AM broadcasting is radio broadcasting using amplitude modulation (AM) transmissions. It was the first method developed for making audio radio transmissions, and is still used worldwide, primarily for medium wave (also known as "AM band") transmissions, but also on the longwave and shortwave radio bands.
109-431: WVAL (800 AM ) is a radio station serving St. Cloud, Minnesota airing a classic country format. It airs news on the hour from CBS News Radio . The station is owned by Tri-County Broadcasting . WVAL first aired in 1963, went on hiatus in the early 1980s, returning to the airwaves in 1999. The station shares AM towers with its three other sister stations, WMIN, WBHR, and WXYG. There are seven total towers. The call sign
218-472: A "chain". The Radio Corporation of America (RCA), General Electric , and Westinghouse organized a competing network around its own flagship station, RCA's WJZ (now WABC) in New York City, but were hampered by AT&T's refusal to lease connecting lines or allow them to sell airtime. In 1926 AT&T sold its radio operations to RCA, which used them to form the nucleus of the new NBC network. By
327-846: A 10 shilling receiver license fee. Both highbrow and mass-appeal programmes were carried by the National and Regional networks. The period from the early 1920s through the 1940s is often called the "Golden Age of Radio". During this period AM radio was the main source of home entertainment, until it was replaced by television. For the first time entertainment was provided from outside the home, replacing traditional forms of entertainment such as oral storytelling and music from family members. New forms were created, including radio plays , mystery serials, soap operas , quiz shows , variety hours , situation comedies and children's shows . Radio news, including remote reporting, allowed listeners to be vicariously present at notable events. Radio greatly eased
436-875: A Public Notice in the Murray Ledger stating that the Wireless Telephone Company of America had "gone out of existence", and "My inventions have reverted back to me." He also noted that he was continuing his wireless telephone research, using the "over two thousand dollars" he had received from that company's promoter. Stubblefield returned once again to investigating using induction, rather than conduction, for his wireless telephone system. This approach employed large circular induction coils, that no longer needed ground connections. He carefully documented his progress, preparing affidavits that in 1903 he had transmitted 375 feet (114 m), and in 1904 reached 600 feet (180 m). The total wire required for
545-511: A U.S. patent for a wireless telephone system that used magnetic induction . However, he was ultimately unsuccessful in commercializing his inventions. He later went into seclusion, and died alone in 1928. Disagreement exists whether Stubblefield's communications technology can be classified as radio , and if his 1902 demonstrations could be considered the first "radio broadcasts". Most reviews of his efforts have concluded that they were not radio transmissions, because his devices, although they used
654-570: A central station to all parts of the United States", he was unable to overcome the inherent distance limitations of this technology. The earliest public radiotelegraph broadcasts were provided as government services, beginning with daily time signals inaugurated on January 1, 1905, by a number of U.S. Navy stations. In Europe, signals transmitted from a station located on the Eiffel Tower were received throughout much of Europe. In both
763-610: A concerted attempt to specify performance of AM receivers through the 1993 AMAX standard, a joint effort of the EIA and the NAB, with FCC backing... The FCC rapidly followed up on this with codification of the CQUAM AM stereo standard, also in 1993. At this point, the stage appeared to be set for rejuvenation of the AM band. Nevertheless, with the legacy of confusion and disappointment in the rollout of
872-635: A consortium, the British Broadcasting Company (BBC), established on 18 October 1922, which was given a monopoly on broadcasting. This enterprise was supported by a tax on radio sets sales, plus an annual license fee on receivers, collected by the Post Office. Initially the eight stations were allowed regional autonomy. In 1927, the original broadcasting organization was replaced by a government chartered British Broadcasting Corporation . an independent nonprofit supported solely by
981-564: A continuous-wave (CW) transmitter. Fessenden began his research on audio transmissions while doing developmental work for the United States Weather Service on Cobb Island, Maryland. Because he did not yet have a continuous-wave transmitter, initially he worked with an experimental "high-frequency spark" transmitter, taking advantage of the fact that the higher the spark rate, the closer a spark-gap transmission comes to producing continuous waves. He later reported that, in
1090-489: A decade of research and testing, he felt that his wireless telephone had now been perfected to the point that it was ready for commercialization, and began a series of demonstrations to publicize his work and attract investment. On Christmas Eve, December 24, 1901, he successfully transmitted ¼ mile (400 meters) to his home, where "A party of children were gathered there and at the receiver obtained messages from Santa Claus", and had local residents sign affidavits attesting to
1199-580: A few " telephone newspaper " systems, most of which were established in Europe, beginning with the Paris Théâtrophone . With this in mind, most early radiotelephone development envisioned that the device would be more profitably developed as a "wireless telephone" for personal communication, or for providing links where regular telephone lines could not be run, rather than for the uncertain finances of broadcasting. The person generally credited as
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#17328014414421308-463: A few hundred ( Hz ), to increase its rotational speed and so generate currents of tens-of-thousands Hz, thus producing a steady continuous-wave transmission when connected to an aerial. The next step, adopted from standard wire-telephone practice, was to insert a simple carbon microphone into the transmission line, to modulate the carrier wave signal to produce AM audio transmissions. However, it would take many years of expensive development before even
