Draft:Radio communication
Use of radio waves for communication / From Wikipedia, the free encyclopedia
Radio communication or just radio is the use of radio waves for telecommunication.[1][2][3] Applications include radio broadcasting (audio) and television broadcasting, cell phones, two-way radios, wireless networking, and satellite communication, among numerous other uses.
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Radio waves are electromagnetic waves of frequency between 3 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connected to an antenna which radiates the waves. They are received by another antenna connected to a radio receiver. 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.
The existence of radio waves was first proven by German physicist Heinrich Hertz on 11 November 1886.[4] In the mid-1890s, building on techniques physicists were using to study electromagnetic waves, Guglielmo Marconi developed the first apparatus for long-distance radio communication,[5] sending a wireless Morse Code message to a recipient over a kilometer away in 1895,[6] and the first transatlantic signal on 12 December 1901.[7] The first commercial radio broadcast was transmitted on 2 November 1920, when the live returns of the Harding-Cox presidential election were broadcast by Westinghouse Electric and Manufacturing Company in Pittsburgh, under the call sign KDKA.[8]