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From: Brooke Clarke (no email)
Date: Wed Jun 08 2005 - 21:51:15 EDT
Hi Courtney:
On the contrary, they will continue to work as they did, maybe better
performance because of the improvements in the antennas, transmitters
and the reference timing sources.
But remember that LORAN-C was originally designed for coastal navigation
and now the focus is on blind aircraft landing. So the coverage area
does not extend too far from any coast. Global coverage map:
http://www.locusinc.com/images/MegapulseMap1.gif
But I expect the coverage area to increase, especially near major airports.
I have a number of timing LORAN-C receivers and they are almost as good
as GPS, see: http://www.pacificsites.com/~brooke/A2100F.shtml
Have Fun,
Brooke Clarke, N6GCE
Courtney Thomas wrote:
> Does this mean our old Loran receivers are soon worthless, or still
> usable just not as accurate, or what ?
>
> Thank you,
> Courtney
>
>
> On Wed, 2005-06-08 at 16:19, Brooke Clarke wrote:
>
>>Hi Carl:
>>
>>The current LORAN-C system is made up of chains of stations, one master
>>and a hand full of slaves. Now the slaves listen for the master pulse
>>and after a wait send their pulse. In the not too distant future all
>>stations will just transmit based on a collection of Cesium clocks.
>>
>>The result will be a more accurate fix.
>>
>>The older LORAN-C receivers could needed to be programmed for the Group
>>Repetition Interval (GRI) of the nearest chain. The new generation
>>receivers are, to borrow a GPS term, "All In View". These receivers
>>know about all the world's stations and use Digital Signal Processing
>>technology to receive all the stations at the same time.
>>
>>It was not only the events on 9/11 but also the realization that it's so
>>easy to jam GPS and European and Russian counterparts that kept LORAN-C
>>alive.
>>
>>The U.S. has turned off Selective Availability which makes a GPS fix
>>more accurate for civilian users, but to counter this the military is
>>developing jamming technology and from time to time tests it. If you
>>happen to be in a test area you position will be either wrong or non
>>existent.
>>
>>Have Fun,
>>
>>Brooke Clarke, N6GCE
>>--
>>w/Java http://www.PRC68.com
>>w/o Java http://www.pacificsites.com/~brooke/PRC68COM.shtml
>>http://www.precisionclock.com
>>
>>
>>
>>Carl Herzog wrote:
>>
>>>Lu Abel wrote:
>>>
>>>
>>>>Two or three years
>>>>ago the US Coast Guard was trying to accelerate their schedule for
>>>>shutting down Loran C. Now it looks like they and the US Department of
>>>>Transportation (which includes the US's Federal Aviation Administration)
>>>>are concerned about possible problems with GPS in navigation
>>>>applications (such as aircraft routing or precision harbor approaches)
>>>>that require hyper-reliability and appear to be considering an enhanced
>>>>Loran as a backup system.
>>>
>>>
>>>As of 1992, plans were in place to eliminate LORAN by 2015. By 1994, the
>>>termination date had been bumped up to the year 2000. Opposition by
>>>LORAN users, largely lead by general aviation interests, caused another
>>>review of the need for the system.
>>>
>>>At the same time, in an unrelated effort, the Volpe National
>>>Transportation Systems Center, a division of the U.S. Dept. of
>>>Transportation, was studying the vulnerabilities of the GPS system. They
>>>released their resulting paper on September 10, 2001. This report is
>>>available as a pdf online:
>>>
>>>http://www.navcen.uscg.gov/archive/2001/Oct/FinalReport-v4.6.pdf
>>>
>>>Needless to say, the events the next day gave the report a higher
>>>profile than it may have otherwise had.
>>>
>>>It was shortly after that the department began looking at refurbishing
>>>the existing LORAN infrastructure to backup GPS. Upgrades to the LORAN
>>>infrastructure in the U.S. are already well underway. This spring the
>>>Coast Guard upgraded all the transmitters and new timing and frequency
>>>equipment is being installed this summer.
>>>
>>>Studies are still underway to determine whether an enhanced LORAN system
>>>can completely meet standards for accuracy and other characteristics
>>>that would be required for it to serve as a backup to GPS in aviation
>>>and harbor approach navigation. So far the results look promising, but
>>>it may be a few more years before you start seeing integrated GPS/LORAN
>>>receivers for sale at your local marine supply store.
>>>
>>>Carl
>>>
>>>
>>>
>
>
>
>
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