1417-401: A form of "wireless", employed conduction and inductive fields, while the standard definition of radio is the transmission of electromagnetic radiation . However, Stubblefield may have been the first to simultaneously transmit audio wirelessly to multiple receivers, albeit over relatively short distances, while predicting the eventual development of broadcasting on a national scale. Stubblefield
1526-516: A home audio device prior to the introduction of the high-fidelity , long-playing record in the late 1940s. Listening habits changed in the 1960s due to the introduction of the revolutionary transistor radio (Regency TR-1, the first transistor radio released December 1954), which was made possible by the invention of the transistor in 1948. (The transistor was invented at Bell labs and released in June 1948.) Their compact size — small enough to fit in
1635-474: A listening site at Plymouth, Massachusetts. An American Telephone Journal account of the December 21 alternator-transmitter demonstration included the statement that "It is admirably adapted to the transmission of news, music, etc. as, owing to the fact that no wires are needed, simultaneous transmission to many subscribers can be effected as easily as to a few", echoing the words of a handout distributed to
1744-487: A majority of early broadcasting stations operated on mediumwave frequencies, whose limited range generally restricted them to local audiences. One method for overcoming this limitation, as well as a method for sharing program costs, was to create radio networks , linking stations together with telephone lines to provide a nationwide audience. In the U.S., the American Telephone and Telegraph Company (AT&T)
1853-506: A national scale. The introduction of nationwide talk shows, most prominently Rush Limbaugh 's beginning in 1988, was sometimes credited with "saving" AM radio. However, these stations tended to attract older listeners who were of lesser interest to advertisers, and AM radio's audience share continued to erode. In 1961, the FCC adopted a single standard for FM stereo transmissions, which was widely credited with enhancing FM's popularity. Developing
1962-399: A policy allowing AM stations to simulcast over FM translator stations. Translators had previously been available only to FM broadcasters, in order to increase coverage in fringe areas. Their assignment for use by AM stations was intended to approximate the station's daytime coverage, which in cases where the stations reduced power at night, often resulted in expanded nighttime coverage. Although
2071-534: A power source and ground terminal for wireless telephony. After the winding-down of his acoustic telephone business, Stubblefield reviewed possible alternatives that would avoid infringing on the Bell telephone patents, and began researching wireless options. Because he never filed for a patent for his early work, the technical details of his experiments are largely unknown. But, based on contemporary descriptions, it appears that they initially employed induction, similar to
2180-562: A promoter, Gerald Fennel, traveled to Murray from New York City to enlist Stubblefield in a commercial venture. While negotiating, Stubblefield next embarked on his most publicized promotional trip. On March 20, 1902, he demonstrated his system in Washington, D.C., where voice and music transmissions were made over a third of a mile (535 meters) from the steamer Bartholdi , anchored in the Potomac River, to shore. This particular test
2289-486: A prototype alternator-transmitter would be ready, and a few years beyond that for high-power versions to become available. Fessenden worked with General Electric 's (GE) Ernst F. W. Alexanderson , who in August 1906 delivered an improved model which operated at a transmitting frequency of approximately 50 kHz, although at low power. The alternator-transmitter achieved the goal of transmitting quality audio signals, but
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#17328014414422398-423: A result, AM radio tends to do best in areas where FM frequencies are in short supply, or in thinly populated or mountainous areas where FM coverage is poor. Great care must be taken to avoid mutual interference between stations operating on the same frequency. In general, an AM transmission needs to be about 20 times stronger than an interfering signal to avoid a reduction in quality, in contrast to FM signals, where
2507-449: A series of inventions. His first patent, U.S. patent 329,864 , was issued on November 3, 1885, for a tool for lighting coal oil lamps without having to remove the glass chimney. In late 1886, Stubblefield began to sell and install acoustic telephones—an early and somewhat limited form of the telephone, which, instead of using electricity, employed a taut wire to carry sound vibrations directly between two soundboxes which were located at
2616-452: A shirt pocket — and lower power requirements, compared to vacuum tubes, meant that for the first time radio receivers were readily portable. The transistor radio became the most widely used communication device in history, with billions manufactured by the 1970s. Radio became a ubiquitous "companion medium" which people could take with them anywhere they went. The demarcation between what is considered "experimental" and "organized" broadcasting
2725-427: A short-range "wireless telephone" demonstration, that included simultaneously broadcasting speech and music to seven locations throughout Murray, Kentucky. However, this was transmitted using induction rather than radio signals, and although Stubblefield predicted that his system would be perfected so that "it will be possible to communicate with hundreds of homes at the same time", and "a single message can be sent from
2834-440: A television and recording personality under the professional name Troy Cory. Initially Stubblefield supported his family by farming. (His farm land later became part of the campus of Murray State University .) From 1907 to 1911, he operated a home school called "The Nathan Stubblefield Industrial School," or "Teléph-on-délgreen Industrial School". Despite very limited finances, in his spare time Stubblefield worked on developing
2943-461: A widespread audience — dates back to the founding period of radio development, even though the earliest radio transmissions, originally known as "Hertzian radiation" and "wireless telegraphy", used spark-gap transmitters that could only transmit the dots-and-dashes of Morse code . In October 1898 a London publication, The Electrician , noted that "there are rare cases where, as Dr. [Oliver] Lodge once expressed it, it might be advantageous to 'shout'
