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116-644: The Palestine Broadcasting Service (PBS) was the state-owned radio broadcasting station that operated from Jerusalem , Mandatory Palestine (now Israel and Palestinian territories ) with the main transmitter in Ramallah . It operated from March 1936 until the end of the British Mandate of Palestine in 1948. It broadcast programs in Arabic, Hebrew, and English, with broadcasting time allotted in that order. Its Hebrew service, Kol Yerushalayim , which

232-780: A radio network that provides content in a common radio format , either in broadcast syndication or simulcast , or both. The encoding of a radio broadcast depends on whether it uses an analog or digital signal . Analog radio broadcasts use one of two types of radio wave modulation : amplitude modulation for AM radio , or frequency modulation for FM radio . Newer, digital radio stations transmit in several different digital audio standards, such as DAB ( Digital Audio Broadcasting ), HD radio , or DRM ( Digital Radio Mondiale ). The earliest radio stations were radiotelegraphy systems and did not carry audio. For audio broadcasts to be possible, electronic detection and amplification devices had to be incorporated. The thermionic valve ,

348-524: A "cascade amplifier", which eventually consisted of chaining together up to three Audions. At this time the American Telephone and Telegraph Company was researching ways to amplify telephone signals to provide better long-distance service, and it was recognized that de Forest's device had potential as a telephone line repeater. In mid-1912 an associate, John Stone Stone , contacted AT&T to arrange for de Forest to demonstrate his invention. It

464-427: A "radio station" as a government-licensed AM or FM station; an HD Radio (primary or multicast) station; an internet stream of an existing government-licensed station; one of the satellite radio channels from XM Satellite Radio or Sirius Satellite Radio ; or, potentially, a station that is not government licensed. AM stations were the earliest broadcasting stations to be developed. AM refers to amplitude modulation ,

580-561: A $ 300 per year scholarship that had been established for relatives of David de Forest. Convinced that he was destined to become a famous—and rich—inventor, and perpetually short of funds, he sought to interest companies with a series of devices and puzzles he created, and expectantly submitted essays in prize competitions, all with little success. After completing his undergraduate studies, in September 1896 de Forest began three years of postgraduate work. However, his electrical experiments had

696-597: A German, Alexander Meissner, whose application would be seized by the Office of Alien Property Custodian during World War I. The subsequent legal proceedings become divided between two groups of court cases. The first court action began in January 1920 when Armstrong, with Westinghouse, which purchased his patent, sued the De Forest Company in district court for infringement of patent 1,113,149. On May 17, 1921,

812-540: A broadcast supporting women's suffrage. More ambitious demonstrations followed. A series of tests in conjunction with the Metropolitan Opera House in New York City were conducted to determine whether it was practical to broadcast opera performances live from the stage. Tosca was performed on January 12, 1910, and the next day's test included Italian tenor Enrico Caruso . On February 24,

928-494: A business opportunity to sell advertising or subscriptions to a broader audience. This is more efficient than broadcasting to a single country, because domestic entertainment programs and information gathered by domestic news staff can be cheaply repackaged for non-domestic audiences. Governments typically have different motivations for funding international broadcasting. One clear reason is for ideological, or propaganda reasons. Many government-owned stations portray their nation in

1044-595: A co-worker who provided financial and technical help, developed variations they called "responders". A series of short-term positions followed, including three unproductive months with Professor Warren S. Johnson 's American Wireless Telegraph Company in Milwaukee, Wisconsin, and work as an assistant editor of the Western Electrician in Chicago. With radio research his main priority, de Forest next took

1160-458: A delay of ten months, in July 1913 AT&T, through a third party who disguised his link to the telephone company, purchased the wire rights to seven Audion patents for $ 50,000. De Forest had hoped for a higher payment, but was again in bad financial shape and was unable to bargain for more. In 1915, AT&T used the innovation to conduct the first transcontinental telephone calls, in conjunction with

1276-609: A fit of rage, de Forest threw it overboard—and had to be replaced by an ordinary spark coil. Even worse, the American Wireless Telephone and Telegraph Company , which claimed its ownership of Amos Dolbear 's 1886 patent for wireless communication meant it held a monopoly for all wireless communication in the United States, had also set up a powerful transmitter. None of these companies had effective tuning for their transmitters, so only one could transmit at

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1392-463: A kind of vacuum tube , was invented in 1904 by the English physicist John Ambrose Fleming . He developed a device that he called an "oscillation valve," because it passes current in only one direction. The heated filament, or cathode , was capable of thermionic emission of electrons that would flow to the plate (or anode ) when it was at a higher voltage. Electrons, however, could not pass in

1508-478: A microphone photographically onto film, using parallel lines of variable shades of gray, an approach known as "variable density", in contrast to "variable area" systems used by processes such as RCA Photophone . When the movie film was projected, the recorded information was converted back into sound, in synchronization with the picture. From October 1921 to September 1922, de Forest lived in Berlin , Germany, meeting

1624-546: A mode of broadcasting radio waves by varying the amplitude of the carrier signal in response to the amplitude of the signal to be transmitted. The medium-wave band is used worldwide for AM broadcasting. Europe also uses the long wave band. In response to the growing popularity of FM stereo radio stations in the late 1980s and early 1990s, some North American stations began broadcasting in AM stereo , though this never gained popularity and very few receivers were ever sold. The signal

1740-592: A national boundary. In other cases, a broadcast may be considered "pirate" due to the type of content, its transmission format, or the transmitting power (wattage) of the station, even if the transmission is not technically illegal (such as a webcast or an amateur radio transmission). Pirate radio stations are sometimes referred to as bootleg radio or clandestine stations. Digital radio broadcasting has emerged, first in Europe (the UK in 1995 and Germany in 1999), and later in

