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.
114-648: WPHT (1210 AM ) is a commercial radio station in Philadelphia, Pennsylvania . The station broadcasts a talk radio format and is owned by Audacy, Inc. Its studios are in Audacy's corporate headquarters on Market Street in Center City , and its transmitter and broadcast tower are on North Church Street in Moorestown, New Jersey . WPHT is a Class A clear channel station broadcasting at 50,000 watts non-directional ,
228-465: 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
342-841: 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
456-673: A Montrealer of Swiss origin, worked with SOE agents and French Resistance in Northern France before the D-Day invasion. "The group destroyed railways, bridges, troop transports and gasoline stores and hampering enemy movement and supplies," according to a CBC report. He was captured and executed by the Nazis in 1944. After the US entered the war, the OSS operated an "assassination and elimination" training program that
570-557: 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
684-918: A close confidant of Winston Churchill and Franklin Delano Roosevelt . The camp was originally designed to link Britain and the US at a time when the US was forbidden by the Neutrality Act to be directly involved in World War II. On the day before the attack on Pearl Harbor and America's entry into the war, Camp X had opened for the purpose of training Allied agents from the Special Operations Executive (SOE), Federal Bureau of Investigation (FBI), and American Office of Strategic Services (OSS) intended to be dropped behind enemy lines for clandestine missions as saboteurs and spies. However, even before
798-596: 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
912-617: 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
1026-552: 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
1140-568: 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
1254-463: 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
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#17328699397631368-786: A good radio. Programming is also available to listeners on the HD3 digital subchannel of sister station 98.1 WOGL . WPHT programming is mostly conservative talk . Weekdays, local hosts discuss a mix of national issues and news in the Delaware Valley . Weeknights, nationally syndicated programs are heard, including The Mark Levin Show and Coast to Coast AM with George Noory . On weekends, shows focus on money, health, law and real estate, some of which are paid brokered programming . Mike Opelka , Jimmy Failla, Walter Sterling and Matt Rooney host talk shows on weekend evenings. Sunday middays feature
1482-512: 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
1596-469: 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
1710-523: A local dentist. The station began its long association with CBS in 1927, when it was one of 16 charter network affiliates of the Columbia Phonographic Broadcasting System, a network airing CBS' first program on September 18, 1927. The network struggled to find advertisers, however, and William S. Paley , who had previously purchased time on the station for an entertainment program promoting his family's La Palina cigars, bought
1824-479: 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)
1938-470: A metal detector uncovered a rusty World War II smoke mortar round, triggering a visit from Canadian Forces Base Trenton 's bomb disposal team. The historic plaque erected at Intrepid Park commemorates the school, which taught the techniques of secret warfare, and Hydra, which became an essential communications centre. An adjacent plaque is dedicated to the memory of Sir William Stephenson. Camp X has been featured in movies and television programs, including
2052-503: 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
2166-399: 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
2280-482: 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
2394-423: 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
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#17328699397632508-452: 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
2622-427: 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
2736-401: A sister station to its long-time rival, KYW. With this move, the higher-rated KYW became the flagship station of CBS Radio 's Philadelphia cluster. Realizing that WGMP would never be able to compete against WIP, CBS began phasing out the sports talk shows in the summer of 1996. Finally, on August 23, the station went all-talk once again as WPTS (We're Philadelphia's Talk Station). The call sign
2850-461: 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'
2964-406: 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
3078-550: Is known today as Intrepid Park , after the code name for Sir William Stephenson , Director of British Security Co-ordination (BSC), who established the program to create the training facility. The facility was jointly operated by the Canadian military , with help from Foreign Affairs and the RCMP but commanded by the BSC; it also had close ties with MI6 . In addition to the training program,
3192-497: 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
3306-452: Is now a passive park named "Intrepid Park". In recent years, the park has been the site of annual Remembrance Day ceremonies hosted by 2 Intelligence Company , a military intelligence unit based in Toronto, Ontario. A damaged building from Camp X had been found and was being restored in 2016. Artifacts from the spy camp are still occasionally found in the park. In August 2016, a hobbyist with
3420-560: Is often stated as the location of this station, claiming that the book Inside Camp X is the source. In 2015, however, author Lynn Philip Hodgson rejected this in an interview with the Toronto Star . "Nobody knows where Station M was. You won't read where it was in any book." It is more likely, though not certain, that the Casa Loma stables housed the development and production of ASDIC sonar devices for U-boat detection. Gustave Biéler ,
