Montage Acoustics reviews: 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.
Magnavox PMX system
In 1980 the FCC chose the Magnavox PMX system as the US standard. The FCC was savagely criticized by the other contenders, and lawsuits erupted. In 1982, the FCC reversed its decision and decided not to enforce a standard but allow multiple systems, to "let the marketplace decide". Meanwhile, other nations adopted AM stereo, many choosing Motorola's C-QUAM. Their choice of a single standard rather than allowing competing standards as the US, resulted in greater acceptance of AM stereo in these markets. In 1993, the FCC made C-QUAM system the US standard.
Globally, the adoption of stereo broadcasting was never great, and declined after 1990. With the continued migration of AM stations away from music to news, sports, and talk formats, receiver manufacturers saw little reason to adopt the more expensive stereo tuners, and thus radio stations have little incentive to upgrade to stereo transmission.Montage Acoustics BT4480
Montage Acoustics HD9001: Stereo FM in the late 1950s
In the late 1950s, several systems to add stereo to FM radio were considered by the FCC. Included were systems from 14 proponents including Crosley, Halstead, Electrical and Musical Industries, Ltd (EMI), Zenith, and General Electric. The individual systems were evaluated for their strengths and weaknesses during field tests in Uniontown, Pennsylvania using KDKA-FM in Pittsburgh as the originating station. The Crosley system was rejected by the FCC because it degraded the signal-to-noise ratio of the main channel and did not perform well under multipath conditions. In addition, it did not allow for SCA services because of its wide FM subcarrier bandwidth. The Halstead system was rejected due to lack of high frequency stereo separation and reduction in the main channel signal-to-noise ratio. The GE and Zenith systems, so similar that they were considered theoretically identical, were formally approved by the FCC in April 1961 as the standard stereo FM broadcasting method in the United States and later adopted by most other countries.
Montage Acoustics
FM broadcast station frequency
The frequency of an FM broadcast station (more strictly its assigned nominal centre frequency) is usually an exact multiple of 100 kHz. In most of South Korea, the Americas and the Caribbean, only odd multiples are used. In some parts of Europe, Greenland and Africa, only even multiples are used. In Italy, multiples of 50 kHz are used. There are other unusual and obsolete standards in some countries, including 0.001, 0.01, 0.03, 0.074, 0.5, and 0.3 MHz. However, to minimise cross-channel interference, stations operating from the same or geographically close transmitters tend to keep to at least a 0.5 MHz frequency separation even when closer spacing is technically permitted, with closer tunings reserved for more distantly spaced transmitters as potentially interfering signals are already more attenuated and so have less effect on neighbouring frequencies. Montage Acoustics BT4480
Montage Acoustics:Home radio 1920's
In the 1920s the home radio evolved from a forbidding technological device which was esthetically unattractive and difficult to operate, to a consumer item, a piece of furniture, housed in an attractive wooden cabinet, with simple controls designed for anyone to operate, which occupied a place of honor in the living room. Prior to the introduction of the high-fidelity, long-playing record in the late 1940s, AM radio offered the highest sound quality available in a home audio device. Luxury models offered large speakers, "electric eye" tuning (a special type of vacuum tube, which provided a visual aid in tuning), mechanical push-button "memory" of favorite stations, sometimes with booklets of adhesive labels for the buttons with station call letters, and -- an inexpensive but impressive feature -- shortwave bands that allowed access to distant, often foreign, stations. Accessory, then factory-installed radios became available for cars.
