I
infrared radiation , and consisting of the range of frequencies used for navigation signals, AM and FM broadcasting, television transmissions, cell-phone communications, and various forms of radar .
For radio transmission, information is imparted to a carrier wave by varying (modulating) its amplitude, frequency, or duration. The technology of radio arose from the work of Michael Faraday , James Clerk Maxwell , Heinrich Hertz , Guglielmo Marconi , and others, and improvement followed the development of the vacuum tube , the electronic-tube oscillator , the tuned circuit , and other components. Later innovations have included the replacement of tubes by transistors and of wires by printed circuits . See also radio and radar astronomy .
II
[c mediumvioletred] (as used in expressions)
pulsating radio star
quasi stellar radio source
National Public Radio
radio and radar astronomy
radio telescope
radio wave
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