1856-678: A night teaching position at the Lewis Institute , which freed him to conduct experiments at the Armour Institute . By 1900, using a spark-coil transmitter and his responder receiver, de Forest expanded his transmitting range to about seven kilometers (four miles). Professor Clarence Freeman of the Armour Institute became interested in de Forest's work and developed a new type of spark transmitter. De Forest soon felt that Smythe and Freeman were holding him back, so in

1972-641: A nightly schedule featuring the Columbia recordings. These broadcasts were also used to advertise "the products of the DeForest Radio Co., mostly the radio parts, with all the zeal of our catalogue and price list", until comments by Western Electric engineers caused de Forest enough embarrassment to make him decide to eliminate the direct advertising. The station also made the first audio broadcast of election reports—in earlier elections, stations that broadcast results had used Morse code—providing news of

2088-433: A patent application which was filed on January 29, 1907, and received U.S. patent 879,532 on February 18, 1908. Because the grid-control Audion was the only configuration to become commercially valuable, the earlier versions were forgotten, and the term Audion later became synonymous with just the grid type. It later also became known as the triode. The grid Audion was the first device to amplify, albeit only slightly,

2204-511: A policy that retailers had to require their customers to return a worn-out tube before they could get a replacement. This style of business encouraged others to make and sell unlicensed vacuum tubes which did not impose a return policy. One of the boldest was Audio Tron Sales Company founded in 1915 by Elmer T. Cunningham of San Francisco, whose Audio Tron tubes cost less but were of equal or higher quality. The de Forest company sued Audio Tron Sales, eventually settling out of court. In April 1917,

2320-426: A positive, non-threatening way. This could be to encourage business investment in or tourism to the nation. Another reason is to combat a negative image produced by other nations or internal dissidents, or insurgents. Radio RSA , the broadcasting arm of the apartheid South African government, is an example of this. A third reason is to promote the ideology of the broadcaster. For example, a program on Radio Moscow from

2436-404: A practical receiver free of patent infringement. (This problem was finally resolved with the invention of the carborundum crystal detector by another company employee, General Henry Harrison Chase Dunwoody ). On November 28, 1906, in exchange for $ 1000 (half of which was claimed by an attorney) and the rights to some early Audion detector patents, de Forest turned in his stock and resigned from

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2552-622: A presentation of his work to date to the October 26, 1906, New York meeting of the American Institute of Electrical Engineers, which was reprinted in two parts in late 1907 in the Scientific American Supplement . He was insistent that a small amount of residual gas was necessary for the tubes to operate properly. However, he also admitted that "I have arrived as yet at no completely satisfactory theory as to

2668-571: A repeat of 1901—Marconi worked for the Associated Press, de Forest for the Publishers' Press Association, and the unaffiliated International Wireless Company (successor to 1901's American Wireless Telephone and Telegraph) operated a high-powered transmitter that was used primarily to drown out the other two.) Despite this setback, de Forest remained in the New York City area, in order to raise interest in his ideas and capital to replace

2784-484: A research job at the Federal Telegraph Company , which produced long-range radiotelegraph systems using high-powered Poulsen arcs . One of de Forest's areas of research at Federal Telegraph was improving the reception of signals, and he came up with the idea of strengthening the audio frequency output from a grid Audion by feeding it into a second tube for additional amplification. He called this

2900-460: A significant threat to the AM broadcasting industry. It required purchase of a special receiver. The frequencies used, 42 to 50 MHz, were not those used today. The change to the current frequencies, 88 to 108 MHz, began after the end of World War II and was to some extent imposed by AM broadcasters as an attempt to cripple what was by now realized to be a potentially serious threat. FM radio on

3016-574: A tendency to blow fuses, causing building-wide blackouts. Even after being warned to be more careful, he managed to douse the lights during an important lecture by Professor Charles S. Hastings , who responded by having de Forest expelled from Sheffield. With the outbreak of the Spanish–American War in 1898, de Forest enrolled in the Connecticut Volunteer Militia Battery as a bugler, but the war ended and he

3132-460: A time without causing mutual interference. Although an attempt was made to have the three systems avoid conflicts by rotating operations over five-minute intervals, the agreement broke down, resulting in chaos as the simultaneous transmissions clashed with each other. De Forest ruefully noted that under these conditions the only successful "wireless" communication was done by visual semaphore "wig-wag" flags. (The 1903 International Yacht races would be

3248-444: A variation that allowed him to avoid infringing on Poulsen's work. Using his "sparkless" arc transmitter, de Forest first transmitted audio across a lab room on December 31, 1906, and by February was making experimental transmissions, including music produced by Thaddeus Cahill 's telharmonium , that were heard throughout the city. On July 18, 1907, de Forest made the first ship-to-shore transmissions by radiotelephone—race reports for

3364-443: A variation, which he called the "spade detector", claiming it did not infringe on Fessenden's patents. Fessenden, and the U.S. courts, did not agree, and court injunctions enjoined American De Forest from using the device. Meanwhile, White set in motion a series of highly visible promotions for American DeForest: "Wireless Auto No.1" was positioned on Wall Street to "send stock quotes" using an unmuffled spark transmitter to loudly draw

3480-426: Is all that is necessary for a narrowband FM signal. The 200 kHz bandwidth allowed room for ±75 kHz signal deviation from the assigned frequency, plus guard bands to reduce or eliminate adjacent channel interference. The larger bandwidth allows for broadcasting a 15 kHz bandwidth audio signal plus a 38 kHz stereo "subcarrier" —a piggyback signal that rides on the main signal. Additional unused capacity