3052-611: A wireless telephone developed by Amos Dolbear, which was issued U.S. patent 350,299 in 1886. Information for this period is very limited, but in 1935 a former neighbor, Rainey T. Wells, reported that in 1892 Stubblefield gave him a telephone receiver, and had Wells walk a short distance away from Stubblefield's shack, after which he was amazed to distinctly hear the words "Hello, Rainey", followed by additional speech from Stubblefield. Because later references refer to earth connections, it appears that Stubblefield subsequently switched to using ground currents instead of induction. Following
3161-488: Is a device that transmits and receives voice over considerable distance without connecting wires. Stubblefield invented, manufactured, and demonstrated such a device and did so before anyone else on the planet." However, there had actually been earlier audio wireless transmissions, including, beginning in 1880, the photophone , invented by Alexander Graham Bell and Charles Sumner Tainter , which employed light beams, and Amos Dolbear 's "electrostatic telephone", for which it
3270-472: Is based on owner Herb Hoppe's wife Val. In January 1996, Tri-County Broadcasting filed to build a radio station on 800 kHz in Sauk Rapids, which came to air on March 29, 1999. However, the frequency was not new to the company. The original WVAL had operated on the frequency until moving to 660 kHz in 1983; however, relaxed ownership rules allowed the company to start a second AM. Tri-County moved
3379-406: Is comparable to or better in audio quality than a standard analog broadcast". Despite the various actions, AM band audiences continued to contract, and the number of stations began to slowly decline. A 2009 FCC review reported that "The story of AM radio over the last 50 years has been a transition from being the dominant form of audio entertainment for all age groups to being almost non-existent to
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3488-502: Is largely arbitrary. Listed below are some of the early AM radio broadcasts, which, due to their irregular schedules and limited purposes, can be classified as "experimental": People who weren't around in the Twenties when radio exploded can't know what it meant, this milestone for mankind. Suddenly, with radio, there was instant human communication. No longer were our homes isolated and lonely and silent. The world came into our homes for
3597-645: Is simpler than later transmission systems. An AM receiver detects amplitude variations in the radio waves at a particular frequency, then amplifies changes in the signal voltage to operate a loudspeaker or earphone . However, the simplicity of AM transmission also makes it vulnerable to "static" ( radio noise , radio frequency interference ) created by both natural atmospheric electrical activity such as lightning, and electrical and electronic equipment, including fluorescent lights, motors and vehicle ignition systems. In large urban centers, AM radio signals can be severely disrupted by metal structures and tall buildings. As
3706-578: The Electronic Industries Association (EIA) and the National Association of Broadcasters (NAB) with the intention of helping AM stations, especially ones with musical formats, become more competitive with FM broadcasters by promoting better quality receivers. However, the stereo AM and AMAX initiatives had little impact, and a 2015 review of these events concluded that Initially the consumer manufacturers made
3815-625: The Emergency Alert System (EAS). Some automakers have been eliminating AM radio from their electric vehicles (EVs) due to interference from the electric motors , but the lawmakers argue that this is a safety risk and that car owners should have access to AM radio regardless of the type of vehicle they drive. The proposed legislation would require all new vehicles to include AM radio at no additional charge, and it would also require automakers that have already eliminated AM radio to inform customers of alternatives. AM radio technology
3924-493: The Federal Emergency Management Agency (FEMA) expressed concerns that this would reduce the effectiveness of emergency communications. In May 2023, a bipartisan group of lawmakers in the United States introduced legislation making it illegal for automakers to eliminate AM radio from their cars. The lawmakers argue that AM radio is an important tool for public safety due to being a component of
4033-431: The electrolytic detector and thermionic diode ( Fleming valve ) were invented by Reginald Fessenden and John Ambrose Fleming , respectively. Most important, in 1904–1906 the crystal detector , the simplest and cheapest AM detector, was developed by G. W. Pickard . Homemade crystal radios spread rapidly during the next 15 years, providing ready audiences for the first radio broadcasts. One limitation of crystals sets
4142-430: The " capture effect " means that the dominant signal needs to only be about twice as strong as the interfering one. To allow room for more stations on the mediumwave broadcast band in the United States, in June 1989 the FCC adopted a National Radio Systems Committee (NRSC) standard that limited maximum transmitted audio bandwidth to 10.2 kHz, limiting occupied bandwidth to 20.4 kHz. The former audio limitation
4251-603: The 1930s, most of the major radio stations in the country were affiliated with networks owned by two companies, NBC and CBS . In 1934, a third national network, the Mutual Radio Network , was formed as a cooperative owned by its stations. A second country which quickly adopted network programming was the United Kingdom, and its national network quickly became a prototype for a state-managed monopoly of broadcasting. A rising interest in radio broadcasting by
4360-660: The 1940s two new broadcast media, FM radio and television , began to provide extensive competition with the established broadcasting services. The AM radio industry suffered a serious loss of audience and advertising revenue, and coped by developing new strategies. Network broadcasting gave way to format broadcasting: instead of broadcasting the same programs all over the country, stations individually adopted specialized formats which appealed to different audiences, such as regional and local news, sports, "talk" programs, and programs targeted at minorities. Instead of live music, most stations began playing less expensive recorded music. In