3534-645: 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
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3648-492: Is unable to air due to programming conflicts. The station first began broadcasting as WCAU in May 1922. It was a 250-watt station operating out of electrician William Durham's home at 19th and Market Streets. It is Philadelphia's third-oldest radio station, having signed on two months after WIP (now WTEL ) and WFIL . In 1924, WCAU was sold to law partners Ike Levy and Daniel Murphy. Murphy later bowed out in favor of Ike's brother, Leon,
3762-556: 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
3876-615: 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
3990-479: 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
4104-585: The Record folded shortly thereafter, and its "goodwill", including the rights to buy WCAU-AM-FM, passed to the Philadelphia Bulletin , which already owned WPEN and WPEN-FM , and had secured a construction permit for WPEN-TV (channel 10). In a complex deal, the Bulletin sold off WPEN and WCAU-FM, while changing WPEN-FM's call sign to WCAU-FM and WPEN-TV's call letters to WCAU-TV . The Levys continued to run
4218-431: 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
4332-430: 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
4446-587: 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
4560-660: 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
4674-675: The 1960s, WCAU gradually began moving away from music programming, as most CBS stations. By 1967 it had become a talk station with considerable strengths in news and sports. All of Philadelphia's major professional sports teams had WCAU as their flagship radio station at one time or another. Although the station's ratings were good, in the mid-1970s, CBS made a corporate decision to move WCAU to an all-news format. All-news had earlier been established on WCBS in New York City, KNX in Los Angeles, and several other CBS AM stations. WCAU never caught up to established all-news rival KYW. By 1980, WCAU
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4788-528: 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
4902-750: The BSC and the Government of Canada . There were several names for the school: S 25-1-1 by the Royal Canadian Mounted Police (RCMP), Project-J by the Canadian military, and Special Training School No. 103 . The latter was set by the Special Operations Executive, administered under the cover of the Ministry of Economic Warfare (MEW) which operated the facility. In 1942 the Commandant of
5016-635: The British Special Operations Executive was William E. Fairbairn , called "Dangerous Dan". With instructor Eric A. Sykes , they trained numerous agents for the SOE and OSS. Fairbairn's technique was "Get down in the gutter, and win at all costs ... no more playing fair ... to kill or be killed." Another group operated Station M for developing and making covert devices for the British Security Co-ordination. Casa Loma in Toronto
5130-521: 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
5244-586: The Camp had a communications tower that could send and transmit radio and telegraph communications, called Hydra. Established December 6, 1941, the training facility closed before the end of 1944; the buildings were removed in 1969 and a monument was erected at the site. Historian Bruce Forsyth summarized the purpose of the facility: "Trainees at the camp learned sabotage techniques, subversion, intelligence gathering, lock picking, explosives training, radio communications, encode/decode, recruiting techniques for partisans,
5358-581: The Hydra signals intelligence and communications program. A series of power increases brought the station to 50,000 watts, with a new 50,000-watt transmitter dedicated October 2, 1932. The Levy brothers eventually became major stockholders in CBS, and were members of the network's board for many years. On December 26, 1932, WCAU moved to a new facility at 1622 Chestnut Street. Broadcasting magazine called it "a thoroughly modern 9-story building ... erected especially for
5472-411: 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
5586-423: The U.S. The camp was an appropriate location for the safe transfer of code due to the topography of the land; it was also an excellent site for picking up radio signals from the United Kingdom. A news article also indicates that "HAM Operators at Camp X used transmitters to send and receive coded messages from Britain behind enemy lines". Hydra sent and received Allied radio (including telegraph) signals from around
5700-477: The U.S., for example) subject to international agreements. Camp X Camp X was the unofficial name of the secret Special Training School No. 103 , a Second World War British paramilitary installation for training covert agents in the methods required for success in clandestine operations. It was located on the northwestern shore of Lake Ontario between Whitby and Oshawa in Ontario , Canada. The area
5814-662: 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
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#17328699397635928-514: The United States entered the war on December 8, 1941, agents from America's intelligence services expressed an interest in sending personnel for training at the soon to be opened Camp X. Agents from the FBI and the OSS (forerunner of the Central Intelligence Agency , or CIA) secretly attended Camp X in early 1942; at least a dozen attended at least some training. After Stephenson established
6042-532: The WCAU Broadcasting Co." The building included eight studios and "a special office for Leopold Stokowski, director of the Philadelphia Orchestra". WCAU began experimenting with an FM station in 1942 and it was licensed in 1943. The call sign in its early years was WCAU-FM and it broadcast at 102.9 MHz. The Levys agreed to sell WCAU-AM-FM to The Philadelphia Record in 1946. However,
