[time-nuts] Training period for a Rb clock using GPS

Robert Benward rbenward at verizon.net
Wed Jun 2 02:48:35 UTC 2010


The microprocessor "learns" the drift of the oscillator while it is connected, so that when GPS is lost, it can make 
those corrections in anticipation of drift.  The longer it's locked to GPS, the better  it learns the drift (more 
history).  Don't confuse the word drift with "locked", even when locked, the oscillator is drifting and continuously 
being corrected.  These corrections (the voltage to the EFC or electronic frequency correction) are an indication of the 
oscillator drift, even though the output is exactly 10MHz.

Others can provide links to useful articles.


----- Original Message ----- 
From: "Abhay Parekh" <parekh at berkeley.edu>
To: "Discussion of precise time and frequency measurement" <time-nuts at febo.com>
Sent: Tuesday, June 01, 2010 10:36 PM
Subject: [time-nuts] Training period for a Rb clock using GPS

> Hello,
> I am a newbie at this, but have been playing around with 2 prs10s.
> For our application we need to run the clocks without gps, but we do get to
> sync it to gps *initially* for as long as we want.
> However, what we've noticed is that when we train it for short periods of
> time
> (< 1 hour a day) the clock drifts for a few microseconds a day once we've
> disconnected
> gps, but when we train it for say 12 hours, its drift seems to be much less
> (sub sub microsecond/day).
> We were wondering why this should be so! I apologize if this is obvious to
> most of you but
> I would greatly appreciate your help in shedding some light for us.
> Thanks!
> =Abhay
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