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Engineers Build Satellite Jammer
cencini writes: "According to this article, U.S. engineers developed a device for $7,500 which generated UHF signals strong enough to jam mobile GPS systems. My question is, couldn't you build something like that for less?!" Update: 04/20 02:42 by H : The folks at New Scientist wrote with the original article - the device actually blocks UHF signals, but can be modified for other bands.
Everytime I take off a few days from my demanding job in the Valley, I like to head off to places like Yosimite and Yellowstone. But each month it seems that there are more and more untrained yuppies, grinding up the roads with their SUVs, displaying their designer hiking outfits (Tommy Hilfiger backpacks, anyone), and *always* carrying a GPS.
Granted, most of them have no idea how to actually *use* a GPS, or how to coordinate it with a map, but a few manage to figure it out if they haven't succumbed to heat stroke after the first mile or so (apparently they believe that there are Starbucks's scattered every 100 feet, just like in Manhattan). Having conquered the navigation system, they feel supremely condfident, and stride forward in their fashionable Donna Karan outdoorwear. But just sit back, and in a few hours, after wandering a few yards off the path, those newbies will be crying for help, and they expect the rangers to spend their time to go off and rescue them! How absurd! It is the *user's* job to be prepared, not the staff. Why won't they learn? The last thing we need is to devote our time, as a community, to digging these helpless newbies out of a trench they've buried themselves in. If you want to enter *our* territory, you better do it on *our* rules, pal.
I have this friend that has a navagation system in his truck. It's a nice system, between the GPS and a CD map of the east coast he is able to get just about anywhere.
But he uses it to get everywhere. He punches in the address for the grocery store (a mile away) and then punches in the address for back home. Maybe the novelty of a $3000 toy wears off slowly, maybe he is really that bad with directions.
For some reason the thought of wacked-out luddite guerrillas jamming his satellite signal on his way home from the corner market really cracks me up. I can just see him driving aimlessly for hours waiting for the navigation system to tell him when to turn.
Man-oh-man, a GPS jammer is a toy that may not lose it's novelty for a while....
RF jamming is hardly a new technology, and the people who came up with GPS aren't stupid. This possibility has without a doubt already been considered and dealt with - give them a little credit here. Jamming a spread-spectrum carrier means using a broadband jammer, which is expensive, sucks a lot of power, generates tons of heat, and has a paltry range. Even a theater-based GPS jammer would be inconcievable; barring a massive technological investment, at most only a small portion of the theater could be jammed (realistically). Also, neither smart bombs nor cruise missiles are solely reliant on GPS.
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I think there is a world market for maybe five personal web logs.
[it is] believed that the latest generation of global communications satellites would be immune to similar home-built equipment, as they are "heroically resistant to jamming"
What does Heroically Resistant mean? I can see this satellite in orbit straining: must resist jamming! grr!It must be wonderful to be so naive that you trust technology to be heroic.
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GPS contains the following capabilities:
Selective Availability adds some noise to the signal received by civilian receivers; military receivers can tune this one out using a specific cryptographic key. Selective Availability was actually turned off during Desert Storm, because the U.S. military didn't have enough "military" receivers for their troops!
Anti-Spoofing makes it cryptographically impossible to give a bogus signal to a military receiver.
The P code (P for Precision) gives very high precision to certain military receivers which have been equipped with receivers for the P code signal, in addition to the regular (CA, for Coarse Aquisition) code. The P code is not receivable by civilian receivers.
The GPS signal is jam resistant by being spread spectrum, but as the poster points out, there isn't any defense against wideband ("barrage") jamming.
The GPS signal coming from the sattelite has a deliberate offset so that they are never 100% accurate. This is because any moron with a steerable missile (rockets can't be steered, missiles can) that can carry a nuclear bomb can wire up a GPS as a precision-guidance system to deliver this missile very accurately.
In time of war, the offset increases dramatically, though supposedly that didn't happen during Desert Storm. I think it has something to do with the GPS capabilities of the enemy.
The military GPS was designed with anti-spoofing (just like IP spoofing) and anti-jamming (I think it dynamically changes frequencies, but not sure) capabilities, but these are not built into the civilian models.
The military GPS can be given a cryptological key that significantly increases the accuracy and enables all the other Electronics Counter-Countermeasures (ECCM--Electonic Countermeasures, or ECM, is what normal people call jamming, ECCM is what you do to combat ECM).
Of course, once you start barrage jamming (blocking out the entire radio spectrum), all bets are off. Nothing can make it through barrage jamming.
I do what the voices on my console tell me to do.