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Encyclopedia > AM stereo

AM stereo is any of a number of mutually incompatible techniques for broadcasting two-channel audio in the mediumwave band in a manner that is compatible with receivers designed for standard amplitude modulation. There are two main classes of systems: independent sideband (ISB) systems, promoted principally by American broadcast engineer Leonard Kahn; and quadrature amplitude modulation (QAM) multiplexing systems (conceptually closer to FM stereo). Image File history File links Broom_icon. ... The term compatibility has the following meanings: In telecommunication, the capability of two or more items or components of equipment or material to exist or function in the same system or environment without mutual interference. ... Broadcasting is the distribution of audio and/or video signals which transmit programs to an audience. ... Stereophonic means having two channels of audio. ... An audio frequency (abbreviation: AF) is any frequency from about 20 hertz to about 20 kilohertz, which is the approximate range of sound frequencies that is audible to humans. ... Mediumwave radio transmissions serves as the most common band for broadcasting. ... In radio terminology, a receiver is an electronic circuit that receives a radio signal from an antenna and decodes the signal for use as sound, pictures, navigational-position information, etc. ... [[Amplitude modulation]] (AM) is a technique used in electronic communication, most commonly for transmitting information via a carrier wave wirelessly. ... Independent sideband (ISB) is an AM single sideband mode which is used with some AM radio transmissions. ... Broadcast engineering is the field of electrical engineering, and now to some extent radio and television broadcasting. ... QAM redirects here; for other uses of that abbreviation, see QAM (disambiguation). ... In telecommunications, multiplexing (also muxing or MUXing) is the combining of two or more information channels onto a common transmission medium using hardware called a multiplexer or (MUX). ... FM radio is a broadcast technology invented by Edwin Howard Armstrong that uses frequency modulation to provide high-fidelity broadcast radio sound. ...

Contents

History

Early experiments with stereo AM radio involved two separate stations broadcasting the left and right audio channels. This was not a very practical option, requiring a listener to have two radios tuned to one station. Synchronization was problematic, often resulting in a sort of ping-pong effect between the two channels. Reception was also likely to be different between the two stations—never mind that not many listeners had matched receivers of the same model or brand.


In the early 1980s five competing AM systems were available: The 1980s refers to the years of 1980 to 1989. ...

The Belar system, although available, was the least popular system, and may not have been used at all on any broadcast stations other than testing (perhaps on WJR). Harris Corporation NYSE: HRS is an international communications equipment company that produces wireless equipment, electronic systems, and both terrestrial and spaceborne antennas for use in the government, defense, and commercial sectors. ... ISB is an acronym for each of the following: Incredible String Band, a British musical group of the late 1960s. ... Magnavox (Latin for loud voice) is a consumer electronics company that is now part of Philips Consumer Electronics. ... The PMX or Pacific Media Expo started in 2003 in California by Mike Tatsugawa, former founder of Anime Expo. ... Motorola (NYSE: MOT) is an American multinational communications company based in Schaumburg, Illinois, a Chicago suburb. ... C-QUAM is the method of AM stereo broadcasting used in Canada, the United States and most other countries. ... WJR is a radio station in Detroit, Michigan, United States. ...


The Harris, Magnavox, and Motorola C-QAM (Compatible - Quadrature Amplitude Modulation) systems were fundamentally based on the same principle which phase modulates the primary carrier along with amplitude modulating it. The stereo information is placed on the phase modulated part of the carrier while the standard mono program was amplitude modulated as it normally would be in mono. Each of these systems would do it in slightly different ways. The Harris system utilized synchronous detection, and their initial system had a movable pilot signal, later changed to match the Motorola C-QAM pilot.


The Kahn-Hazeltine system worked on an entirely different principle which independently modulated the upper and lower sidebands separately to differentiate the difference in program material. If an AM station were broadcasting AM stereo using the Kahn system, stereophonic sound could be partially enjoyed by tuning two standard radios slightly to either side of the station, one to the right side of best tune and one to the left of best tune. The best way to experience the most stereo separation however was by using an AM Stereo tuner with appropriate circuitry for decoding the Kahn system.


The Harris, Magnavox, and Motorola C-QAM systems could only be decoded with an appropriate receiver. In the early '80s some electronics manufacturers, such as Sony, developed AM radios capable of receiving all four AM stereo systems. In the end, the two main systems that ended up battling it out to the death were the Kahn system and the Motorola C-QAM system. Eventually the C-QAM system became the FCC Standard for AM Stereo broadcasting. The Kahn system is still in use today, although not for stereophonic broadcasting. Experimentation by Leonard Kahn revealed that by using the Kahn system to put more high end on one sideband and more low end on the other sideband, you can improve the perceived coverage in the protected nulls of some directional AM signals. In some cases Kahn Powerside worked well, and in other cases it made no noticeable difference.


The C-QAM AM Stereo system is also still in use to this day, but on a shrinking number of stations. As many AM stations have switched their program formats from music to talk, the need for stereophonic sound has given way to the need for better signal to noise ratio, which is more easily attainable in mono.


