[time-nuts] Positional accuracy of the M12+T

Tom Van Baak tvb at leapsecond.com
Thu Jan 4 12:12:30 EST 2007

[ sorry, let me try that again ]

> Hmmm... with 25m position accuracy (and 100ns is
> about 30m), how do they really get time down to a
> few ns. Clever engineering!  :-)

You're comparing apples and oranges: accuracy and

The 25 m value you often read is probably a valid
figure for the positional accuracy of an M12.

But do not confuse this with the "few ns" timing value
you read about here. No one I know has an M12 that
is accurate to a few ns. What many of us have are
M12 that exhibit residual timing jitter of a few ns, when
properly sawtooth corrected and averaged over time
compared to a local cesium standard.

In other words, a properly filtered M12 is *stable* to a
few ns over some time frame. But it's highly unlikely it
is *accurate* to a few ns. A couple of ten ns is much
more likely. And this is in the same ballpark as the
"25 m" positional value.


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