4469-532: The AM radio industry in the United States developed technology for broadcasting in stereo . Other nations adopted AM stereo, most commonly choosing Motorola's C-QUAM, and in 1993 the United States also made the C-QUAM system its standard, after a period allowing four different standards to compete. The selection of a single standard improved acceptance of AM stereo , however overall there was limited adoption of AM stereo worldwide, and interest declined after 1990. With
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4578-517: The Birthplace of Radio, and Stubblefield as the Father of Broadcasting. Loren J. Hortin, Journalism Professor at Murray State, organized his students to investigate Stubblefield's work, leading to the dedication of a monument on the campus in 1930. Hortin, adopting an expanded definition of "radio" to include wireless transmissions that did not employ electromagnetic radiation, later contended: "Radio
4687-531: The British public pressured the government to reintroduce the service, following its suspension in 1920. However, the government also wanted to avoid what it termed the "chaotic" U.S. experience of allowing large numbers of stations to operate with few restrictions. There were also concerns about broadcasting becoming dominated by the Marconi company. Arrangements were made for six large radio manufacturers to form
4796-487: The Territory of Arizona, the Wireless Telephone Company of America. The firm had a $ 5,000,000 capitalization, with shares set at a par value of $ 1 each. Gerald Fennel offered Stubblefield 500,000 shares of stock in exchange for the rights to his wireless telephone technology. A June 1902 stock-promotion advertisement for the company, echoing the excessive claims of contemporary wireless telegraph companies, proclaimed: "With
4905-411: The Twenties when radio exploded can't know what it meant, this milestone for mankind. Suddenly, with radio, there was instant human communication. No longer were our homes isolated and lonely and silent. The world came into our homes for the first time. Music came pouring in. Laughter came in. News came in. The world shrank, with radio. The idea of broadcasting — the unrestricted transmission of signals to
5014-599: The U.S., for example) subject to international agreements. Nathan Stubblefield Nathan Beverly Stubblefield (November 22, 1860 – March 28, 1928) was an American inventor best known for his wireless telephone work. Self-described as a "practical farmer, fruit grower and electrician", he received widespread attention in early 1902 when he gave a series of public demonstrations of a battery-operated wireless telephone, which could be transported to different locations and used on mobile platforms such as boats. While this initial design employed conduction , in 1908 he received
5123-457: The Union". Stubblefield returned to Murray, where he faced considerable skepticism—a March 1903 review of his "earth battery" and wireless telephony endeavors stated: "...the people in this section of the country are yet wondering whether he is simply a crank or will yet emerge some day from his obscurity to astonish the whole civilized world with a great discovery". Later that same year, he posted
5232-694: The United States and France this led to a small market of receiver lines geared for jewelers who needed accurate time to set their clocks, including the Ondophone in France, and the De Forest RS-100 Jewelers Time Receiver in the United States The ability to pick up time signal broadcasts, in addition to Morse code weather reports and news summaries, also attracted the interest of amateur radio enthusiasts. It
5341-644: The United States. With travel expenses financed by Fennel, Stubblefield made additional successful demonstrations in Philadelphia from May 30 to June 7, 1902, spanning a distance of around a mile (1600 meters). Tests followed in New York City beginning on June 11, 1902, which were less successful, with the explanation for the difficulties encountered including the rocky soil in Battery Park, and electrical interference from local alternating current power distribution. Stubblefield quickly became distrustful of
5450-490: The WVAL call sign from 660 kHz to the new station and also revived the music it had played in its glory days in the 1970s and early 1980s with classic country , a rarity for the time. 45°36′18″N 94°08′21″W / 45.60500°N 94.13917°W / 45.60500; -94.13917 AM broadcasting The earliest experimental AM transmissions began in the early 1900s. However, widespread AM broadcasting
5559-421: The acoustic sales by 1890. In 1898, Stubblefield was issued U.S. patent 600,457 for an "electric battery", which was an electrolytic coil of iron and insulated copper wire that was immersed in liquid or buried in the ground. Stubblefield made the unsubstantiated claim that, combined with normal battery operation, his device also drew additional power from the earth. However, it did successfully serve as both
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#17328014414425668-568: The age of 14, with his father's death, which left Stubblefield an orphan in the care of his step-mother. However, he continued to develop his technical knowledge by reading contemporary scientific publications, such as Scientific American and Electrical World . In 1881 he married Ada Mae Buchannan, by whom he had nine children, two dying in infancy. Six of Nathan's surviving children left no descendants. The seventh, Oliver (RayJack), married Priscilla Alden, who gave birth to two daughters and Nathan's only grandson, Keith Stubblefield, who would become
5777-523: The antenna wire. This meant that the full transmitter power flowed through the microphone, and even using water cooling, the power handling ability of the microphones severely limited the power of the transmissions. Ultimately only a small number of large and powerful Alexanderson alternators would be developed. However, they would be almost exclusively used for long-range radiotelegraph communication, and occasionally for radiotelephone experimentation, but were never used for general broadcasting. Almost all of
5886-633: The assertion that "while messages have been sent for distances less than ten miles, he is confident that with his machine he can talk across the Atlantic", Stubblefield made no headway in commercializing his latest invention. By now continuous-wave arc and alternator radio transmitters had been developed, which were capable of wireless telephone communication over distances that dwarfed the short ranges attainable by induction wireless systems, in addition to being able to be tuned to multiple transmitting frequencies. The invention of vacuum-tube radio transmitters in
