The first practical radio transmitters and receivers were developed around 1895–1896 by Italian Guglielmo Marconi, and radio began to be used commercially around 1900. Radio waves were first identified and studied by German physicist Heinrich Hertz in 1886. The noun radio is also used to mean a broadcast radio receiver. In wireless radio remote control devices like drones, garage door openers, and keyless entry systems, radio signals transmitted from a controller device control the actions of a remote device.Īpplications of radio waves that do not involve transmitting the waves significant distances, such as RF heating used in industrial processes and microwave ovens, and medical uses such as diathermy and MRI machines, are not usually called radio. In radio navigation systems such as GPS and VOR, a mobile receiver accepts radio signals from navigational radio beacons whose position is known, and by precisely measuring the arrival time of the radio waves the receiver can calculate its position on Earth. In radar, used to locate and track objects like aircraft, ships, spacecraft and missiles, a beam of radio waves emitted by a radar transmitter reflects off the target object, and the reflected waves reveal the object's location. In radio communication, used in radio and television broadcasting, cell phones, two-way radios, wireless networking, and satellite communication, among numerous other uses, radio waves are used to carry information across space from a transmitter to a receiver, by modulating the radio signal (impressing an information signal on the radio wave by varying some aspect of the wave) in the transmitter. Radio is very widely used in modern technology, in radio communication, radar, radio navigation, remote control, remote sensing, and other applications. 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 waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). Radio is the technology of signaling and communicating using radio waves. Antennas of both kinds are shown here, along with round dishes and drums for point-to-point microwave communications (for example from studio to transmitter).
FM and television transmitting antennas are often located on high towers or mountain peaks, to maximize transmission range. A variety of radio antennas on Sandia Peak near Albuquerque, New Mexico, US.
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