3596-642: Is capable of being developed into a really efficient detector, but in its present forms is quite unreliable and entirely too complex to be properly handled by the usual wireless operator." In May 1910, the Radio Telephone Company and its subsidiaries were reorganized as the North American Wireless Corporation, but financial difficulties meant that the company's activities had nearly come to a halt. De Forest moved to San Francisco, California, and in early 1911 took

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3712-421: Is little affected by daily changes in the ionosphere, so broadcasters need not reduce power at night to avoid interference with other transmitters. FM refers to frequency modulation , and occurs on VHF airwaves in the frequency range of 88 to 108 MHz everywhere except Japan and Russia . Russia, like the former Soviet Union , uses 65.9 to 74 MHz frequencies in addition to the world standard. Japan uses

3828-472: Is sometimes mandatory, such as in New Zealand, which uses 700 kHz spacing (previously 800 kHz). The improved fidelity made available was far in advance of the audio equipment of the 1940s, but wide interchannel spacing was chosen to take advantage of the noise-suppressing feature of wideband FM. Bandwidth of 200 kHz is not needed to accommodate an audio signal — 20 kHz to 30 kHz

3944-453: Is subject to interference from electrical storms ( lightning ) and other electromagnetic interference (EMI). One advantage of AM radio signal is that it can be detected (turned into sound) with simple equipment. If a signal is strong enough, not even a power source is needed; building an unpowered crystal radio receiver was a common childhood project in the early decades of AM broadcasting. AM broadcasts occur on North American airwaves in

4060-427: Is the automation of radio stations. Some stations now operate without direct human intervention by using entirely pre-recorded material sequenced by computer control. Lee De Forest He had over 300 patents worldwide, but also a tumultuous career – he boasted that he made, then lost, four fortunes. He was also involved in several major patent lawsuits, spent a substantial part of his income on legal bills, and

4176-515: Is the broadcasting of audio (sound), sometimes with related metadata , by radio waves to radio receivers belonging to a public audience . In terrestrial radio broadcasting the radio waves are broadcast by a land-based radio station , while in satellite radio the radio waves are broadcast by a satellite in Earth orbit. To receive the content the listener must have a broadcast radio receiver ( radio ). Stations are often affiliated with

4292-447: Is used by some broadcasters to transmit utility functions such as background music for public areas, GPS auxiliary signals, or financial market data. The AM radio problem of interference at night was addressed in a different way. At the time FM was set up, the available frequencies were far higher in the spectrum than those used for AM radio - by a factor of approximately 100. Using these frequencies meant that even at far higher power,

4408-570: The Marconi Research Centre 2MT at Writtle near Chelmsford, England . A famous broadcast from Marconi's New Street Works factory in Chelmsford was made by the famous soprano Dame Nellie Melba on June 15, 1920, where she sang two arias and her famous trill. She was the first artist of international renown to participate in direct radio broadcasts. The 2MT station began to broadcast regular entertainment in 1922. The BBC

4524-516: The medium wave frequency range of 525 to 1,705 kHz (known as the "standard broadcast band"). The band was expanded in the 1990s by adding nine channels from 1,605 to 1,705 kHz. Channels are spaced every 10 kHz in the Americas , and generally every 9 kHz everywhere else. AM transmissions cannot be ionospheric propagated during the day due to strong absorption in the D-layer of

4640-437: The regenerative circuit , and on October 6, 1914 U.S. patent 1,113,149 was issued for his discovery. U.S. patent law included a provision for challenging grants if another inventor could prove prior discovery. With an eye to increasing the value of the patent portfolio that would be sold to Western Electric in 1917, beginning in 1915 de Forest filed a series of patent applications that largely copied Armstrong's claims, in

4756-433: The "feedback circuit" and, by de Forest, as the "ultra-audion"). Beginning in 1913 Armstrong prepared papers and gave demonstrations that comprehensively documented how to employ three-element vacuum tubes in circuits that amplified signals to stronger levels than previously thought possible, and that could also generate high-power oscillations usable for radio transmission. In late 1913 Armstrong applied for patents covering

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4872-702: The 1960s to the 1980s was What is Communism? A second reason is to advance a nation's foreign policy interests and agenda by disseminating its views on international affairs or on the events in particular parts of the world. During the Cold War the American Radio Free Europe and Radio Liberty and Indian Radio AIR were founded to broadcast news from "behind the Iron Curtain " that was otherwise being censored and promote dissent and occasionally, to disseminate disinformation . Currently,

4988-593: The 76 to 90 MHz frequency band. Edwin Howard Armstrong invented wide-band FM radio in the early 1930s to overcome the problem of radio-frequency interference (RFI), which plagued AM radio reception. At the same time, greater fidelity was made possible by spacing stations further apart in the radio frequency spectrum. Instead of 10 kHz apart, as on the AM band in the US, FM channels are 200 kHz (0.2 MHz) apart. In other countries, greater spacing

5104-679: The American DeForest Wireless Telegraph Company, with himself as the company's president, and de Forest the Scientific Director. The company claimed as its goal the development of "world-wide wireless". The original "responder" receiver (also known as the "goo anti-coherer") proved to be too crude to be commercialized, and de Forest struggled to develop a non-infringing device for receiving radio signals. In 1903, Reginald Fessenden demonstrated an electrolytic detector, and de Forest developed

