How Cell Phone Jammers Work

A cell phone jammer is a device that creates a temporary dead zone where all cell phone traffic in the immediate vicinity is either limited or disrupted. These devices are usually used by the police or the military to control communication in hostage situations, during a bomb threat or in a military situation. There are also portable cell phone jammers that allow owners to disable cell phone usage in their immediate vicinity, usually within a few meters radius. When a cell phone jammer is activated, mobile users will usually think that they have hit a dead spot in the cell phone coverage. Some jammers are designed to cover office buildings, churches and movie theaters. In the United States it is illegal to use a cell phone jammer. So how do these devices work?

A cell phone works by transmitting and receiving radio signals from cell towers. Cell towers divide areas into cells and each cell is served by a cell tower or several towers. A jamming device works by transmitting a radio signal on the same frequency as the cell phone. This results in the cell phone signal canceling out with the cell phone jammer signal. As a result, communication ceases. Cell phones are however designed to add power in case there is low level interference. So how do jammers handle this? They also recognize this change and match the power to that of the phone, effectively causing signal cancellation.

Cell phones are full duplex devices. This means that they use two frequencies to communicate, one of listening and the other for talking, simultaneously. Some jammers will work by just blocking one of the frequencies. This in turn will trick the phone into thinking that there is no service and will therefore effectively result in a denial of service for the cell phone user. An effective cell phone jammer needs to broadcast on the correct frequencies in order for it to work.

A cell phone jammer is a very basic device electronically. It consists of an antenna within an electronic cabinet, the circuitry and the power supply. The circuitry of the cell phone jammer consists of an oscillator that generates the radio signal, a tuning circuit that controls the voltage to the oscillator, a noise generator that outputs the specified frequency and a radio frequency amplification section that boosts the radio frequency output to jam a signal. To the ultra paranoid, a cell phone jammer is the ultimate weapon for some peace and quiet from blabber mouth phone users.