Montage Acoustics Speakers

Montage Acoustics reviews: 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.

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

Montage Acoustics BT4480: AM radio signals
AM radio signals can be severely disrupted in large urban centres by metal structures, tall buildings and sources of radio frequency interference (RFI) and electrical noise, such as electrical motors, fluorescent lights, or lightning. As a result, AM radio in many countries has lost its dominance as a music broadcasting service, and in many cities is now relegated to news, sports, religious and talk radio stations. Some musical genres – particularly country, oldies, nostalgia and ethnic music – survive on AM, especially in areas where FM frequencies are in short supply or in thinly populated or mountainous areas where FM coverage is poor.

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Distance covered by stereo FM transmission
The range of mono FM transmission is related to the transmitter's RF power, the antenna gain, and antenna height. The U.S. FCC publishes curves that aid in calculation of this maximum distance as a function of signal strength at the receiving location.

For stereo FM, the range is significantly reduced. This is due to the need to lower the modulation index of the main (sum) signal to accommodate the presence of the 38 kHz DSB-SC (double side-band suppressed-carrier) subcarrier and 19 kHz pilot tone. Many stations use extreme audio compression to keep the sound above the background noise for "distant" listeners, at the expense of degrading the sound quality. Montage Acoustics HD9001

Montage Acoustics reviews:Vacuum tubes
The discovery in 1912 of the amplifying ability of the Audion (triode) vacuum tube, invented in 1906 by Lee De Forest, solved these problems. The vacuum tube feedback oscillator invented in 1912 by Alexander Meissner and Edwin Armstrong, was a cheap source of continuous waves and could be easily modulated to make an AM transmitter. Nongovernmental radio transmission was prohibited in many countries during World War 1, but AM radio technology advanced greatly due to wartime research, and after the war the availability of cheap tubes sparked a great increase in the number of amateur radio stations experimenting with AM transmission of news or music, giving people more to listen to. New vacuum tube receivers coming on the market could power loudspeakers, so the entire family could sit and listen together, and people could dance to broadcast music. Vacuum tubes remained the central technology of radio for 50 years, until transistors replaced them in the 1960s, and they are still used in broadcast transmitters.