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posted by martyb on Saturday December 02 2017, @06:30PM   Printer-friendly
from the we-be-jammin' dept.

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.]


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  • (Score: 1, Interesting) by Anonymous Coward on Saturday December 02 2017, @07:54PM (10 children)

    by Anonymous Coward on Saturday December 02 2017, @07:54PM (#604377)

    The J bus knows. It controls the truck. It can tell you are in drive and the engine is going and the odometer is increasing. That gets 99% of movement. You could probably follow the angle of the wheels from steering and actually trace it back out on a map. Would be tricky to get right but it should work.

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  • (Score: 3, Interesting) by frojack on Saturday December 02 2017, @08:27PM (7 children)

    by frojack (1554) on Saturday December 02 2017, @08:27PM (#604382) Journal

    Depends on who's truck it is. Lots of time all you actually have access to is the trailer or your merchandise in the trailer.

    Besides, building a INS seems the hard way.

    There are plenty of AM and FM radio and Digital TV towers scattered all over the country that are fairly easy to RDF or triangulate with nothing more than signal strength. Chipsets are already available for all of these, and you need only record relative strengths every X minutes for post trip analysis, or to phone home with a cheap cell modem a few time a day.

    --
    No, you are mistaken. I've always had this sig.
    • (Score: 2) by KilroySmith on Saturday December 02 2017, @09:37PM (6 children)

      by KilroySmith (2113) on Saturday December 02 2017, @09:37PM (#604407)

      So you're suggesting that the solution to someone jamming GPS RF signals...is to listen to cellphone RF signals?
      And when the jammers become GPS+Cellphone jammers, listen in on TV signals?
      And when the jammers become GPS+Cellphone+TV jammers, listen in on AM signals?

      When does it end?

      • (Score: 1) by Ethanol-fueled on Sunday December 03 2017, @01:20AM

        by Ethanol-fueled (2792) on Sunday December 03 2017, @01:20AM (#604500) Homepage

        Where does it end? Either directly integrated in the road, or better, my solution -- a hybrid rail/car system which combines the best of both worlds of safety, privacy and independence, and uniformity of traffic flow. As others have mentioned ad-nauseum, some kind of dual-or triple-factor system should be used with ultimate accuracy. I would suggest rather than an INS a 3-beam doppler sensor aimed down the bottom of the vehicle directly at the road. The main advantage of this would be extreme accuracy and granularity of measuring the exact arc and direction of turns as well as velocity on all surfaces. It would not be susceptible to jamming and ability to compensate for uneven height of surfaces (up down hills, even while turning, speed-bumps etc) in such technology has been well-understood for decades.

        Of course, if it is too accurate (as it should be) the gubmint will get involved because Muh Terrorism and cripple it to the point of being useless or ITAR-regulate it. Not that Europe would want it anyway, they seem to be having a lot of truck-related problems lately.

      • (Score: 2) by VLM on Sunday December 03 2017, @02:33AM (3 children)

        by VLM (445) Subscriber Badge on Sunday December 03 2017, @02:33AM (#604527)

        Use aircraft VOR navigation and ILS beacons and when you jam them the FAA with F-22s will show up.

        • (Score: 1) by Ethanol-fueled on Sunday December 03 2017, @04:27AM (2 children)

          by Ethanol-fueled (2792) on Sunday December 03 2017, @04:27AM (#604568) Homepage

          I always like what you have to say, but haphazardly throwing around a bunch of military terminology in this case makes you look like a hammer treating every solution as a nail.

          Our situation needs to be a little more intimate to the problem at hand. We're way passed TACAN on the ground, we just don't know it yet. I switched majors because chemistry nomenclature was inconsistent. I was in Chem 101 when I learned that the only way forward was to memorize through brute force the nomenclature of mono and polyatomic ions. -ates and -ites are -2 or -3 depending, as one example.

          So I decided that I should go back to my exact science of electronics. But then I barfed, because it has the same problem: microwaves have longer wavelengths than millimeter waves. You would think that microwaves would have shorter wavelengths than millimeter waves, but you would be wrong. Microwaves go up to 30 GHz, even though micro is smaller than milli, but millimeter waves are from 30 GHz up to the hundreds of GHz.