The commercial radio industry is promoting a new Digital system marketed as HD Radio but also known generically as "In Band On Channel" IBOC. What IBOC does is insert a digital signal In Band On the next Channel above and below along with the analog audio. A Special HD Radio receiver will be needed to hear the digital audio. Recently, engineer Leonard Kahn has also devised a new analog/digital AM stereo system known as "CAM-D". HD Radio is an in-band on-channel (IBOC) digital radio system created by iBiquity for broadcasting via existing FM and AM radio stations. ... In-band on-channel (IBOC) is a method of transmitting digital and analog radio broadcast signals simultaneously on the same frequency. ... HD Radio is an in-band on-channel (IBOC) digital radio system created by iBiquity for broadcasting via existing FM and AM radio stations. ...


AMAX was a standard adopted by receiver manufacturers and broadcasters. There was a certain level of technical requirements for broadcast equipment manufacturers and AM Stereo receiver manufacturers to hold up to in order to attain AMAX certification. It was sort of a stamp of approval indicating that a consumer was buying a quality piece of AM Stereo receiving equipment. The AMAX program was developed to try and resurrect AM Stereo in the mid '90s once the FCC finally adopted C-QAM as the standard system for AM Stereo. Some auto manufacturers built quality AMAX AM stereo radios, and a Sony portable meeting AMAX AM stereo was available as well (the SRF-42). General Electric offers a mono AM radio, the GE SuperRadio III, which easily meets the bandwidth requirements of AMAX, but does not offer stereo AM audio. AMAX is an United States certification program developed by the Electronic Industries Association (EIA) and the National Association of Broadcasters (NAB) in 1993. ...


AM stereo timeline highlights

  • 1960 - AM Stereo first demonstrated on XTRA-AM, Tijuana, MX, using the Kahn ISB system.
  • 1963 - WHAZ runs a stereo program on eight AM stations, four on each channel.
  • c1980 - After at least five years of AM Stereo testing with five systems. Initially they select the Magnavox system as the official AM stereo standard. Their research is immediately accused of being flawed and incomplete.
  • 1982 - After another series of lawsuits and accusations, the FCC decides that the marketplace should decide and revokes the Magnavox certification as the AM stereo standard for political reasons. The marketplace continues fighting it out, and this becomes a death blow to the possibility of AM stereo becoming commonplace across the board.
  • 1985 - AM stereo officially begins in Australia, with the C-QAM standard. [1]
  • 1993 - FCC makes Motorola's C-QAM the AM stereo standard, and also requires extended band stations to broadcast in stereo. Canada also endorses the C-QAM system.

XTRA 570 AM. Southern California Sports Talk Radio Station External Link: http://www. ...

Current status

A famous European transmitter using AM stereo is Villebon sur Yvette on 864 kHz, which transmits France Bleu. This article is 150 kilobytes or more in size. ... France Bleu is the regional radio network of Radio France. ...


AM stereo is popular in Japan because of the limited number of FM stations in that country, and in Australia possibly because AM stations are more suited to covering large sparsely populated regions than FM stations, and the fact that unlike the American FCC, Australia was quick to pick a single standard (C-QAM). After some short lived experiments, the Independent Broadcasting Authority decided not to adopt AM stereo in Britain. Canada still has some quality AM stereo music stations on the air, and AM stereo receivers were more readily-available in Canada and Australia than the USA for some reason. The abbreviations FM, Fm, and fm may refer to: Electrical engineering Frequency modulation (FM) and its most common applications: FM broadcasting, used primarily to broadcast music and speech at VHF frequencies FM synthesis, a sound-generation technique popularized by early digital synthesizers Science Femtometre (fm), an SI measure of length... The Independent Broadcasting Authority (IBA) was the regulatory body in the United Kingdom for commercial television (ITV and Channel 4 - cable and satellite television were the responsibility of the Cable Authority) and radio broadcasts. ...


Some enthusiasts claim that AM stereo gives better stereo separation than FM stereo, but under skywave reception conditions, C-QAM stereo systems suffer from "platform motion" on first-generation AM stereo chipsets, but this was claimed to be corrected by the third-generation chipset. Label for 2. ... It has been suggested that this article or section be merged with Ionosphere. ...


External links


  Results from FactBites:
 
NationMaster - Encyclopedia: AM stereo (1915 words)
AM stereo is any of a number of mutually incompatible techniques for broadcasting two-channel audio in the mediumwave band in a manner that is compatible with receivers designed for standard amplitude modulation.
AM stereo is popular in Japan because of the limited number of FM stations in that country, and in Australia possibly because AM stations are more suited to covering large sparsely populated regions than FM stations, and the fact that unlike the American FCC, Australia was quick to pick a single standard (C-QAM).
There were five different AM Stereo systems being proposed to the FCC, and the FCC struggled with the decision of which one to choose as the single standard for AM Stereo broadcasting.
AM Stereo-Equipped Stereo Systems and Tuners (553 words)
TU-D99AMX - Tuner with Multi-System AM Stereo reception.
TU-S77AMX - Tuner with Multi-System AM Stereo reception.
TU-S772MX, TU-S777AMS - Tuners with Multi-System AM Stereo reception.
  More results at FactBites »

 
 

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