Any competent electronics enthusiast, technician or engineer should be able to build the jamming electronics device from parts costing a few hundred dollars.
A hostile party operating a wide-range GPS jammer on a congested multi-lane expressway could enjoy an attractive disruption pay-off. The simple power density formula used does not take into account radiation power losses due to humidity water vapour or rainfall in the air, but the argument for the asymmetrical appeal of a wide-range GPS jamming attack is nevertheless undeniable.
Instead of a fibreglass-bodied cube van, a smaller metal-bodied trades van could have its dual rear windows tinted, to disguise a pair of rearwards-facing parabolic antennas. A smaller vehicle could carry a battery with storage capacity of 9kWh, giving three hours of jammer operation at 3kW power. The antennas could be disguised as roof racks, or hidden inside a plastic cargo or ski box mounted on roof racks. The hostile party unleashing a series of newsworthy, widespread GPS jamming attacks on urbanites would vividly demonstrate the vulnerability of this technology.
There is a great deal of anger on social media at the moment, and the ranks of the disaffected are growing. A small conspiracy of such people could easily develop GPS jammers and deploy them at randomly-selected times and locations, garnering a satisfying media frenzy.
It is not easy to pinpoint the source of a GPS jamming attack. Defenders need sophisticated equipment for location by triangulation. Mobility of jamming equipment complicates tracking, as does the brevity of a jamming session. A small team of roaming GPS jammers, rotating through a pseudo-random jamming schedule, will increase the interdiction challenge.
Then alarms sounded. The radar did the same. Last deliberately simulated a simple, commercially available jammer. They can also block GPS-based road tolls that are levied via an on-board receiver.
Some criminals use them to beat trackers inside stolen cargo. It is not known how many are out there, but the panel is concerned that the risk of interference is growing fast. An event last year at Newark Liberty International Airport in New Jersey showed that it only takes one jammer to cause disruption.
Airport controllers had installed a new GPS-based landing system, so that aircraft could approach in bad visibility. But it was shutting itself down once or twice a day. It took several months to find the culprit: a driver on the nearby New Jersey Turnpike using a portable GPS jammer to avoid paying the highway toll. This trucker was cruising past twice a day, crippling an airport as he went. GPS is also increasingly relied upon for guiding emergency services to the scene.
It is estimated that more that a billion GPS receivers are now in operation, he says, and more than 90 per cent use the signals only for the accurate time provided by the satellites. Cellphones are a key user of this invisible utility. Towers must synchronise with each other to pass calls to other towers as you move — a GPS time signal offers a cheap and accurate way to do this.
The timing offset for each tower is also used to identify it. In fact, many wireless communication technologies use GPS timing for synchronisation. GPS timing can time-stamp financial transactions , such as stock-market trading. And ATMs sometimes communicate wirelessly, using a time-based encrypted code that requires synchronisation.
Though it is not known why the cash machines stopped working during the San Diego event, this might have something to do with it. Energy suppliers use GPS time to keep alternating current from various power plants in phase across the grid. If frequency cycles are not matched, two supplies will partially cancel each other out, creating inefficiency.
When this occurs, the GPS device is unable to determine its position due to interference. The relatively low power and quick start up time allow the jammers to be used only when required. To understand how a jammer functions, it is also helpful to know how the global positioning system GPS works.
A GPS tracker receives microwave signals from an array of satellite transmitters orbiting the Earth. Once the tracker receives signals from four or more satellites, it determines its position through a series of time calculations and trilateration. The receiver relies on these precise and specific satellite signals to determine where it is in the world.
The GPS tracking device then transmits this position and velocity information to a monitoring location, usually, sent over the cellular network. In some cases, satellite malfunction or solar flares can temporarily disrupt the transmission of GPS signals.
A GPS jammer is different though in that it sends out radio signals or signal noise with the same frequency as the GPS device, to override or distort the GPS satellite signals. When this occurs, the GPS device can then no longer calculate its position because the satellite signal is masked by the interference. The reasons for using jammers are varied. Originally created by the government, GPS jammers were designed for military use.
Concealing vehicle location can be crucial to the success of a mission. The devices act as a cloak giving the military privacy, increased safety and an overall advantage in high-risk situations. Among civilians, some speeding drivers may use jamming devices to try to prevent detection by police and avoid fines.
Criminals use GPS jammers as cover for vehicle theft or to avoid toll charges or mileage charges. In the fleet world, GPS jamming could be used by a driver to prevent the employer from knowing where they are going with the company vehicle. GPS jamming is illegal in many countries, such as the U. In the U. A good way to visualize how it works is to stand with your arms straight out to either side, parallel with the floor, and then raise them up to create a degree angle from the floor.
If you were a GPS antenna on the roof of a datacenter, any RF signal coming from below your arms would be blocked. Since the most common source of jamming comes from people trying to evade fleet management tracking systems — in cars or trucks, or on the ground — the AJ antenna is a very effective method of protecting critical networks. It requires no special power, mounting, or placement considerations beyond what a standard antenna needs.
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