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

Skip Withrow skip.withrow at gmail.com
Tue Oct 24 18:17:46 EDT 2017

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

Comments appreciated.

Skip Withrow

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