[time-nuts] carrier phase tracking GPS receiver
Didier Juges
didier at cox.net
Mon Feb 19 20:43:53 EST 2007
Hi Bruce,
Dr Bruce Griffiths wrote:
> Bon soir Didier
>
> You are confusing the disciplining precision of the oscillator with
> measurement of its short term stability via the GPS receiver in this case.
>
> Bruce
>
>
Bon après midi to you, I believe, and if my Clock program is any good,
you just had lunch :-) Do you have Daylight Savings Time?
Yes, I realize that I am very confused, but at the end of the day, the
two have to come together. It does me little good to know how much off
my oscillator was, some time in the past. That information has to be
available in time to steer the oscillator, in real time, because what I
am looking for is a precise oscillator, not a history lesson (like the
BIPM view of UTC, where it takes a month for the paperwork to be
processed so that everyone knowns by how much they were off last month :-)
You said:
Typically with a good local oscillator you can do even better than that,
around 1E-11 in 1 sec is achievable and has been achieved.
Even with the on board TCXO typically 3E-11 or so in 1s is achieved.
Is this 3E-11 1) measured on the 1 PPS output, 2) measured on the TCXO,
or 3) the interpretation, by external computing of the carrier phase
data, of the quality of the timing prediction from the GPS receiver?
If it is 3), how can I use that information to make a 3E-11 @ 1sec (or
anything near that) stable GPSDO?
I think I am beginning to understand, but it's slow coming...
Didier
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