          • (Score: 2) by Aiwendil on Sunday December 03 2017, @12:23PM

            by Aiwendil (531) on Sunday December 03 2017, @12:23PM (#604625) Journal

            So - you are annoyed at that they used the word "micro" in the sense small (which is what the word actually means) and decided to use "milli-" in the sense "1 to 10mm long"?

            I'm curious: when armed with ca 1930s knowledge what name would you have chosed for waves smaller than what is currently in practice to use? [parvwave? paulwave? petitwave?]) (if anything - you should be annoyed that it stops at the mm band and not just keeps going ad infinition (maybe renaming the "microwave" band to the centiwave band))

            Personally I'm annoyed at that "small" (micro) is used as a word for something specific to begin with - so in part I share your annoyance - but it could have been worse, they could have called them "dwarf-waves" (nano-)

          • (Score: 2) by VLM on Monday December 04 2017, @01:03PM

            by VLM (445) Subscriber Badge on Monday December 04 2017, @01:03PM (#605005)

            So I decided that I should go back to my exact science of electronics. But then I barfed, because it has the same problem

            You're lucky you got out before they inflicted the WWII era secret radar band designation on you and today people still talk about S band vs X band which is about 5 ghz higher and the other ten or so WWII radar bands. That designation system is really annoying. Even outside radar / ECM, like people call big dish satellite TV "C band" vs the "K band".

            My favorite inconsistent metric problem is I've met normies who kinda understand centimeters from being taught CGS at school and then they take the "its all about the 100x" to everything and its possible to get into interesting arguments with people about ping times where they'll insist a 100 ms ping time is 1 second because 100 centimeters is 1 meter.

      • (Score: 2) by frojack on Sunday December 03 2017, @03:00AM

        by frojack (1554) on Sunday December 03 2017, @03:00AM (#604538) Journal

        I'm suggesting to the AC who recommended building an initial navigation system into the trucks j bus, that his method wouldn't work, or would be too costly, whereas something the size of a cell phone can fulfill the tracking needs of major shippers sending valuable cargo over the highways using contract truckers.

        This would have been clear if you had bothered to follow the thread instead of rushing in to but words in my mouth.

        --
        No, you are mistaken. I've always had this sig.
  • (Score: 4, Interesting) by edIII on Saturday December 02 2017, @10:06PM (1 child)

    by edIII (791) on Saturday December 02 2017, @10:06PM (#604422)

    You could probably follow the angle of the wheels from steering and actually trace it back out on a map.

    There used to be a system that did rely *only* on the movement of the wheels, angle of the tires, etc. I was in this guys car in Los Angeles back in 1988-1990 (IIRC), and he showed me his guidance system. It did indeed show where we were, and our next steps on an amber screen mounted on the dash. Overtime it lost its accuracy, but it could keep it going for about days use. He told me that he needed to calibrate it almost daily. Started at the very beginning of his street, getting out of the car to be sure. You drove about a half a mile and then input your location again. After that the system was calibrated and knew where your vehicle was.

    It was really cool at the time, but even he acknowledged it was too expensive and impractical. Just bought it to geek out. I'm fairly certain they only had accurate maps for Los Angeles and a few other cities. He never said it worked well out of the city. That, and it was amazing you could retrofit a car with that much computing power back then.

    --
    Technically, lunchtime is at any moment. It's just a wave function.
    • (Score: 2) by VLM on Sunday December 03 2017, @02:32AM

      by VLM (445) Subscriber Badge on Sunday December 03 2017, @02:32AM (#604526)

      Navicom?

      http://7car.tw/articles/read/12512 [7car.tw]

      The pictures don't look like what I remember.

      In the 80s/90s I was interested in TSD rallys for the novelty and sheer technological challenge and curta calculators and all that stuff, then cheap GPS rolls out and the sport turns into a mode on the GPS, essentially. But, before GPS, there was COOL stuff out there.