Radio jamming

A radio jammer is any device that deliberately blocks, jams or interferes with authorized wireless communications. According to the Federal Communications Commission, jammers are illegal and their use can result in large fines.

In some cases jammers work by the transmission of radio signals that disrupt communications by decreasing the signal-to-noise ratio.

The concept can be used in wireless data networks to disrupt information flow. It is a common form of censorship in totalitarian countries, in order to prevent foreign radio stations in border areas from reaching the country. As an example, the Islamic regime in Iran has been using radio jamming to block free information across large cities and the capital, Tehran.

Jamming is usually distinguished from interference that can occur due to device malfunctions or other accidental circumstances. Devices that simply cause interference are regulated under different regulations. Unintentional 'jamming' occurs when an operator transmits on a busy frequency without first checking whether it is in use, or without being able to hear stations using the frequency. Another form of unintentional jamming occurs when equipment accidentally radiates a signal, such as a cable television plant that accidentally emits on an aircraft emergency frequency.