[time-nuts] US considers shutting down Loran

[M. Warner Losh]

In message: <45B21199.3060901 at febo.com>
            John Ackermann N8UR <jra at febo.com> writes:
: Hal Murray said the following on 01/19/2007 11:12 PM:
: > From http://www.fcw.com/article97298-01-08-07-Web
: > 
: >> Norman said the Alliance for Telecommunications Industry Solutions
: >> (ATIS), whose membership includes all the telecom carriers in the
: >> country and equipment vendors, views eLoran as the "only viable
: >> alternative to GPS for providing [Coordinated Universal Time] of day
: >> and frequency accuracy that is suitable for a telecom primary
: >> reference source."
: > 
: > How good is Loran for timing?  What's the right parameter for "good"?
: 
: When used for frequency measurement, Loran is good to parts in
: 10e-13/day -- ie, not much worse than GPS.  Of course, that's referenced
: to the Cesium clock at the Loran station, so you need to do a little
: juggling to trace back to NIST.  I believe that as they enhance the
: stations to the new hardware, the discrepancy from NIST will be much less.

The new loran timing systems use 3 High performance Cs that have been
steered to GPS.  The delta between the GPS receiver and the master Cs
is on the order of nanoseconds.  The current Loran data messages can
be used to recover UTC (since it contains the number of leap seconds
necessary to reconstruct UTC from the raw loran GRI clocks).

Warner