Tom, Good points. I think that a lot of people are unaware of the diurnal shifts that occur due to atmospherics. These can be many 10's of nanoseconds compared to UTC. This is true for every receiver I have ever worked with. The ionospheric correction algorithms are good, but they are not perfect. Can't wait for a civilian L2.....................
Randy ________________________________________________________________________ ______________________________________ -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Tom Van Baak Sent: Thursday, January 04, 2007 9:13 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Positional accuracy of the M12+T [ 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 stability. 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. /tvb _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
