FM broadcasting in the USA

FM broadcasting in the United States began in the 1930s at engineer and inventor Edwin Howard Armstrong's experimental station, W2XMN. The use of FM radio has been associated with higher sound quality in music radio.

In the United States FM radio stations broadcast at frequencies of 87.9–107.9 MHz. FM radio was developed in the United States by Edwin Armstrong.

During the 1930s, there were a small number of experimental (known as "Apex") stations attempting to broadcast high fidelity audio using wide-bandwidth AM on VHF frequencies. In 1937 W1XOJ was the first FM radio station, granted a construction permit by the Federal Communications Commission (FCC). On June 17, 1936, FM radio was demonstrated to the FCC for the first time. On January 5, 1940, Edwin H. Armstrong demonstrated FM broadcasting in a long-distance relay network, via five stations in five States. FM radio was assigned the 42 to 50 MHz band of the spectrum in 1940. There was interest in the new FM band by station owners. On March 1, 1941 W47NV began operations in Nashville, Tennessee, becoming the first modern commercial FM radio station. construction restrictions that went into place during World War II limited the growth of the new service.

Following the end of World War II, the FCC moved to standardize its frequency allocations. One area of concern was the effects of tropospheric and Sporadic E propagation, which at times reflected station signals over great distances, causing mutual interference. A particularly controversial proposal, spearheaded by RCA and chairman David Sarnoff, was that the FM band needed to be shifted to higher frequencies in order to avoid this potential problem, and to make "room" for more FM radio channels. This reassignment, whose covert goal by RCA was to disrupt the successful FM network that Edwin Armstrong had established on the old band was fiercely opposed as unneeded by Armstrong, but in the end RCA's point of view prevailed. The FCC made its decision final on June 27, 1945. It allocated one hundred FM channels from 88–108 MHz, and assigned the former FM band to 'non government fixed and mobile' (42–44 MHz), and television channel 1 (44–50 MHz). A period of allowing existing FM stations to broadcast on both low and high bands followed, though as late as 1947, in Detroit, there were only 3,000 FM receivers in use for the new band, and 21,000 for the old band. The dual band transition period ended at midnight on January 8, 1949, at which time any low band transmitters had to be shut down, officially making obsolete 395,000 receivers that had already been purchased by the public for the original band. Although converters allowing low band FM sets to receive high band were manufactured, they ultimately proved to be complicated to install, and often as (or more) expensive than buying a new high band set outright. The greater expense was to the radio stations themselves that had to rebuild their stations for the new FM radio band. FM radio as an industry did not recover significantly from the setback until the upsurge in high fidelity equipment in the late 1950s.

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