5220-574: The Annual Inter-Lakes Yachting Association (I-LYA) Regatta held on Lake Erie —which were sent from the steam yacht Thelma to his assistant, Frank E. Butler, located in the Fox's Dock Pavilion on South Bass Island . De Forest also interested the U.S. Navy in his radiotelephone, which placed a rush order to have 26 arc sets installed for its Great White Fleet around-the-world voyage that began in late 1907. However, at

5336-585: The Atlantic Coast and Great Lakes, and equipped shipboard stations. But the main focus was selling stock at ever more inflated prices, spurred by the construction of promotional inland stations. Most of these inland stations had no practical use and were abandoned once the local stock sales slowed. De Forest eventually came into conflict with his company's management. His main complaint was the limited support he got for conducting research, while company officials were upset with de Forest's inability to develop

5452-466: The District of Columbia district court. On May 8, 1924, that court concluded that the evidence, beginning with the 1912 notebook entry, was sufficient to establish de Forest's priority. Now on the defensive, Armstrong's side tried to overturn the decision, but these efforts, which twice went before the U.S. Supreme Court, in 1928 and 1934, were unsuccessful. This judicial ruling meant that Lee de Forest

5568-478: The Fleming valve was merely a rectifier that converted alternating current to direct current. (For this reason, de Forest objected to his Audion being referred to as "a valve".) The U.S. courts were not convinced, and ruled that the grid Audion did in fact infringe on the Fleming valve patent, now held by Marconi . In contrast, Marconi admitted that the addition of the third electrode was a patentable improvement, and

5684-509: The Manhattan Opera Company's Mme. Mariette Mazarin sang "La Habanera" from Carmen and selections from the controversial "Elektra" over a transmitter located in de Forest's lab. But these tests showed that the idea was not yet technically feasible, and de Forest would not make any additional entertainment broadcasts until late 1916, when more capable vacuum-tube equipment became available. De Forest's most famous invention

5800-464: The November 1916 Wilson-Hughes presidential election . The New York American installed a private wire and bulletins were sent out every hour. About 2,000 listeners heard The Star-Spangled Banner and other anthems, songs, and hymns. With the entry of the United States into World War I on April 6, 1917, all civilian radio stations were ordered to shut down, so 2XG was silenced for the duration of

5916-587: The Panama-Pacific International Exposition at San Francisco. Radio Telephone Company officials had engaged in some of the same stock selling excesses that had taken place at American DeForest, and as part of the U.S. government's crackdown on stock fraud, in March 1912 de Forest, plus four other company officials, were arrested and charged with "use of the mails to defraud". Their trials took place in late 1913, and while three of

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6032-474: The Tri-Ergon developers (German inventors Josef Engl (1893–1942), Hans Vogt (1890–1979), and Joseph Massolle (1889–1957)) and investigating other European sound film systems. In April 1922 he announced that he would soon have a workable sound-on-film system. On March 12, 1923, he demonstrated Phonofilm to the press; this was followed on April 12, 1923, by a private demonstration to electrical engineers at

6148-506: The U.S. Federal Communications Commission designates the 88–92 megahertz band in the U.S. for non-profit or educational programming, with advertising prohibited. In addition, formats change in popularity as time passes and technology improves. Early radio equipment only allowed program material to be broadcast in real time, known as live broadcasting. As technology for sound recording improved, an increasing proportion of broadcast programming used pre-recorded material. A current trend

6264-759: The US and Canada , just two services, XM Satellite Radio and Sirius Satellite Radio exist. Both XM and Sirius are owned by Sirius XM Satellite Radio , which was formed by the merger of XM and Sirius on July 29, 2008, whereas in Canada , XM Radio Canada and Sirius Canada remained separate companies until 2010. Worldspace in Africa and Asia, and MobaHO! in Japan and the ROK were two unsuccessful satellite radio operators which have gone out of business. Radio program formats differ by country, regulation, and markets. For instance,

6380-580: The US operates similar services aimed at Cuba ( Radio y Televisión Martí ) and the People's Republic of China , Vietnam , Laos and North Korea ( Radio Free Asia ). Besides ideological reasons, many stations are run by religious broadcasters and are used to provide religious education, religious music, or worship service programs. For example, Vatican Radio , established in 1931, broadcasts such programs. Another station, such as HCJB or Trans World Radio will carry brokered programming from evangelists. In

6496-628: The United States and Canada have chosen to use HD radio , an in-band on-channel system that puts digital broadcasts at frequencies adjacent to the analog broadcast. HD Radio is owned by a consortium of private companies that is called iBiquity . An international non-profit consortium Digital Radio Mondiale (DRM), has introduced the public domain DRM system, which is used by a relatively small number of broadcasters worldwide. Broadcasters in one country have several reasons to reach out to an audience in other countries. Commercial broadcasters may simply see

6612-589: The United States came from KDKA itself: the results of the Harding/Cox Presidential Election . The Montreal station that became CFCF began broadcast programming on May 20, 1920, and the Detroit station that became WWJ began program broadcasts beginning on August 20, 1920, although neither held a license at the time. In 1920, wireless broadcasts for entertainment began in the UK from

6728-643: The United States, France, the Netherlands, South Africa, and many other countries worldwide. The simplest system is named DAB Digital Radio, for Digital Audio Broadcasting , and uses the public domain EUREKA 147 (Band III) system. DAB is used mainly in the UK and South Africa. Germany and the Netherlands use the DAB and DAB+ systems, and France uses the L-Band system of DAB Digital Radio. The broadcasting regulators of

