use the rich Novatel reports and read out the time error 
and use that as your phase detector, then the normal PI-loop stuff with 
an optional low-pass to add and then use that to steer the rubidium.

It's one of those, when I get time, projects.


On 10/25/2017 12:17 AM, Skip Withrow wrote:
> Hello time-nuts,
> I've been thinking about a GPS receiver experiment and just wondering
> if there are any opinions or prior experience that might save me a lot
> of time.
> What I have been thinking about doing is taking a GPS receiver
> (Novatel OEM4-G2) that has provisions for an external clock (5 or 10
> MHz) and driving it with a rubidium oscillator (that has 1pps
> disciplining, (such as the X72 v5.05 or SRS PRS-10).  The GPS even has
> settings for OCXO/rubidium/cesium dynamics.
> Then, (and here is the unknown part) what if the GPS receiver 1pps is
> used to discipline the rubidium?  This basically forms a feedback
> loop, so could either hurt or help - depending.  Supposedly the better
> oscillator would give a better GPS solution.  And the better solution
> (1pps) should provide a better oscillator frequency.
> We know that GPS receivers using asynchronous clocks have 1pps errors
> and hanging bridges (OEM4 is spec'd at 20ns rms), If the oscillator is
> on 10MHz and disciplined will the 1pps error be reduced such as the
> Thunderbolt?
> Comments appreciated.
> Regards,
> Skip Withrow
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