6156-523: 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
6270-426: The art of silent killing and unarmed combat." Communication training, including Morse code , was also provided. The existence of the camp was kept such a secret that even Canadian Prime Minister William Lyon Mackenzie King was unaware of its full purpose. Camp X was established December 6, 1941, by the chief of British Security Co-ordination (BSC), Sir William Stephenson , a Canadian from Winnipeg , Manitoba and
6384-474: 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
6498-787: The camp was Lieutenant Colonel R. M. Brooker of the British Army. In addition to operating an excellent document forging facility, Camp X trained numerous Allied covert operatives. An estimate published by the CBC states that "By war's end, between 500 and 2,000 Allied agents had been trained (figures vary) and sent abroad..." behind enemy lines. Reports indicate that graduates worked as "secret agents, security personnel, intelligence officers, or psychological warfare experts, serving in clandestine operations". Many were captured, tortured, and executed; survivors received no individual recognition for their efforts." The predominant close-combat trainer for
6612-404: 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
6726-403: 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
6840-475: 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
6954-437: 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
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#17328699397637068-583: The country and wanted to add the CBS stations to its portfolio. The merger was approved on November 9, 2017, and was consummated on the 17th. In 2021, Entercom changed its name to Audacy, Inc. In 2020, WPHT host Ken Matthews was named one of the 100 most important talk radio show hosts (the "Heavy Hundred") in America by TALKERS Magazine . ** = Audacy operates pursuant to a local marketing agreement with Martz Communications Group . AM broadcasting The earliest experimental AM transmissions began in
7182-636: The country. Gouzenko and his family spent two years at the facility. Later, until the buildings were destroyed in 1969, the camp became the Oshawa Wireless Station under operation by the Royal Canadian Corps of Signals as a secret listening location. Any records not previously destroyed were stored under the Official Secrets Act . The site, located on Boundary Road in Whitby, Ontario ,
7296-434: 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
7410-567: 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
7524-569: 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
7638-756: The early 1900s. However, widespread AM broadcasting 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
7752-645: 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,
7866-419: The facility and acted as the Camp's first head, the first commandant was Lt. Col. Arthur Terence Roper-Caldbeck. Colonel William "Wild Bill" Donovan , war-time head of the OSS, credited Stephenson with teaching Americans about foreign intelligence gathering. The CIA even named their recruit training facility "The Farm", a nod to the original farm that existed at the Camp X site. Camp X was jointly operated by
7980-445: 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
8094-401: 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
8208-620: 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,
8322-417: 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
8436-541: 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
8550-411: 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
8664-419: 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,
8778-494: The long-running Sounds of Sinatra with Sid Mark . Some hours begin with an update from CBS News Radio . Weather is supplied by Channel 6 WPVI-TV . WPHT airs Temple University football and men's basketball. It also carries some Penn State Nittany Lions games. WPHT was the flagship station for Philadelphia Phillies baseball for 32 years, until the 2016 season, when co-owned 94.1 WIP-FM took over that role. However, WPHT still carries any Phillies games that WIP-FM
8892-399: 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
9006-573: The maximum for commercial AM stations. It is one of two clear-channel stations in Philadelphia, the other being sister station KYW . Its signal covers the Philadelphia metropolitan area and much of the Lehigh Valley region of eastern Pennsylvania and parts of New Jersey , Delaware , and Maryland . At night, it can be received in much of the Eastern United States and Eastern Canada with
9120-432: 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
9234-448: 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
9348-537: 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
9462-583: The network with $ 500,000 of his family's money and renamed it the Columbia Broadcasting System. Actor Paul Douglas began his career at WCAU, where he worked as an announcer and sportscaster from 1928 to 1934. In 1930, WCAU initiated a shortwave radio service, operating under the call sign W3XAU. It is believed that this was the first license issued by the FCC for a commercial international shortwave broadcast station. Initially W3XAU simulcast WCAU programming, but eventually original programming
9576-405: 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
9690-428: 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
9804-411: 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,
9918-433: 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
10032-441: 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
10146-592: 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
10260-799: 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
10374-400: 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
10488-410: 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,
