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Anatomy of a "signal generator":
Generally, "jammers" — which are also commonly called signal blockers, GPS jammers, cell phone jammers, wifi jammers, etc. are radio frequency transmitters that are designed to block, jam, or otherwise interfere with radio communications.
A jammer can block radio communications on devices that operates on a given radio frequencies within its range (i.e., within a certain distance of the jammer) by emitting a noise radio carrier. A GPS jammer generates a 1575.42 Mhz interference to prevent your GPS unit from receiving correct positioning signals. The GPS jammer is typically a small, self-contained, battery powered and transmit signal over a small radius. Though illegal to use, these low-tech devices can be bought on the internet for as little as $25. Since they can block devices that record a vehicle's movements, they're popular with truck drivers who don't want an electronic spy in their cabs. They can also block GPS-based road tolls that are levied via an on-board receiver. GPS jamming technology will also disable autopilot in drones to protect individuals' privacy.
In the US federal law prohibits the sale or use of a transmitter (e.g., a jammer) designed to block, jam, or interfere with wireless communications. For this reason some jammer retailers now label jammers as "signal generator kit" so it will just slip through customs and them is to purchaser sole responsibility for ensuring that the operation complies with the applicable laws. One of these "GPS signal generator kit" is the Dealextreme QH-1 Professional GPS Signal Generator Module (It seems that the QH-1 GPS jammer ran out of stock and will not be manufactured anymore, but you can still find HJ-3A GPS and cell phone jammer.). I've always wondered what's inside these jammers, given their cost, so i purchased one "signal generator module" and put under test with RF laboratory equiment, disassembled and photographed them for all to enjoy.
But is it cheaper than tinfoil?
[Ed note: typos and grammatical errors copied from source document, intact. Also note that it is illegal to operate one of these jammers in the US.]
(Score: 2, Insightful) by Anonymous Coward on Saturday December 02 2017, @08:21PM (2 children)
With respect to navigation systems (either driving aids or for autonomous navigation systems) it would be trivial to protect against this kind of interference using old tech and a bit of clever programming. First off the tech: inertial navigation systems have been around since World War II. While they aren't as accurate as modern day GPS, they are sufficiently accurate to prevent extremely large errors from cropping up (like being suddenly transported thousands of miles away) and to keep roughly on track for extended periods without GPS. Clever programming also makes this issue moot. We know that it is physically impossible for any vehicle to move thousands of miles in an instant. When this occurs the system should naturally ignore this spurious result and stick to the old data until a more reliable update is made. Combining either of these with modern sensor technology should protect against this and other forms of tampering. I can easily see future navigation systems, especially those used in autonomous transportation systems, including topographic data with resolution sufficient for a vehicle to know its location by a simple laser and optical scan of the area, comparing against its internal maps.
Also worth mentioning is that the british navy is working on a navigational system for their submarine fleet that uses the earth's magnetic field to locate itself. Last I read the device was about the size of a shoebox but that will be reduced eventually.
(Score: 0) by Anonymous Coward on Saturday December 02 2017, @08:39PM
Yes, of course inertial nav and other nav systems can fill in for missing GPS signals. Sometimes called "sensor fusion" there are test systems that combine GPS and inertial nav being used at automotive proving grounds, with centimeter accuracy.
But all this costs time and money to develop, so unless this is mandated for certain applications my guess is that it isn't happening anytime soon.
(Score: 4, Insightful) by frojack on Saturday December 02 2017, @08:50PM
Your average Passenger Car GPS is not funded by the British Navy.
These COTS GPS nav devices already know about bad signal area, mountains, tunnels, tall building canyon streets, etc and drop into some form of dead reckoning mode, and if they have a "can-bus" tie in, use vehicle speed as an input. They are already programmed not to panic in these areas.
That's entirely a different thing than suddenly, in the middle of a desert freeway, having only their built in magnetic compass to go by, seeing signals indicating location is 1000 mile away from where it was seconds ago, and having that new signal persist for some minutes.
Seems wrong headed to start building heroic measures into every car GPS beyond simply indicating to the driver that GPS is not available.
On the other hand, these jammers are not hard to detect, and that could be built into the freeway signage overheads. If we are going to have thousands of self driving cars and trucks out there it might be worth getting out ahead of this problem by at least installing some detectors to measure the size of the problem.
No, you are mistaken. I've always had this sig.