Radio

Radio:-

                In 1864, James Clerk Maxwell formulated the electromagnetic theory of light and predicted the existence of radio waves; the underlying set of equations bears his name. The existence of radio waves was confirmed experimentally by Heinrich Hertz in 1887. In 1894, Oliver Lodge demonstrated wireless communication over a relatively short distance (150 yards). Then, on December 12, 1901, Guglielmo Marconi received a radio signal at Signal Hill in Newfoundland; the radio signal had originated in Cornwall, England, 1700 miles away across the Atlantic. The way was thereby opened toward a tremendous broadening of the scope of communications. In 1906, Reginald Fessenden, a self-educated academic, made history by conducting the first radio broadcast. In 1918, Edwin H. Armstrong invented the superheterodyne radio receiver; to this day, almost all radio receivers are of this type. In 1933, Armstrong demonstrated another revolutionary concept—namely, a modulation scheme that he called frequency modulation (FM). Armstrong’s paper making the case for FM radio was published in 1936.