6844-639: The action of the oscillating and non-oscillating audion", but the organization's board refused to let him, stating that it "strongly affirms the original award". The practical effect of de Forest's victory was that his company was free to sell products that used regeneration, for during the controversy, which became more a personal feud than a business dispute, Armstrong tried to block the company from even being licensed to sell equipment under his patent. De Forest regularly responded to articles which he thought exaggerated Armstrong's contributions with animosity that continued even after Armstrong's 1954 suicide. Following

6960-533: The arc-transmitter to conduct some of the earliest experimental entertainment radio broadcasts. Eugenia Farrar sang "I Love You Truly" in an unpublicized test from his laboratory in 1907, and in 1908, on de Forest's Paris honeymoon, musical selections were broadcast from the Eiffel Tower as a part of demonstrations of the arc-transmitter. In early 1909, in what may have been the first public speech by radio, de Forest's mother-in-law, Harriot Stanton Blatch , made

7076-715: The attention of potential investors, in early 1904 two stations were established at Wei-hai-Wei on the Chinese mainland and aboard the Chinese steamer SS Haimun , which allowed war correspondent Captain Lionel James of The Times of London to report on the brewing Russo-Japanese War , and later that year a tower, with "DEFOREST" arrayed in lights, was erected on the grounds of the Louisiana Purchase Exposition in Saint Louis, Missouri, where

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7192-487: The callsign 8MK , which later became broadcasting station WWJ . In 1921, de Forest ended most of his radio research in order to concentrate on developing an optical sound-on-film process called Phonofilm . In 1919 he filed the first patent for the new system, which improved upon earlier work by Finnish inventor Eric Tigerstedt and the German partnership Tri-Ergon . Phonofilm recorded the electrical waveforms produced by

7308-728: The case of the Broadcasting Services of the Kingdom of Saudi Arabia , both governmental and religious programming is provided. Extensions of traditional radio-wave broadcasting for audio broadcasting in general include cable radio , local wire television networks , DTV radio , satellite radio , and Internet radio via streaming media on the Internet . The enormous entry costs of space-based satellite transmitters and restrictions on available radio spectrum licenses has restricted growth of Satellite radio broadcasts. In

7424-722: The college teamed up with WLOE in Boston to have students broadcast programs. By 1931, a majority of U.S. households owned at least one radio receiver . In line to ITU Radio Regulations (article1.61) each broadcasting station shall be classified by the service in which it operates permanently or temporarily. Broadcasting by radio takes several forms. These include AM and FM stations. There are several subtypes, namely commercial broadcasting , non-commercial educational (NCE) public broadcasting and non-profit varieties as well as community radio , student-run campus radio stations, and hospital radio stations can be found throughout

7540-714: The company and the Carver Corporation later cut the number of models produced before discontinuing production completely. As well as on the medium wave bands, amplitude modulation (AM) is also used on the shortwave and long wave bands. Shortwave is used largely for national broadcasters, international propaganda, or religious broadcasting organizations. Shortwave transmissions can have international or inter-continental range depending on atmospheric conditions. Long-wave AM broadcasting occurs in Europe, Asia, and Africa. The ground wave propagation at these frequencies

7656-575: The company that bore his name. American DeForest was then reorganized as the United Wireless Telegraph Company , and would be the dominant U.S. radio communications firm, albeit propped up by massive stock fraud, until its bankruptcy in 1912. De Forest moved quickly to re-establish himself as an independent inventor, working in his own laboratory in the Parker Building in New York City. The Radio Telephone Company

7772-533: The company won a gold medal for its radiotelegraph demonstrations. (Marconi withdrew from the Exposition when he learned de Forest would be there). The company's most important early contract was the construction, in 1905–1906, of five high-powered radiotelegraph stations for the U.S. Navy, located in Panama, Pensacola and Key West, Florida, Guantanamo, Cuba, and Puerto Rico. It also installed shore stations along

7888-444: The company's remaining commercial radio patent rights were sold to AT&T's Western Electric subsidiary for $ 250,000. During World War I, the Radio Telephone Company prospered from sales of radio equipment to the military. However, it also became known for the poor quality of its vacuum tubes, especially compared to those produced by major industrial manufacturers such as General Electric and Western Electric. Beginning in 1912, there

8004-576: The conclusion of the circumnavigation the sets were declared to be too unreliable to meet the Navy's needs and removed. The company set up a network of radiotelephone stations along the Atlantic coast and the Great Lakes, for coastal ship navigation. However, the installations proved unprofitable, and by 1911 the parent company and its subsidiaries were on the brink of bankruptcy. De Forest also used

8120-467: The country at night. During the night, absorption largely disappears and permits signals to travel to much more distant locations via ionospheric reflections. However, fading of the signal can be severe at night. AM radio transmitters can transmit audio frequencies up to 15 kHz (now limited to 10 kHz in the US due to FCC rules designed to reduce interference), but most receivers are only capable of reproducing frequencies up to 5 kHz or less. At

8236-458: The court ruled that the lack of awareness and understanding on de Forest's part, in addition to the fact that he had made no immediate advances beyond his initial observation, made implausible his attempt to prevail as inventor. However, a second series of court cases, which were the result of the patent office interference proceeding, had a different outcome. The interference board had also sided with Armstrong, and de Forest appealed its decision to

8352-663: The defendants were found guilty, de Forest was acquitted. With the legal problems behind him, de Forest reorganized his company as the DeForest Radio Telephone Company, and established a laboratory at 1391 Sedgewick Avenue in the Highbridge section of the Bronx in New York City. The company's limited finances were boosted by the sale, in October 1914, of the commercial Audion patent rights for radio signalling to AT&T for $ 90,000, with de Forest retaining

