I'm sure this has been discussed many times here.
E-Loran - I designed the timing hardware that controlled the
transmitters for that upgrade while I was at Timing Solutions.
As I remember it, it was funded by the FAA to be a backup for GPS.
The FAA planned to make more use of GPS in the future (distant
future given the speed at which the FAA moves).
I'm not sure the Coast Guard was excited about the responsibility
of running LORAN.
Here is a powerpoint presentation arguing for e-loran:
https://www.gps.gov/governance/advisory/meetings/2009-05/doherty.pdf
Bob Martin
On 9/6/2018 4:35 PM, Scott McGrath wrote:
Actually we DID have a radio based system that provided sufficient accuracy it
was called eLORAN but it was killed by US politicians because they did not want
a much more inexpensive to operate system ‘competing’ with GPS. Shutting
down LORAN saved 32m dollars annually the NAVSTAR GPS program costs billions
annually.
Ironically while LORAN’s absolute accuracy is less than GPS, repeatability was
much better so fishermen liked LORAN better.
Once again the empty suits won and the navigation and timing community lost.
Wrt cellsites staying operational i imagine the oscillators in holdover would
probably remain sufficiently synchronized for a month or so.
On Sep 6, 2018, at 4:56 PM, Bob kb8tq <[email protected]> wrote:
Hi
Well, we *do* have experience with that. It was called selective availability.
Indeed it might get turned back on again. It’s impact on a properly designed
GPSDO - not much. It takes a bit longer to get to best stability. System time
wise, it still works “good enough”.
A four hour long test format also does basically nothing to a GPSDO based
system. You didn’t read anything in the papers about all cell service in three
states going away. The devices did what they are supposed to do and everything
did it’s boringly normal thing ….. it worked fine.
I still don’t quite understand just what people think could replace satellite
based timing in these systems. None of the “radio based” systems are within a
factor many thousands to a few million of being adequate.
=====
Now, if this is headed off into a “the government is coming to break down the
doors and take away all my toys sort of thing. That’s very much *not* a Time
Nuts topic.
Bob
On Sep 6, 2018, at 11:34 AM, Scott McGrath <[email protected]> wrote:
And there is the other significant vulnerability since GPS is a MILITARY system
the DoD can take it offline for any reason at any time.
Leaving civilian users with nothing,
If its a national security threat its likely the other GNSS systems will be
unavailable as well.
On Sep 6, 2018, at 9:53 AM, John Sloan <[email protected]> wrote:
Folks:
Well blow me down. It took some Google Maps fu on the web on my part, but
my time and place does indeed coincide with this “GPS Interference Testing” at
White Sands Missile Range. I just happened to be in my home office watching
several of my GPS-disciplined NTP servers when this occurred. Thanks, Graham!
:John
ZDV DENVER (ARTCC),CO. [Back to Top] !GPS 08/260 (KZDV A0287/18) ZDV NAV
GPS (WSMR GPS 18-20) (INCLUDING WAAS, GBAS, AND ADS-B) MAY NOT BE AVBL WI A
359NM RADIUS CENTERED AT 333345N1063840W (TCS054036) FL400-UNL, 311NM
RADIUS AT FL250, 215NM RADIUS AT 10000FT, 223NM RADIUS AT 4000FT AGL, 169NM
RADIUS AT 50FT AGL DLY 1830-2230 1809031830-1809082230
--
J. L. Sloan Digital Aggregates Corp.
+1 303 940 9064 (O) 3440 Youngfield St. #209
+1 303 489 5178 (M) Wheat Ridge CO 80033 USA
[email protected] http://www.diag.com <http://www.diag.com/>
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