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Power grid, mobile or military radio - many systems today are highly dependent on GPS signals. Jammers can have dangerous consequences.

Recently at Newark Liberty International Airport: The newly installed GPS assistance system, intended to help pilots land the commercial plane in bad weather, fails twice a day, although the technology shows no errors. As the American trade magazine "New Scientist" reports, the airport administration found the error only after months: it was a truck driver who drove a GPS jammer on the highway because wanted to save the toll charged by GPS. The use of such devices for toll fraud clearly exceeds the horizon of legality, but their purchase is still very easy and cheap.

Mail-order sellers sell these devices for just over 20 euros, which the driver simply plugs into the vehicle's 12-volt cigarette lighter socket for operation. Electronics enthusiasts will find all the parts to build such a device in their dig box anyway. Global Positioning System (GPS) signals interfere so well because they arrive extremely weakly at the surface of the earth. The satellites each emit 100 watts at a distance of about 20,000 kilometers. It's like a loudspeaker announcement across town.

You can't hear it as soon as someone opens their mouth like an audio jamming transmitter right next to the receiving ear. As little as a watt or two of transmit power is enough for the little whines of the GPS to often cause confusion well beyond the intended range.

The sensitivity of GPS can be seen from the fact that it is large in strong solar winds and can black out an entire continent, or from the fact that a poorly shielded FM radio, tuned to the correct frequency, can receive GPS signals simultaneously from the actuated car blocked.

GPS plotters can interfere with receivers
In addition to the described toll fraud, there are other typical reasons for disturbing nearby GPS receivers. For example, there are a number of automatic vehicle tracker providers, some of which are used for fleet management, but primarily for tracking in the event of theft. The small battery boxes can be installed very concealed and send their current position to the provider's central tracking computer at set intervals via the mobile network.

Such a device has been standard in yachts for many years. It is also common for thieves to regularly disable this device. Police authorities also use small GPS trackers to monitor people, which they secretly attach to vehicles to be tracked. And finally, there are the control freaks who compulsively monitor their life partner electronically. One is inclined to see here the only legal reason for GPS jamming, although a relationship that escalates into electronic warfare is probably broken anyway.

Another trace is more common for not shouting but for falsifying the GPS signal. To do this, a scammer sends a slightly modified GPS timestamp on the original frequency with increased signal strength, because based on these timestamps the receiver normally triangulates its position relative to the satellites: after what time arrives what signal arrives with what timestamp of sending from what satellite? The receiver determines the distance to the satellites from when the signal travels. Their position is known, so the distances between them result in a clear position.

With some expertise, a GPS device can be misled by false timestamps. This may seem a bit complicated for cars, but could allow for potentially very profitable coups for Somali pirates or even hijackers. Because as a society, we're so used to the constant availability of GPS that we take it for granted. Alternative navigation capabilities are degrading more and more.

This can be seen in normal road traffic, as seemingly normal people drive their cars through the bushes, because "the navigation system said I should". This is also seen on the high seas among professionals. Anyone who has ever navigated a ship on a GPS chart plotter immediately wonders how they could navigate differently, and only a little later usually can't do it right.