Contact your audience through FM and AM radio. Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connected to an antenna which radiates the waves, and received by another antenna connected to a radio receiver. Radio is very widely used in modern technology, in radio communication, radar, radio navigation, remote control, remote sensing and other applications. According to Nielsen's measurements, far more than 200 million Americans aged 18 and older listen to the radio at least once a week, equaling a reach of 91 percent of the adult population.