5995-482: The audience has continued to decline. In 1987, the elimination of the Fairness Doctrine requirement meant that talk shows, which were commonly carried by AM stations, could adopt a more focused presentation on controversial topics, without the distraction of having to provide airtime for any contrasting opinions. In addition, satellite distribution made it possible for programs to be economically carried on
6104-404: The characteristics of arc-transmitters . Fessenden attempted to sell this form of radiotelephone for point-to-point communication, but was unsuccessful. Fessenden's work with high-frequency spark transmissions was only a temporary measure. His ultimate plan for creating an audio-capable transmitter was to redesign an electrical alternator , which normally produced alternating current of at most
6213-403: The commission estimated that fewer than 250 AM stations were transmitting hybrid mode signals. On October 27, 2020, the FCC voted to allow AM stations to eliminate their analog transmissions and convert to all-digital operation, with the requirement that stations making the change had to continue to make programming available over "at least one free over-the-air digital programming stream that
6322-475: 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. In countries where the use of directional antennas is common, such as the United States, transmitter sites consisting of multiple towers often occupy large tracts of land that have significantly increased in value over
6431-437: The continuous wave AM transmissions made prior to 1915 were made by versions of the arc converter transmitter, which had been initially developed by Valdemar Poulsen in 1903. Arc transmitters worked by producing a pulsating electrical arc in an enclosed hydrogen atmosphere. They were much more compact than alternator transmitters, and could operate on somewhat higher transmitting frequencies. However, they suffered from some of
6540-434: The decades, to the point that the value of land exceeds that of the station itself. This sometimes results in the sale of the transmitter site, with the station relocating to a more distant shared site using significantly less power, or completely shutting down operations. The ongoing development of alternative transmission systems, including Digital Audio Broadcasting (DAB), satellite radio, and HD (digital) radio, continued
6649-567: The decline of the popularity of the traditional broadcast technologies. These new options, including the introduction of Internet streaming, particularly resulted in the reduction of shortwave transmissions, as international broadcasters found ways to reach their audiences more easily. In 2022 it was reported that AM radio was being removed from a number of electric vehicle (EV) models, including from cars manufactured by Tesla, Audi, Porsche, BMW and Volvo, reportedly due to automakers concerns that an EV's higher electromagnetic interference can disrupt
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#17328014414426758-569: The demonstration witnesses, which stated "[Radio] Telephony is admirably adapted for transmitting news, stock quotations, music, race reports, etc. simultaneously over a city, on account of the fact that no wires are needed and a single apparatus can distribute to ten thousand subscribers as easily as to a few. It is proposed to erect stations for this purpose in the large cities here and abroad." However, other than two holiday transmissions reportedly made shortly after these demonstrations, Fessenden does not appear to have conducted any radio broadcasts for
6867-648: The expectation is that listeners will primarily be tuning into the FM signal rather than the nominally "primary" AM station. A 2020 review noted that "for many owners, keeping their AM stations on the air now is pretty much just about retaining their FM translator footprint rather than keeping the AM on the air on its own merits". In 2018 the FCC, led by then-Commission Chairman Ajit Pai , proposed greatly reducing signal protection for 50 kW Class A " clear channel " stations. This would allow co-channel secondary stations to operate with higher powers, especially at night. However,
6976-445: The fall of 1900, he successfully transmitted speech over a distance of about 1.6 kilometers (one mile), which appears to have been the first successful audio transmission using radio signals. However, at this time the sound was far too distorted to be commercially practical. For a time he continued working with more sophisticated high-frequency spark transmitters, including versions that used compressed air, which began to take on some of
7085-422: The far ends of the wire. Although most installations were around Murray, he also made sales as far away as Mississippi and Oklahoma. On February 21, 1888, Stubblefield and partner Samuel Holcomb received U.S. patent 378,183 for their "mechanical telephone" design. However, the establishment of a local Bell Telephone franchise, whose electric telephones were far superior to Stubblefield's offerings, ended most of
7194-401: The first time. Music came pouring in. Laughter came in. News came in. The world shrank, with radio. Following World War I, the number of stations providing a regular broadcasting service greatly increased, primarily due to advances in vacuum-tube technology. In response to ongoing activities, government regulators eventually codified standards for which stations could make broadcasts intended for
7303-624: The general public, for example, in the United States formal recognition of a "broadcasting service" came with the establishment of regulations effective December 1, 1921, and Canadian authorities created a separate category of "radio-telephone broadcasting stations" in April 1922. However, there were numerous cases of entertainment broadcasts being presented on a regular schedule before their formal recognition by government regulators. Some early examples include: Because most longwave radio frequencies were used for international radiotelegraph communication,
7412-417: The general public, or to have even given additional thought about the potential of a regular broadcast service, and in a 1908 article providing a comprehensive review of the potential uses for his radiotelephone invention, he made no references to broadcasting. Because there was no way to amplify electrical currents at this time, modulation was usually accomplished by a carbon microphone inserted directly in
