Radio in the United States

Radio broadcasting in the United States is a major mass medium. Unlike radio in most other countries, American radio has historically relied primarily on commercial advertising sponsorship on for-profit stations. There is a smaller not-for-profit "public" sector, funded chiefly by listeners. Shortwave broadcasting in the United States includes federal government programs for overseas audiences. Radio broadcasting became popular in the 1920s, alongside the new film industry. The arrival of television in the 1950s forced radio into a niche role, as leading participants moved into the much larger field of television. In the 21st century, radio has been adjusting to the arrival of the Internet and Internet radio.

In 1912, most amateur-radio transmissions were restricted to wavelengths below 200 meters (i.e., frequencies above 1500 kHz) to prevent interference to future commercial broadcasters. The beginning of regular, commercially licensed radio broadcasting in the United States in 1920, along with the concurrent development of sound and color film in that decade, ended the print monopoly of mass media and opened the doors to the immediate (and pervasive) electronic media. By 1928, the United States had three national radio networks: two owned by NBC (the National Broadcasting Company), and one by CBS (the Columbia Broadcasting System). Until 1943, there were four major national radio networks: two owned by NBC, one owned by CBS and one owned by Mutual Broadcasting System. Stations were connected by broadcast-quality, leased telephone lines. NBC's second network became ABC, the American Broadcasting Company.

By 1919, after the war, radio pioneers across the country resumed transmissions. The early stations gained new call signs. Many early stations were started by newspapers worried radio might replace their newspapers. 8XK became KDKA in 1920. KDKA received the first federal license and began broadcasting on November 2, 1920. Its signal covered much of the country, and its very existence encouraged young men to build crystal sets (with ear phones) to listen to the new technical marvel. Entrepreneurs set up stations primarily with the goal of selling expensive console radio sets that the whole family could listen to, or which restaurants and shops would buy to attract customers.

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