[time-nuts] Loran - any good for timekeeping?
John Ackermann N8UR
jra at febo.com
Fri Apr 21 16:05:50 EDT 2006
M. Warner Losh wrote:
> Can't you recover the time by tracking multiple chains and using the
> relationship between them to come up with at least small number of
> possible seconds? Hasn't the US started broadcasting data that can be
> used to know which second you are at?
I don't think that the US has started broadcasting a timecode, though I
think those plans are in the works.
I have to look at the Austron 2100T manual to get the exact sequence of
events, but basically you set the clock, feed an external PPS signal
that is roughly accurate (within some tens of milliseconds, I think),
and then enter the next time of coincidence (TOC) which you obtain from
the USNO (http://tycho.usno.navy.mil/lortoc.html). The TOC is when the
Loran pulse coincides with the UTC second. When the TOC rolls around
(which occurs a couple of times per day, the receiver locks to that and
you can remove the external PPS. From that point on, the PPS output
should track with the stability of the Loran signal unless/until it
Not sure about the idea of tracking multiple chains; it seems like that
should work, but that's not how the Austron receiver, at least, does it.
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