7521-421: The general transmission of news of every description." However, the unrestricted reception of signals from Stubblefield's device meant that there was still a major limitation in its intended use for personal communication. Although he exuberantly declared: "The possibilities of the invention seem to be practically unlimited, and it will be no more than a matter of time when conversation over long distances between
7630-415: The great cities at the country will be carried on daily without wires", he also admitted: "I have as yet devised no method whereby it can be used with privacy. Wherever there is a receiving station the signal and message may be heard simultaneously. Eventually I, or some one, will discover a method of tuning the transmitting and receiving instruments so that each will answer only to its mate." At this point
7739-554: The isolation of rural life. Political officials could now speak directly to millions of citizens. One of the first to take advantage of this was American president Franklin Roosevelt , who became famous for his fireside chats during the Great Depression . However, broadcasting also provided the means to use propaganda as a powerful government tool, and contributed to the rise of fascist and communist ideologies. In
7848-411: The lack of any way to amplify the signals meant they were somewhat weak. On December 21, 1906, Fessenden made an extensive demonstration of the new alternator-transmitter at Brant Rock, Massachusetts, showing its utility for point-to-point wireless telephony, including interconnecting his stations to the wire telephone network. As part of the demonstration, speech was transmitted 18 kilometers (11 miles) to
7957-419: The late 1960s and 1970s, top 40 rock and roll stations in the U.S. and Canada such as WABC and CHUM transmitted highly processed and extended audio to 11 kHz, successfully attracting huge audiences. For young people, listening to AM broadcasts and participating in their music surveys and contests was the social media of the time. In the late 1970s, spurred by the exodus of musical programming to FM stations,
8066-399: The marketplace decide" which was best. The lack of a common standard resulted in consumer confusion and increased the complexity and cost of producing AM stereo receivers. In 1993, the FCC again revised its policy, by selecting C-QUAM as the sole AM stereo implementation. In 1993, the FCC also endorsed, although it did not make mandatory, AMAX broadcasting standards that were developed by
8175-432: The message, spreading it broadcast to receivers in all directions". However, it was recognized that this would involve significant financial issues, as that same year The Electrician also commented "did not Prof. Lodge forget that no one wants to pay for shouting to the world on a system by which it would be impossible to prevent non-subscribers from benefiting gratuitously?" On January 1, 1902, Nathan Stubblefield gave
8284-477: The mid-1910s would make possible, in the early 1920s, the nationwide broadcasting that Stubblefield had envisioned in 1902. But Stubblefield himself made no further progress beyond his previous work. Stubblefield later lived in self-imposed isolation in a crude shelter near Almo, Kentucky and died around March 28, 1928, although his body, "gnawed by rats", was not discovered until a couple days later. Although many later accounts state that he died of starvation, at
8393-448: The multiple incompatible AM stereo systems, and failure of the manufacturers (including the auto makers) to effectively promote AMAX radios, coupled with the ever-increasing background of noise in the band, the general public soon lost interest and moved on to other media. On June 8, 1988, an International Telecommunication Union (ITU)-sponsored conference held at Rio de Janeiro, Brazil adopted provisions, effective July 1, 1990, to extend
8502-537: The necessity of having to transmit a high power carrier wave to overcome ground losses, and the large antenna radiators required at the low broadcast frequencies, but can be sent over long distances via the ionosphere at night; however, they are much more susceptible to interference, and often have lower audio fidelity. Thus, AM broadcasters tend to specialize in spoken-word formats, such as talk radio , all-news radio and sports radio , with music formats primarily for FM and digital stations. People who weren't around in
8611-405: The new frequencies. It was now estimated that the expanded band could accommodate around 300 U.S. stations. However, it turned out that the number of possible station reassignments was much lower, with a 2006 accounting reporting that, out of 4,758 licensed U.S. AM stations, only 56 were now operating on the expanded band. Moreover, despite an initial requirement that by the end of five years either
8720-428: The new policy, by 2011 there were approximately 500 in operation, and as of 2020 approximately 2,800 of the 4,570 licensed AM stations were rebroadcasting on one or more FM translators. In 2009 the FCC stated that "We do not intend to allow these cross-service translators to be used as surrogates for FM stations". However, based on station slogans, especially in the case of recently adopted musical formats, in most cases
8829-411: The original station or its expanded band counterpart had to cease broadcasting, as of 2015 there were 25 cases where the original standard band station was still on the air, despite also operating as an expanded band station. HD Radio is a digital audio broadcasting method developed by iBiquity . In 2002 its "hybrid mode", which simultaneously transmits a standard analog signal as well as a digital one,
8938-433: The overheating issues of needing to insert microphones directly in the transmission antenna circuit. Vacuum tube transmitters also provided high-quality AM signals, and could operate on higher transmitting frequencies than alternator and arc transmitters. Non-governmental radio transmissions were prohibited in many countries during World War I, but AM radiotelephony technology advanced greatly due to wartime research, and after
9047-441: The primary early developer of AM technology is Canadian-born inventor Reginald Fessenden . The original spark-gap radio transmitters were impractical for transmitting audio, since they produced discontinuous pulses known as " damped waves ". Fessenden realized that what was needed was a new type of radio transmitter that produced steady "undamped" (better known as " continuous wave ") signals, which could then be "modulated" to reflect
