Equipped to Survive Foundation has joined the newly formed Coalition to Save Our GPS, which is opposed to the unusual and unsound waiver by the FCC for LightSquared to use its satellite spectrum for high-powered ground-based broadband transmissions that may interfere with GPS signals before testing has determined that it is safe to do so.

Read about the Coalition to Save Our GPS and what you can do to help: http://www.equipped.org/blog/?p=317

That sounds like such a NOT good idea. You got my attention.

HJ

Thanks for the heads up on this -- just sent an e-mail to the FCC as the Save Our GPS website suggested. They have an impressive list of backers; hopefully someone in D.C. notices the 800-pound gorilla in the room.

How could they not consider this beforehand? Isnt GPS a Military based Thing first and foremost? Doesnt the military rely on GPS For almost everything including artillery these days?

Just follow the money and politics...

I asked someone whose been out of the military for a while now and he said that the GPS they use is completely different from the GPS you and I use. They have their own separate set of satellites, different frequency, etc that has replaced the system we use. He couldn't give many more details since that was classified.

Interesting I never knew that. I originally learned GPS was Military only with civilians able to use it but with major distance error readings on purpose by the government till Bill clinton opened it to us. I wonder when they replaced Their system?

Not exactly...........

The US military uses standard GPS. They used to use Selective Availability to encrypt part of the signal to reduce civilian GPS precision, but that's been discontinued.

I have no way to verify that and he said he can't give me any details but they were using the new stuff already when he was still in. Part of his job was putting the gps receivers and radios in military vehicles, setting up the encryption keys and such so I would think he knows whats hes talking about.

http://www.saveourgps.org/Testimony_of_Jim_Kirkland.aspx



Oops, looks like the folks at FCC really haven't got much of a clue when it comes to Out of Band frequency performance of Chinese made Circulators and Isolators (to be used in the Lightsquared cellular network) etc.

The frequency domain performance of these devices is only as good as the calibration of the Microwave Network Analyser at the factory and the mechanical/thermal stability of the rubber cement/ceramic squirted under/into the terminals of these devices by the Chinaman sitting in front of the Analyser.

Thanks for the heads up Doug.

Blake

www.outdoorquest.biz

My understanding is that military GPS uses two separate signals sent on two separate frequencies. One of those signals is encrypted.

Civilian GPS uses only the un-encrypted signal.


In the atmosphere, the signal will follow a path that deviates somewhat from a straight line. That deviation is somewhat different for those two frequencies. Comparing the two can give you much better accuracy than just using one channel. It also has the added benefit that you can deliberately reduce the accuracy of the civilian GPS without affecting the military GPS.


The deviation from a straight line in our atmosphere is the main cause of GPS inaccuracy. Systems as WAAS and EGNOS works by transmitting additional information about that deviation. WAAS/EGNOS enhances the accuracy of a civilian GPS from about 10 meters (30') to about 1.5 meters (5').

So - no separate military GPS satelites, but a separate military frequency that is used together with the "free-for-all" civilian frequency.

Maybe thats what he meant then, when he installed the gps receiver is was a separate system on a separate frequency and they don't use the civilian gps.

DOT, DOD LETTER VOICING CONCERN ON POTENTIAL THREAT TO GPS

http://www.equipped.org/DepSecDef_DepSec DOT Letter_Signed.pdf

Link to DOD, DOT slam FCC over GPS interference concerns

YouTube on the GPS-LightSquared Issue at New 4G Network Could Cripple GPS Navigation.

The LightSquare product has a potential for disrupting the GPS signal.

Below is a link for one test of the product. It will be for the aviation sector in the Las Vegas/Los Angeles area. I'm sure others will be affected also. We'll see...

https://www.faasafety.gov/files/notices/2011/May/LSQ-LAS_Flight_Advisory.pdf

This video is no longer available because the YouTube account associated with this video has been terminated due to multiple third-party notifications of copyright infringement from claimants including:
Discovery Communications
NBC Universal
Discovery Communications

First responders are reporting GPS location issues with the testing of LightSquared's system. Included is a highly technical progress report by LightSquared to the FCC.

LightSquared Testing Update

The LightSquared executives must have been scratching their heads...LOL.

http://www.gpsworld.com/gnss-system/first-responders-lightsquared-issue-11620

The Holloman AFB test would no doubt have had the very best cherry picked out of band performance isolators for that test to get past the FCC ( look it works no problemo ). Must of been a considerable temperature difference between the factory when the isolators were tuned and at Holloman AFB that day. As the rubber RTV cement holding the ceramic contracts and expands in the isolator the tuning performance esp the out of band performance will vary considerably. GPS only has a signal strength of around -120 to -140 dB on the surface of the earth.

Edit - Nope it looks like the LightSquared Execs have figured that one out by running the field tests during the night when temperatures are much cooler and match the factory where the isolators were tuned.

Doug,

Has there been any more news on this issue?

I am seeing where LightSquared is beginning to pick-up steam with providers, and several tower companies are staffing up for the future build-out.

This tells me to expect expanded deployment in the near future.

Lots going on, momentum building against Lightsquared, including from DOD finally, which carries significant weight, but lots of politics, of course. No clear idea how it will turn out, but more optimistic than I was.

LightSquared has changed their approach. RF is certainly not in my bag of tricks. Changing their frequency... with little provided technical data, is that enough? Or is it just smoke and mirrors?

And what prevents them from quietly migrating to the original freq at a later date? Yes, playing devil's advocate.

LightSquared changes spectrum to avoid GPS interference

Update: powerful committee says there's no way to mitigate LightSquared's GPS spectrum interference. Without an(other) extraordinary political intervention, looks like they're sunk.

Couldn't happen to a nicer bunch.

That's a relief. Thanks for the update, Glock-A-Roo!

Apparently they're not so nice. Here's a link to a story where LightSquared blames everybody else.

Having personally run a number of sensitive testing programs for the federal government I can tell you it would be way beyond the norm for LS's accusations to be true. While the govt. often relies on independent industry test organizations like mine (because of both subject matter knowledge and testing expertise) they also make sure tests are run aboveboard. One test doesn't make a career so folks have incentive to get it right. Ask Doug Ritter, he's done a few himself.

Update: "FCC moves to kill LightSquared over GPS interference concerns"

Killed for now BUT eventually people will want to use those frequencies for something and unless the GPS providers start adding filters or otherwise ensuring they aren't susceptible to interference of some sort this will catch up to them (and the consumers) eventually.