Montage Acoustics
Montage Acoustics Speakers: Shortwave broadcasting
The discovery in the 1920s of the "skip" or "skywave" propagation mechanism, in which high frequency radio waves are reflected back to Earth beyond the horizon by the ionosphere, made the shortwave frequencies above 1 MHz, previously considered useless, a useful band for long distance broadcasting.
Competing media
In the 1940s two new broadcast media evolved in the US which competed with AM: FM radio and television. By the 1950s, the dominance of AM radio over home entertainment was ended. Television replaced AM radio as an evening family pastime; instead of sitting and listening to the radio, families would watch television. By the 1970s FM radio, due to its superior audio quality, attracted serious audiophiles.Montage Acoustics HD9001
Montage Acoustics BT4480: United States
In the US, the nationwide telephone carrier AT&T was the first to create a network and take the radical step of commercial advertising. It developed a broadcasting model based on its telephony business: "toll" broadcasting. Its flagship station, WEAF in New York, in August 1922 was first to air commercial advertising, selling half-hour and hour blocks of airtime to commercial "sponsors" that developed entertainment shows containing commercial messages. It had a monopoly on quality telephone lines, and by 1924 had linked 12 stations in Eastern cities into a "chain". RCA and Westinghouse attempted to organize their own network around their flagship WJZ, but were hampered by AT&T's refusal to lease them lines. In 1925 court decisions stripped AT&T of its monopoly over broadcasting, and it decided to get out of radio. AT&T sold WEAF to RCA, which formed the nucleus of the new NBC network. In 1927, to reduce the "chaos" on the airwaves, the government came down on the side of the advertising model, establishing two classes of broadcast licenses: the "A" or "general public interest" stations which sold time impartially to anyone, received favorable frequency assignments and flourished, and the "B" or nonprofit "propaganda" stations, mainly special-interest, political or religious stations which represented a point of view, were phased out.
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The AM radio industry
The AM radio industry suffered a serious loss of audience and advertising revenue during this time, and the value of an AM broadcast license was eventually to decline substantially. The industry coped with this by developing new "narrowcasting" strategies. Network broadcasting gave way to format broadcasting; instead of broadcasting the same programs all over the country, AM stations specialized in different "formats" which appealed to different audience segments: regional and local news, sports, "talk" programs, programs targeted at minorities. "Talk radio", which avoided the need for the broadcaster to pay music royalties, appeared during this period as a consequence of the less expensive "air time", and the need to develop alternative programming, at reasonable cost, to replace the lost network programming. Rather than live music, stations played cheaper recorded music, and developed the "Top 40" format, which capitalized on (and created) the popularity of new rhythm and blues and rock music. Montage Acoustics reviews
Montage Acoustics:Shortcomings of AM broadcasting
AM radio was often noisy. There was no protection from static created by lightning, electrical equipment, and other sources of signal pollution. Especially at night, conflict between nearby and distant stations using a single frequency was common, and required many smaller stations to operate at much reduced power after sundown. Finally, the 10 kilohertz minimum separation between stations in the United States limited fidelity to sounds much lower than the upper limit of human hearing, and the advent of high-fidelity recording equipment created a demand for high-fidelity radio.
As a result of these shortcomings, especially the noise issue, RCA in 1934 hired Edwin Howard Armstrong to test his FM broadcasting system, which started to be deployed in the 1940s, but because of a channel allocation change in 1946 would not achieve dominance over AM until the end of the 1970s.