9156-444: The process. On May 12, 1908, he was granted U.S. patent 887,357 for his new version of a wireless telephone. The patent application stated that it would be usable for "securing telephonic communications between moving vehicles and way stations". An accompanying diagram shows wireless telephony from a fixed location to passing trains, boats, and wagons. Despite receiving a patent and some financial backing from Murray residents, and
9265-747: The promoters behind the Wireless Telephone Company of America, and, in a letter dated June 19, 1902, severed his connections as a director after expressing his concern that the company was being fraudulently run. Two months later, the company announced that it had merged its operations with the Collins Wireless Telephone & Telegraph Company, a company that had been organized to promote the work of Archie Frederick Collins , who had been doing research on conductive and inductive wireless telephone systems very similar to Stubblefield's. The fanciful stock solicitations now claimed that there were plans to "license subsidiary companies in each state of
9374-650: The reception of AM transmissions and hurt the listening experience, among other reasons. However the United States Congress has introduced a bill to require all vehicles sold in the US to have an AM receiver to receive emergency broadcasts. The FM broadcast band was established in 1941 in the United States, and at the time some suggested that the AM band would soon be eliminated. In 1948 wide-band FM's inventor, Edwin H. Armstrong , predicted that "The broadcasters will set up FM stations which will parallel, carry
9483-799: The same deficiencies. The lack of any means to amplify electrical currents meant that, like the alternator transmitters, modulation was usually accomplished by a microphone inserted directly in the antenna wire, which again resulted in overheating issues, even with the use of water-cooled microphones. Thus, transmitter powers tended to be limited. The arc was also somewhat unstable, which reduced audio quality. Experimenters who used arc transmitters for their radiotelephone research included Ernst Ruhmer , Quirino Majorana , Charles "Doc" Herrold , and Lee de Forest . Advances in vacuum tube technology (called "valves" in British usage), especially after around 1915, revolutionized radio technology. Vacuum tube devices could be used to amplify electrical currents, which overcame
9592-400: The same program, as over their AM stations... eventually the day will come, of course, when we will no longer have to build receivers capable of receiving both types of transmission, and then the AM transmitters will disappear." However, FM stations actually struggled for many decades, and it was not until 1978 that FM listenership surpassed that of AM stations. Since then the AM band's share of
9701-410: The sounds being transmitted. Fessenden's basic approach was disclosed in U.S. Patent 706,737, which he applied for on May 29, 1901, and was issued the next year. It called for the use of a high-speed alternator (referred to as "an alternating-current dynamo") that generated "pure sine waves" and produced "a continuous train of radiant waves of substantially uniform strength", or, in modern terminology,
9810-481: The success of his tests. A much more ambitious demonstration was given on January 1, 1902. Assisted by his 14-year-old son, Bernard, "hundreds of people" in Murray witnessed a test where "From a station in the law office of a friend over a transmitter of his own invention [Stubblefield] gave his friends a New Year's greeting by wireless telephony, and at seven stations, located in different business houses and offices in
9919-411: The technology for AM broadcasting in stereo was challenging due to the need to limit the transmissions to a 20 kHz bandwidth, while also making the transmissions backward compatible with existing non-stereo receivers. In 1990, the FCC authorized an AM stereo standard developed by Magnavox, but two years later revised its decision to instead approve four competing implementations, saying it would "let
10028-741: The time of his death a coroner was quoted as saying "he apparently was a victim of heart disease". He was initially buried in an unmarked grave in the Bowman family cemetery in Murray, Kentucky. Although Stubblefield's inventions did not lead directly to the development of radio technology, the public demonstrations in 1902 and the extensive press coverage may have helped spur interest in the possibilities of wireless transmission of voice and music, as most prior inventors had merely sought to provide point-to-point communication, to compete with telephone and telegraph companies. Since his death, various individuals and groups in Murray, Kentucky, have promoted Murray as
10137-513: The town, the message was simultaneously delivered. Music, songs, whispered conversations could be heard with perfect ease." This in turn attracted the attention of the St. Louis Post-Dispatch , which sent a reporter to Murray to personally review Stubblefield's wireless telephone. A detailed, and positive, account appeared in the newspaper, which quoted an optimistic Stubblefield as saying that, in addition to point-to-point private communication, his system
10246-401: The translator stations are not permitted to originate programming when the "primary" AM station is broadcasting, they are permitted to do so during nighttime hours for AM stations licensed for daytime-only operation. Prior to the adoption of the new policy, as of March 18, 2009, the FCC had issued 215 Special Temporary Authority grants for FM translators relaying AM stations. After creation of
10355-406: The transmitting and receiving coils was greater than the distance between the transmitter and receiver, but the invention allowed mobility. Bernard Stubblefield reported that in 1907, using a 60-foot (18 m) coil, transmitting and receiving spanned "¼ mile (400 meters) nicely." Encountering difficulty in obtaining a patent, Nathan Stubblefield moved for a time to Washington, D.C. to speed up
10464-496: The upper end of the Region 2 AM broadcast band, by adding ten frequencies which spanned from 1610 kHz to 1700 kHz. At this time it was suggested that as many as 500 U.S. stations could be assigned to the new frequencies. On April 12, 1990, the FCC voted to begin the process of populating the expanded band, with the main priority being the reduction of interference on the existing AM band, by transferring selected stations to
