FM Non-Duplication Rule

The FM Non-Duplication Rule was adopted by the U.S. Federal Communications Commission (FCC) on July 1, 1964, after a year's consideration. It limited holders of FM licenses in cities of more than 100,000 who also held AM licenses to simulcasting no more than 50 percent of their AM signal on the FM station. The commissioners considered the excessive simulcasting wasteful and an impediment to the development of FM broadcasting. A year later, the FCC reaffirmed the rule, and, after a delay requested by broadcasters, set its effective date for October 1965; some stations were granted exemptions if they could demonstrate their simulcasting served the public good.

Broadcasters generally resisted the rule at first, claiming it was overregulation that would impose considerable costs on stations for new personnel and equipment. It was challenged in court as a violation of the First Amendment and upheld in a decision written by future Supreme Court Chief Justice Warren Burger. Later the FCC extended the rule's requirements to 75 percent original content on FM stations and its applicability to stations in cities of more than 25,000.

The rule's implementation led to the rise of freeform radio in the late 1960s, where disc jockeys played whatever music they wanted without regard to genre or format, taking advantage of FM's higher sound quality and stereo capability. Most of their playlists tended toward rock of the era; in later years the canon of music and artists that developed evolved into the album-oriented^[1] and eventually classic rock formats.^[2] This growth often came at the expense of the classical music stations which had previously dominated the FM dial. By the late 1970s FM music stations had more listeners than their AM counterparts, even as they had largely moved away from their freeform roots, and in the 1980s the FCC repealed the rule to help AM stations, which had declined as FM grew.^[3]