8468-486: The dominant medium, especially in cities. Because of its greater range, AM remained more common in rural environments. Pirate radio is illegal or non-regulated radio transmission. It is most commonly used to describe illegal broadcasting for entertainment or political purposes. Sometimes it is used for illegal two-way radio operation. Its history can be traced back to the unlicensed nature of the transmission, but historically there has been occasional use of sea vessels—fitting

8584-495: The entertainment broadcasts he had suspended in 1910, now using the superior capabilities of vacuum-tube equipment. 2XG's debut program aired on October 26, 1916, as part of an arrangement with the Columbia Graphophone Company to promote its recordings, which included "announcing the title and 'Columbia Gramophone [ sic ] Company' with each playing". Beginning November 1, the "Highbridge Station" offered

8700-604: The exact means by which the high-frequency oscillations affect so markedly the behavior of an ionized gas." In late 1906, de Forest made a breakthrough when he reconfigured the control electrode, moving it from outside the tube envelope to a position inside the tube between the filament and the plate . He called the intermediate electrode a grid , reportedly due to its similarity to the "gridiron" lines on American football playing fields. Experiments conducted with his assistant, John V. L. Hogan , convinced him that he had discovered an important new radio detector. He quickly prepared

8816-613: The fall of 1901 he made the bold decision to go to New York to compete directly with Marconi in transmitting race results for the International Yacht races. Marconi had already made arrangements to provide reports for the Associated Press , which he had successfully done for the 1899 contest. De Forest contracted to do the same for the smaller Publishers' Press Association. The race effort turned out to be an almost total failure. The Freeman transmitter broke down—in

8932-540: The flame fluctuations was due to air pressure changes produced by the loud sound of the spark. Still, he was intrigued by the idea that, properly configured, it might be possible to use a flame or something similar to detect radio signals. After determining that an open flame was too susceptible to ambient air currents, de Forest investigated whether ionized gases, heated and enclosed in a partially evacuated glass tube, could be used instead. In 1905 to 1906 he developed various configurations of glass-tube devices, which he gave

9048-453: The general name of "Audions". The first Audions had only two electrodes , and on October 25, 1906, de Forest filed a patent for the diode vacuum tube detector , that was granted U.S. patent number 841387 on January 15, 1907. Subsequently, a third "control" electrode was added, originally as a surrounding metal cylinder or a wire coiled around the outside of the glass tube. None of these initial designs worked particularly well. De Forest gave

9164-578: The high vacuum allowed it to operate at telephone-line voltages. With these changes the Audion evolved into a modern electron-discharge vacuum tube, using electron flows rather than ions. (Dr. Irving Langmuir at the General Electric Corporation made similar findings, and both he and Arnold attempted to patent the "high vacuum" construction, but the U.S. Supreme Court ruled in 1931 that this modification could not be patented). After

9280-583: The highest and lowest sidebands is quite apparent to the listener. Such distortion occurs up to frequencies of approximately 50 MHz. Higher frequencies do not reflect from the ionosphere, nor from storm clouds. Moon reflections have been used in some experiments, but require impractical power levels. The original FM radio service in the U.S. was the Yankee Network , located in New England . Regular FM broadcasting began in 1939 but did not pose

9396-458: The hopes of having the priority of the competing applications upheld by an interference hearing at the patent office. Based on a notebook entry recorded at the time, de Forest asserted that, while working on the cascade amplifier, he had stumbled on August 6, 1912, across the feedback principle, which was then used in the spring of 1913 to operate a low-powered transmitter for heterodyne reception of Federal Telegraph arc transmissions. However, there

9512-474: The ionosphere. In a crowded channel environment, this means that the power of regional channels which share a frequency must be reduced at night or directionally beamed in order to avoid interference, which reduces the potential nighttime audience. Some stations have frequencies unshared with other stations in North America; these are called clear-channel stations . Many of them can be heard across much of

9628-642: The local white citizens resented the school and its mission, and Lee spent most of his youth in Talladega isolated from the white community, with several close friends among the black children of the town. De Forest prepared for college by attending Mount Hermon Boys' School in Gill, Massachusetts , for two years, beginning in 1891. In 1893, he enrolled in a three-year course of studies at Yale University 's Sheffield Scientific School in New Haven, Connecticut, on

9744-402: The most common perception of a pirate—as broadcasting bases. Rules and regulations vary largely from country to country, but often the term pirate radio describes the unlicensed broadcast of FM radio, AM radio, or shortwave signals over a wide range. In some places, radio stations are legal where the signal is transmitted, but illegal where the signals are received—especially when the signals cross

9860-489: The new band had to begin from the ground floor. As a commercial venture, it remained a little-used audio enthusiasts' medium until the 1960s. The more prosperous AM stations, or their owners, acquired FM licenses and often broadcast the same programming on the FM station as on the AM station (" simulcasting "). The FCC limited this practice in the 1960s. By the 1980s, since almost all new radios included both AM and FM tuners, FM became

9976-601: The publication of Carl Dreher 's "E. H. Armstrong, the Hero as Inventor" in the August 1956 Harper's magazine, de Forest wrote the author, describing Armstrong as "exceedingly arrogant, brow beating, even brutal...", and defending the Supreme Court decision in his favor. In the summer of 1915, the company received an Experimental license for station 2XG , located at its Highbridge laboratory. In late 1916, de Forest renewed

10092-455: The range of a given FM signal was much shorter; thus its market was more local than for AM radio. The reception range at night is the same as in the daytime. All FM broadcast transmissions are line-of-sight, and ionospheric bounce is not viable. The much larger bandwidths, compared to AM and SSB, are more susceptible to phase dispersion. Propagation speeds are fastest in the ionosphere at the lowest sideband frequency. The celerity difference between

