FM radio broadcasting relies on the frequency modulation transmission system developed in 1933 by Edwin Howard Armstrong and is a principal alternative to AM radio broadcasting. FM stations were originally developed in the late 1940s and the 1950s to counter the commercial format of AM stations, which depended heavily upon saturation advertising and repetitive play lists of popular songs. They catered to a more diversified audience and focused on in-dept news analysis and classical or semiclassical music.
With the proliferation of inexpensive AM-FM radios, the decline of network radio, and the increase in the number of local FM stations, however, the difference in programming between AM and FM stations since the 1960s have become less pronounced. Although some FM stations preserve the programming concept of early FM, many have altered format and adopted AM's more commercial approach.
Because FM radio is transmitted in a very high frequency range (88-108 MHz in