Edwin Armstrong began testing his new 43-48 megacycle frequency modulation system, much of which was patented in 1933. During the summer of 1934, tests were conducted between the Empire State building and Westhampton Beach, Long Island which proved excellent. The first known Chicago area FM broadcast station was W9XZR on 42.8 megacycles, owned by the Zenith Radio Corporation which began broadcasting in 1939. In 1942 the call was changed to W51C transmitting on 45.1 megacycles. The transmitter and studio was on the 45th Floor of the Field Building (later the La Salle Nat’l Bank Building) at 135 S. La Salle Street. Metromedia Radio purchased WDHF on March 15, 1973 and changed to a live adult contemporary format. WDHF changed to Top 40 on June 20, 1974 and began running Casey Casem’s American Top 40. On December 1, 1976, WDHF changed call letters to WMET and continued with AT 40 until the station switched to an album rock format in early 1979 as WLS ran the syndication into the early 1980’s… read more >
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