10573-482: The vast savings made in cost and maintenance by the Stubblefield system, it is not unreasonable to expect that the earnings of Bell Telephone will be easily equalled by those of this company. Its stock at 25c. places the subscriber on the same basis as the earliest investors in Bell, whose profits have amounted to over 2,000%". This advertisement also stated that regional sub-companies would be established throughout
10682-548: The war the availability of tubes sparked a great increase in the number of amateur radio stations experimenting with AM transmission of news or music. Vacuum tubes remained the central technology of radio for 40 years, until transistors began to dominate in the late 1950s, and are still used in the highest power broadcast transmitters. Unlike telegraph and telephone systems, which used completely different types of equipment, most radio receivers were equally suitable for both radiotelegraph and radiotelephone reception. In 1903 and 1904
10791-404: The youngest demographic groups. Among persons aged 12–24, AM accounts for only 4% of listening, while FM accounts for 96%. Among persons aged 25–34, AM accounts for only 9% of listening, while FM accounts for 91%. The median age of listeners to the AM band is 57 years old, a full generation older than the median age of FM listeners." In 2009, the FCC made a major regulatory change, when it adopted
10900-471: Was "capable of sending simultaneous messages from a central distributing station over a very wide territory. For instance, anyone having a receiving instrument, which would consist merely of a telephone receiver and a signalling gong, could, upon being signalled by a transmitting station in Washington, or nearer, if advisable, be informed of weather news. My apparatus is capable of sending out a gong signal, as well as voice messages. Eventually, it will be used for
11009-572: Was 15 kHz resulting in bandwidth of 30 kHz. Another common limitation on AM fidelity is the result of receiver design, although some efforts have been made to improve this, notably through the AMAX standards adopted in the United States. AM broadcasts are used on several frequency bands. The allocation of these bands is governed by the ITU 's Radio Regulations and, on the national level, by each country's telecommunications administration (the FCC in
11118-474: Was approved by the FCC for use by AM stations, initially only during daytime hours, due to concerns that during the night its wider bandwidth would cause unacceptable interference to stations on adjacent frequencies. In 2007 nighttime operation was also authorized. The number of hybrid mode AM stations is not exactly known, because the FCC does not keep track of the stations employing the system, and some authorized stations have later turned it off. But as of 2020
11227-400: Was immediately recognized that, much like the telegraph had preceded the invention of the telephone, the ability to make audio radio transmissions would be a significant technical advance. Despite this knowledge, it still took two decades to perfect the technology needed to make quality audio transmissions. In addition, the telephone had rarely been used for distributing entertainment, outside of
11336-703: Was not established until the 1920s, following the development of vacuum tube receivers and transmitters. AM radio remained the dominant method of broadcasting for the next 30 years, a period called the " Golden Age of Radio ", until television broadcasting became widespread in the 1950s and received much of the programming previously carried by radio. Later, AM radio's audiences declined greatly due to competition from FM ( frequency modulation ) radio, Digital Audio Broadcasting (DAB), satellite radio , HD (digital) radio , Internet radio , music streaming services , and podcasting . Compared to FM or digital transmissions , AM transmissions are more expensive to transmit due to
11445-480: Was noted in 1884 that "with this instrument we can telephone, not only without wires, but without even a beam of light". In 1948, Murray, Kentucky's first radio station began broadcast operations, and in honor of Nathan B. Stubblefield, the owners selected WNBS as the station's call letters. In 1952, his family installed a memorial headstone at his gravesite, which credits him as the "Inventor of Wireless Telephony, or Radio". The Murray State University physics club
11554-705: Was reported in prestigious scientific publications, including Scientific American , which claimed that Stubblefield's invention would be installed by the "Gordon Telephone Company, of Charleston, S. C., for the establishment of telephonic communication between the city of Charleston and the sea islands lying off the coast of South Carolina", and Nature , which noted: "The system used is an earth-conduction one, and is, therefore, similar in principle to, though doubtless differing in detail from, many other wireless telephony systems which are being tried in various countries." In early 1902 three New York City residents, J. B. Green, W. B. Whelpley, and Wm. T. Quinn, incorporated, in
11663-473: Was the first organization to create a radio network, and also to promote commercial advertising, which it called "toll" broadcasting. Its flagship station, WEAF (now WFAN) in New York City, sold blocks of airtime to commercial sponsors that developed entertainment shows containing commercial messages . AT&T held a monopoly on quality telephone lines, and by 1924 had linked 12 stations in Eastern cities into
11772-406: Was the lack of amplifying the signals, so listeners had to use earphones , and it required the development of vacuum-tube receivers before loudspeakers could be used. The dynamic cone loudspeaker , invented in 1924, greatly improved audio frequency response over the previous horn speakers, allowing music to be reproduced with good fidelity. AM radio offered the highest sound quality available in
11881-536: Was the second of seven sons of William "Captain Billy" Jefferson Stubblefield (1830–1874), a Confederate Army veteran and lawyer, and Victoria Bowman (1837–1869), who died of scarlet fever. Stubblefield grew up in Murray, Kentucky , and his education included tutoring by a governess, followed by attendance at a boarding school in nearby Farmington called the "Male and Female Institute". His formal education ended in 1874, at
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