Posted on 09/17/2011 9:10:30 PM PDT by dickmc
“GPS receivers were quite purposefully designed to operate in a portion of the radio frequency spectrum deliberately maintained as a “quiet neighborhood,” with neighboring frequencies primarily occupied by signals of comparable power levels, all based on widely accepted understanding of previous FCC rules and intent. The proposed LightSquared transmitters will produce received signal strengths five billion times stronger than the GPS received signal.”
"Some have suggested GPS equipment can be redesigned for greater filtering to mitigate the interference, but even if this is possible, we believe it would involve substantial financial cost and likely degrade the accuracy of high performance receivers, which is critical to many key GPS users."
“We believe the signal strength proposed as 'lower power' is actually the same as in the originally published LightSquared plan—and was the power level upon which the NPEF (these) tests were based....”
“Emperical test results indicate the originally planned LightSquared network does not preserve existing GPS service in representative environments for most users.”
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The pdf of this Shelton testimony is at http://www.gpsworld.com/defense/shelton-testimony-12083
The link to the related GPS World article is here.
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(Excerpt) Read more at gpsworld.com ...
Any competent Electrical Engineer could tell you this plan was doomed to fail. The physics of how radio receivers work show that a powerful transmitter nearby would swamp/cover-up a weak signal source like a satellite transmission. Any ham radio operator could have told you this too.
So one of several things must be true.
1) The CEO of LightSquared didn’t listen to his engineers
2) He hired in-competent engineers.
3) He is stupid - which begs the question - how did all these other supposedly bright people put him in charge?
The Bush administration had their own version of this called Broadband over Power Lines. That technology in it’s initial implementation would have jammed HF signals across the world - and made the short-wave bands unusable.
The administrations get caught up in their own agendas and ignore physics, and practical engineering constraints. Don’t bother them with facts.
yeah - but you have to pass a test first to tell everyone where you are!
So, take into account the fact that many, many people own GPS units, and the fact that many of those units are truly portable (as in can be carried in your pocket and powered with AA batteries). I have a unit that sits on the dash of my truck that is of this type, and it is as accurate as those unit we had in militery usage 20 years ago (within about 3 feet using the WAAP satellites). Because it can be set for any type of usage (nautical, topo, highway, even aviation) it would represent a truly valuable tool in the event of any civil unrest in which a defender of the constitution might need to navigate without benefit of map, or might need to locate a specified target or cache.
Now... Consider the fact that we know that Washington has the power to shut down landline comms, internet, cell comms, and to some extent radio comms (even that can be eliminated over time through triangulation and arrest of the operator of said equipment, or via jamming)... Why wouldn't Washington welcome the idea of being able to shut down and/or interfere with GPS? Sort of a "The peasants are on the rise? Call up LightSquared and tell them to max out the power... We can't have the commoners going cross country on us- they might get around a checkpoint..."
For those that know how to use one properly, a GPS can perform an awesome amount of tasks. Have at it folks, but let's keep it grounded on earth and leave the alien abductors out of it, okay? :-)
Please excuse the typos... Big thumbs on a little, tiny phone’s keyboard!
last month without a whimper don’t ask don’t tell was repealed by Obama without any regard to military effectivness.
Obama does not give a rat’s posterior about the military.
you don’t need GPS if you are only on government approved crony capitalism mass transit systems.
Um, didn't the FCC assign the spectrum that Lightsquared proposes to use?
” Why wouldn’t Washington welcome the idea of being able to shut down and/or interfere with GPS?”
They can. They can turn off the civilian channels within seconds. They can even change the resolution to be a mile off if they wanted.
How is LTE on the 700MHz spectrum “doomed to fail?” Verizon Wireless has introduced it in over 100 cities. Now, it’s clear they are taking a more cautious approach to their deployment - Buffalo, for example, has not been activated due to interference from analog TV channels from Canada.
Thus, while I agree with (probably) all three of your points, I don’t agree with your conclusion, that it’s a plan doomed to fail.
They really aren’t the same thing.
A TV signal isn’t weak compared to a GPS satellite signal. It’s an apples and oranges argument you’re making (If I understand it correctly..) Further, TV’s do have some level of filtering, though as an amateur radio operator, i would argue even that isn’t sufficient.
What is going on here is that they are putting KW transmitters within Mhz of what was always intended to be a quiet zone spectrally speaking. There is no front-end protection against adjacent signals within GPS receivers. Lightsquared is bitching about that - but they weren’t required to put that front-end rejection in because of the service it is operating in, i.e. a satellite service with the expectation of no strong near neighbours.
On my home station if I enable positional ambiguity, my coordinates place me right in the middle of the regional airport. The TSA must be going crazy trying to find the ham operator out on the tarmac. LOL.
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