GPS jammers are transmitters
They come in many shapes and sizes, with varying capabilities. plugged into a standard cigarette lighter jack, a small jammer operating in the vehicle will disrupt GpS logging or GpS tracking systems for a radius of up to five yards. Mid-sized and larger jammers typically block a combination of GpS, cellphone, Wi-Fi, and other signals and thus also prevent the tracker from wirelessly reporting any location or status data.
In a test conducted by a federal law enforcement agency, GpS jamming devices were determined to be effective to approximately 65 feet. A large GpS jammer can disrupt any tracking device or receiver within a radius of several hundred yards.
GPS jammers send out a radio signal that’s the same frequency as the satellite signal. Since GpS satellite signals are weak, a GpS jamming device that puts out approximately 2 watts is sufficient to disrupt a GpS signal in a vehicle that’s approximately within 10 feet of the device. This leaves the in-vehicle system unable to establish its position and report back to a GpS tracking center, where the vehicle is registered.