10208-475: The reverse direction because the plate was not heated, and thus not capable of thermionic emission of electrons. Later known as the Fleming valve , it could be used as a rectifier of alternating current, and as a radio wave detector . This greatly improved the crystal set , which rectified the radio signal using an early solid-state diode based on a crystal and a so-called cat's whisker . However, an amplifier

10324-473: The rights for sales for "amateur and experimental use". In October 1915 AT&T conducted test radio transmissions from the Navy's station in Arlington, Virginia that were heard as far away as Paris and Hawaii. The Radio Telephone Company began selling "Oscillion" power tubes to amateurs, suitable for radio transmissions. The company wanted to keep a tight hold on the tube business, and originally maintained

10440-410: The same service area. This prevents the sideband power generated by two stations from interfering with each other. Bob Carver created an AM stereo tuner employing notch filtering that demonstrated that an AM broadcast can meet or exceed the 15 kHz baseband bandwidth allotted to FM stations without objectionable interference. After several years, the tuner was discontinued. Bob Carver had left

10556-426: The small working companies that had been formed to promote his work thus far. In January 1902 he met a promoter, Abraham White, who would become de Forest's main sponsor for the next five years. White envisioned bold and expansive plans that enticed the inventor—however, he was also dishonest and much of the new enterprise would be built on wild exaggeration and stock fraud. To back de Forest's efforts, White incorporated

10672-534: The station was moved to the top of the Westinghouse factory building in East Pittsburgh, Pennsylvania . Westinghouse relaunched the station as KDKA on November 2, 1920, as the first commercially licensed radio station in the United States. The commercial broadcasting designation came from the type of broadcast license ; advertisements did not air until years later. The first licensed broadcast in

10788-415: The strength of received radio signals. However, to many observers it appeared that de Forest had done nothing more than add the grid electrode to an existing detector configuration, the Fleming valve , which also consisted of a filament and plate enclosed in an evacuated glass tube. De Forest passionately denied the similarly of the two devices, claiming his invention was a relay that amplified currents, while

10904-408: The time that AM broadcasting began in the 1920s, this provided adequate fidelity for existing microphones, 78 rpm recordings, and loudspeakers. The fidelity of sound equipment subsequently improved considerably, but the receivers did not. Reducing the bandwidth of the receivers reduces the cost of manufacturing and makes them less prone to interference. AM stations are never assigned adjacent channels in

11020-446: The title of his 1950 autobiography. In the late 1800s he became convinced there was a great future in radiotelegraphic communication (then known as " wireless telegraphy "), but Italian Guglielmo Marconi , who received his first patent in 1896, was already making impressive progress in both Europe and the United States. One drawback of Marconi's approach was his use of a coherer as a receiver, which, while providing for permanent records,

11136-447: The two sides agreed to license each other so that both could manufacture three-electrode tubes in the United States. (De Forest's European patents had lapsed because he did not have the funds needed to renew them). Because of its limited uses and the great variability in the quality of individual units, the grid Audion would be rarely used during the first half-decade after its invention. In 1908, John V. L. Hogan reported that "The Audion

11252-487: The war. The ban on civilian stations was lifted on October 1, 1919, and 2XG soon renewed operation, with the Brunswick-Balke-Collender company now supplying the phonograph records. In early 1920, de Forest moved the station's transmitter from the Bronx to Manhattan, but did not have permission to do so, so district Radio Inspector Arthur Batcheller ordered the station off the air. De Forest's response

11368-567: The world. Many stations broadcast on shortwave bands using AM technology that can be received over thousands of miles (especially at night). For example, the BBC , VOA , VOR , and Deutsche Welle have transmitted via shortwave to Africa and Asia. These broadcasts are very sensitive to atmospheric conditions and solar activity. Nielsen Audio , formerly known as Arbitron, the United States –based company that reports on radio audiences, defines

11484-672: Was a direct descendant of Jessé de Forest , the leader of a group of Walloon Huguenots who fled Europe in the 17th century due to religious persecution. De Forest's father was a Congregational Church minister who hoped his son would also become a pastor. In 1879 the elder de Forest became president of the American Missionary Association's Talladega College in Talladega, Alabama , a school "open to all of either sex, without regard to sect, race, or color", and which educated primarily African-Americans. Many of

11600-525: Was also slow (after each received Morse code dot or dash, it had to be tapped to restore operation), insensitive, and not very reliable. De Forest was determined to devise a better system, including a self-restoring detector that could receive transmissions by ear, thus making it capable of receiving weaker signals and also allowing faster Morse code sending speeds. After making unsuccessful inquiries about employment with Nikola Tesla and Marconi, de Forest struck out on his own. His first job after leaving Yale

11716-525: Was also strong evidence that de Forest was unaware of the full significance of this discovery, as shown by his lack of follow-up and continuing misunderstanding of the physics involved. In particular, it appeared that he was unaware of the potential for further development until he became familiar with Armstrong's research. De Forest was not alone in the interference determination—the patent office identified four competing claimants for its hearings, consisting of Armstrong, de Forest, General Electric's Langmuir, and

11832-530: Was amalgamated in 1922 and received a Royal Charter in 1926, making it the first national broadcaster in the world, followed by Czechoslovak Radio and other European broadcasters in 1923. Radio Argentina began regularly scheduled transmissions from the Teatro Coliseo in Buenos Aires on August 27, 1920, making its own priority claim. The station got its license on November 19, 1923. The delay