10602-542: The stations while serving as consultants to the Bulletin, and it was largely due to their influence that WCAU-TV took to the air on May 23, 1948, as a CBS affiliate. The stations moved to a new studio in Bala Cynwyd in 1952. In 1957, the Bulletin sold WCAU-AM-FM-TV to CBS. This came because the Bulletin had recently bought WGBI-TV in Scranton, Pennsylvania and changed its call sign to WDAU-TV to complement WCAU. However,
10716-411: 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
10830-401: 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
10944-413: The two television stations' signals overlapped so much that it constituted a duopoly under Federal Communications Commission (FCC) rules of the time. CBS had to get a waiver to keep its new Philadelphia cluster. In addition to significant overlap of the television stations' grade B signals, the FCC normally did not allow common ownership of clear channel stations with overlapping nighttime signals. In
11058-492: 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
11172-548: 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
11286-611: The world. The Government of Canada later stated that Hydra provided "an essential tactical and strategic component of the larger Allied radio network, secret information was transmitted securely to and from Canada, Great Britain, other Commonwealth countries and the United States". The Hydra station was valuable for both coding and decoding information in relative safety from the prying ears of German radio observers and Nazi detection. Hydra also had direct access via land lines to Ottawa , New York City and Washington, D.C. for telegraph and telephone communications. The main transmitter
11400-404: 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
11514-518: Was "a highly romanticised version of the true spy" William Stephenson , and what Fleming once learned from him. Children's book writer Roald Dahl and British screenwriter Paul Dehn also trained at the camp. After it had closed in the fall of 1945, Camp X was used by the RCMP as a secure location for interviewing Soviet embassy cypher-clerk Igor Gouzenko , who had defected to Canada on 5 September and revealed an extensive Soviet espionage operation in
11628-565: 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
11742-474: 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
11856-410: Was changed again less than a month later to the current WPHT to avoid confusion with nearby Trenton, New Jersey 's WPST . Only a year later, WIP became a sister station to WPHT when CBS merged with its owner, Infinity Broadcasting Corporation , which was then part of Viacom . On February 2, 2017, CBS Radio announced it would merge with Entercom . Entercom already owned numerous radio stations around
11970-532: Was created specifically for international listeners. W3XAU, later WCAI, then WCAB, was closed down in 1941 as CBS consolidated various shortwave operations. The 10 kW shortwave transmitter was disassembled, and WCAU staff were told that it was sent to England to aid the BBC war propaganda efforts. However, the transmitter was actually sent to Camp X , a secret World War II paramilitary and commando training facility located near Toronto , Ontario, Canada, becoming part of
12084-530: Was dubbed "the school of mayhem and murder" by George Hunter White. William Donovan later started similar programs in Maryland and Virginia, as well as in Cairo, Egypt. The Virginia Quantico training center was initially based on Camp X programs. One of the unique features of Camp X was Hydra , a highly sophisticated telecommunications relay station established in May 1942 by engineer Benjamin deForest Bayly . Bayly
12198-400: 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
12312-450: Was making moves to reclaim its heritage as a talk and sports leader. However, 96.5 WWDB-FM had established itself as a strong talk station, and WCAU struggled for years to attract listeners and establish a consistent image. On August 15, 1990, CBS abruptly changed the WCAU call sign after 68 years, becoming WOGL. It dropped the talk format in favor of oldies of the 1950s, 1960s and 1970s. It
12426-479: Was partially simulcast with its FM sister station, by then WOGL-FM . In 1993, the AM station began running sports talk after 7 pm. The station went all-sports as WGMP (The Game) on March 18, 1994. However, once again, the station was taking on an entrenched competitor, WIP , and WGMP's largely syndicated program lineup won few listeners away from WIP's heavily local schedule. A year later, CBS merged with Westinghouse Electric Corporation , thus making 1210 AM
12540-509: Was previously used as that of American AM station WCAU 's shortwave sibling W3XAU, and upon severance of W3XAU in 1941, the transmitter was refurbished and became the transmitter for Hydra. Other radio apparatus was purchased discreetly from amateur radio enthusiasts, brought to the building in pieces and assembled on site. After use by the Canadian Forces during the Cold War, the transmitter
12654-437: Was scrapped in 1969. One of the trainees, or at least a visitor, may have been Ian Fleming , later famous for his James Bond books, according to the book Inside Camp X by Lynn Philip Hodgson. (While in Toronto, Fleming stayed at a hotel near St. James-Bond United Church , but many believe the name was borrowed from a noted American ornithologist.) There is however evidence against this claim. The character of James Bond
12768-492: Was the assistant director, with British army rank of lieutenant colonel. He also invented a very fast offline, one-time tape cipher machine for coding/decoding telegraph transmissions labelled the Rockex or "Telekrypton". The book Inside Camp X indicates that the facility was located on Lake Ontario , 30 miles across from the U.S., because it was an ideal location for receiving radio communications from Europe and South America via
12882-468: 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
12996-406: 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
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