[time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)

[David I. Emery]

On Sun, Nov 15, 2009 at 10:33:07PM -0500, David I. Emery wrote:
> 
> 	LORAN C represents a viable (albeit not often deployed) backup
> to time and frequency control and could be implemented in modern
> hardware as a backup location service at reasonably low cost for those
> applications where that is important enough.	

	I might add that there ARE some regional solutions to the timing
and frequency backup issue (time-nuts meat) that COULD be implemented
pretty easily. 

	One is locking ATSC TV signals to Cs standards backed by GPS. I
am pretty sure that it would not take a lot of effort to adopt existing
ATSC Tuner chip designs and maybe the actual current technology already
available  chips themselves to recover accurate time and frequency from
a ATSC signal locked to a good standard.

	And TV transmitters are LOUD compared to GPS and therefor not so
easily jammed on a wide area basis.
	
	I don't imagine the cost of Cs locking a few TV signals is all
that high either... most of the gear can accept external frequency
references and clocks... and already does to a considerable degree.

	Obviously if one needs time of day to high precision one needs
to use a local GPS to determine the time offset of a TV signal as
received at a particular site, but this should not change much provided
the clock at the transmitter was really good.   And the ATSC transport
stream provides a rich channel for sending information about time offsets
and other sync status on a real time basis... 

	I suppose this could substitute for Loran as a regional backup
for telecoms networks as protection against GPS denial...

-- 
  Dave Emery N1PRE/AE, die at dieconsulting.com  DIE Consulting, Weston, Mass 02493
"An empty zombie mind with a forlorn barely readable weatherbeaten
'For Rent' sign still vainly flapping outside on the weed encrusted pole - in 
celebration of what could have been, but wasn't and is not to be now either."