[time-nuts] US considers shutting down Loran

[Rob Kimberley]

>From my Austron days (and I'm sure technology may have moved a bit since
then), we always reckoned on about 1 microsecond as a fairly good accuracy
for a standalone LORAN-C timing receiver. 

Rob Kimberley 

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of John Ackermann N8UR
Sent: 20 January 2007 12:57
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] US considers shutting down Loran

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.

I recently got one of the (relatively rare) Austron 2100-T Loran receivers
that do timing; you basically lock the receiver to one of the periodic Loran
pulses that coincides with a UTC second marker and it generates a PPS signal
tracking that.  I haven't had a chance yet to run any long-term experiments
to measure its stability, but that's on my list of things to do.  (I also
plan to hook it up as a refclock for an NTP server; I'm not sure if there's
another Loran-based stratum 1 server out there today.)

John

John

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