11948-513: Was carrying audio by the next year. (Herrold's station eventually became KCBS ). In The Hague, the Netherlands, PCGG started broadcasting on November 6, 1919, making it arguably the first commercial broadcasting station. In 1916, Frank Conrad , an electrical engineer employed at the Westinghouse Electric Corporation , began broadcasting from his Wilkinsburg, Pennsylvania garage with the call letters 8XK. Later,

12064-460: Was due to the lack of official Argentine licensing procedures before that date. This station continued regular broadcasting of entertainment, and cultural fare for several decades. Radio in education soon followed, and colleges across the U.S. began adding radio broadcasting courses to their curricula. Curry College in Milton, Massachusetts introduced one of the first broadcasting majors in 1932 when

12180-556: Was even tried (and acquitted) for mail fraud . Despite this, he was recognised for his pioneering work with the 1922 IEEE Medal of Honor , the 1923 Franklin Institute Elliott Cresson Medal and the 1946 American Institute of Electrical Engineers Edison Medal . Lee de Forest was born in 1873 in Council Bluffs, Iowa , the son of Anna Margaret ( née Robbins) and Henry Swift DeForest. He

12296-441: Was found that de Forest's "gassy" version of the Audion could not handle even the relatively low voltages used by telephone lines. (Owing to the way he constructed the tubes, de Forest's Audions would cease to operate with too high a vacuum.) However, careful research by Dr. Harold D. Arnold and his team at AT&T's Western Electric subsidiary determined that improving the tube's design would allow it to be more fully evacuated, and

12412-487: Was inaugurated on March 30, 1936, played an important role in the development of Hebrew as a national language for the founders of Israel. While news broadcasts and political commentary was heavily censored, the PBS' cultural programs - including its live music broadcasts - played an important role in the development of interwar Palestinian and Zionist (later Israeli) national identities. Radio station Radio broadcasting

12528-646: Was incorporated in order to promote his inventions, with James Dunlop Smith, a former American DeForest salesman, as president, and de Forest the vice president (De Forest preferred the term radio , which up to now had been primarily used in Europe, over wireless ). At the 1904 Louisiana Purchase Exposition, Valdemar Poulsen had presented a paper on an arc transmitter , which unlike the discontinuous pulses produced by spark transmitters, created steady "continuous wave" signals that could be used for amplitude modulated (AM) audio transmissions. Although Poulsen had patented his invention, de Forest claimed to have come up with

12644-406: Was increased investigation of vacuum-tube capabilities, simultaneously by numerous inventors in multiple countries, who identified additional important uses for the device. These overlapping discoveries led to complicated legal disputes over priority, perhaps the most bitter being one in the United States between de Forest and Edwin Howard Armstrong over the discovery of regeneration (also known as

12760-473: Was mustered out without ever leaving the state. He then completed his studies at Yale's Sloane Physics Laboratory, earning a Doctorate in 1899 with a dissertation on the "Reflection of Hertzian Waves from the Ends of Parallel Wires", supervised by theoretical physicist Willard Gibbs . Reflecting his pioneering work, de Forest has sometimes been credited as the "Father of Radio", an honorific which he adopted as

12876-607: Was now legally recognized in the United States as the inventor of regeneration. However, much of the engineering community continued to consider Armstrong to be the actual developer, with de Forest viewed as someone who skillfully used the patent system to get credit for an invention to which he had barely contributed. Following the 1934 Supreme Court decision, Armstrong attempted to return his Institute of Radio Engineers (present-day Institute of Electrical and Electronics Engineers ) Medal of Honor, which had been awarded to him in 1917 "in recognition of his work and publications dealing with

12992-537: Was quickly becoming viable. However, an early audio transmission that could be termed a broadcast may have occurred on Christmas Eve in 1906 by Reginald Fessenden , although this is disputed. While many early experimenters attempted to create systems similar to radiotelephone devices by which only two parties were meant to communicate, there were others who intended to transmit to larger audiences. Charles Herrold started broadcasting in California in 1909 and

13108-494: Was still required. The triode (mercury-vapor filled with a control grid) was created on March 4, 1906, by the Austrian Robert von Lieben ; independently, on October 25, 1906, Lee De Forest patented his three-element Audion . It was not put to practical use until 1912 when its amplifying ability became recognized by researchers. By about 1920, valve technology had matured to the point where radio broadcasting

13224-404: Was the "grid Audion", which was the first successful three-element ( triode ) vacuum tube , and the first device which could amplify electrical signals. He traced its inspiration to 1900, when, experimenting with a spark-gap transmitter, he briefly thought that the flickering of a nearby gas flame might be in response to electromagnetic pulses. With further tests he soon determined that the cause of

13340-595: Was to return to San Francisco in March, taking 2XG's transmitter with him. A new station, 6XC , was established as "The California Theater station", which de Forest later stated was the "first radio-telephone station devoted solely" to broadcasting to the public. Later that year a de Forest associate, Clarence "C.S." Thompson, established Radio News & Music, Inc., in order to lease de Forest radio transmitters to newspapers interested in setting up their own broadcasting stations. In August 1920, The Detroit News began operation of "The Detroit News Radiophone", initially with

13456-562: Was with the Western Electric Company 's telephone lab in Chicago, Illinois. While there he developed his first receiver, which was based on findings by two German scientists, Drs. A. Neugschwender and Emil Aschkinass . Their original design consisted of a mirror in which a narrow, moistened slit had been cut through the silvered back. Attaching a battery and telephone receiver, they could hear sound changes in response to radio signal impulses. De Forest, along with Ed Smythe,

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