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60-575: The word "treatise" has its origins in the early 14th century, derived from the Anglo-French term tretiz , which itself comes from the Old French traitis , meaning "treatise" or "account." This Old French term is rooted in the verb traitier , which means "to deal with" or "to set forth in speech or writing". The etymological lineage can be traced further back to the Latin word tractatus , which

120-427: 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 ,

180-494: 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

240-463: 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

300-546: 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

360-592: 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

420-426: 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

480-460: 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

540-495: Is a form of the verb tractare , meaning "to handle," "to manage," or "to deal with". The Latin roots suggest a connotation of engaging with or discussing a subject in depth, which aligns with the modern understanding of a treatise as a formal and systematic written discourse on a specific topic. The works presented here have been identified as influential by scholars on the development of human civilization. Euclid's Elements has appeared in more editions than any other books except

600-426: 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

660-670: Is known that Theon edited the Elements of Euclid . He may also have edited some other works by Euclid and Ptolemy , although here the evidence is less certain. The editions ascribed to Theon are: Of his commentaries, those which are extant are: Among Theon's lost works, the Suda mentions On Signs and Observation of Birds and the Sound of Crows ; On the Rising of the Dog[-Star] ; and On

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720-421: 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

780-531: Is said to have lived during the reign of Theodosius I (379–395). The Suda , a tenth-century Byzantine encyclopedia, calls Theon a "man of the Mouseion ". However, both the Library of Alexandria and the original Mouseion were destroyed in the first century BC and according to classical historian Edward J. Watts, Theon was probably the head of a school called the "Mouseion", which was named in emulation of

840-472: 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

900-453: 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

960-447: 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,

1020-702: The Bible and is one of the most important mathematical treatises ever. It has been translated to numerous languages and remains continuously in print since the beginning of printing. Before the invention of the printing press, it was manually copied and widely circulated. When scholars recognized its excellence, they removed inferior works from circulation in its favor. Many subsequent authors, such as Theon of Alexandria , made their own editions, with alterations, comments, and new theorems or lemmas. Many mathematicians were influenced and inspired by Euclid's masterpiece. For example, Archimedes of Syracuse and Apollonius of Perga ,

1080-605: The Hellenistic Mouseion that had once included the Library of Alexandria, but which had little other connection to it. Theon's school was exclusive, highly prestigious, and doctrinally conservative. Neither Theon nor his daughter Hypatia seems to have had any connections to the militant Iamblichean Neoplatonists who taught in the Serapeum of Alexandria and instead preferred Plotinian neoplatonism . Theon

1140-570: 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

1200-516: 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

1260-702: 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,

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1320-593: 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

1380-598: The Inundation of the Nile . Radio broadcasting Radio broadcasting 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

1440-506: 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

1500-759: 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,

1560-580: 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

1620-691: 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

1680-589: 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

1740-643: 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

1800-728: 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

1860-722: 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

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1920-714: 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

1980-891: The content the listener must have a broadcast radio receiver ( radio ). Stations are often affiliated with 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 ,

2040-467: 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

2100-486: 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

2160-516: The geometry of three-dimensional objects such as polyhedra), number theory, and the theory of proportions. It was essentially a compilation of all mathematics known to the Greeks up until Euclid's time. Drawing on the work of his predecessors, especially the experimental research of Michael Faraday , the analogy with heat flow by William Thomson (later Lord Kelvin) and the mathematical analysis of George Green , James Clerk Maxwell synthesized all that

2220-427: The greatest mathematicians of their time, received their training from Euclid's students and his Elements and were able to solve many open problems at the time of Euclid. It is a prime example of how to write a text in pure mathematics, featuring simple and logical axioms, precise definitions, clearly stated theorems, and logical deductive proofs. The Elements consists of thirteen books dealing with geometry (including

2280-583: 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

2340-474: 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

2400-402: 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

2460-489: 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

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2520-460: The phenomenon of light dispersion where other models failed. John William Strutt (Lord Rayleigh) and Josiah Willard Gibbs then proved that the optical equations derived from Maxwell's theory are the only self-consistent description of the reflection, refraction, and dispersion of light consistent with experimental results. Optics thus found a new foundation in electromagnetism . Hertz's experimental work in electromagnetism stimulated interest in

2580-522: The possibility of wireless communication, which did not require long and expensive cables and was faster than even the telegraph. Guglielmo Marconi adapted Hertz's equipment for this purpose in the 1890s. He achieved the first international wireless transmission between England and France in 1900 and by the following year, he succeeded in sending messages in Morse code across the Atlantic. Seeing its value,

2640-455: 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

2700-475: 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

2760-410: 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

2820-472: The shipping industry adopted this technology at once. Radio broadcasting became extremely popular in the twentieth century and remains in common use in the early twenty-first. But it was Oliver Heaviside , an enthusiastic supporter of Maxwell's electromagnetic theory, who deserves most of the credit for shaping how people understood and applied Maxwell's work for decades to come; he was responsible for considerable progress in electrical telegraphy, telephony, and

2880-534: 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

2940-451: The study of the propagation of electromagnetic waves. Independent of Gibbs, Heaviside assembled a set of mathematical tools known as vector calculus to replace the quaternions , which were in vogue at the time but which Heaviside dismissed as "antiphysical and unnatural." Theon of Alexandria Theon of Alexandria ( / ˌ θ iː ə n , - ɒ n / ; Ancient Greek : Θέων ὁ Ἀλεξανδρεύς ; c.  AD 335  – c.  405 )

3000-408: 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

3060-567: 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

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3120-466: Was a Greek scholar and mathematician who lived in Alexandria , Egypt . He edited and arranged Euclid 's Elements and wrote commentaries on works by Euclid and Ptolemy . His daughter Hypatia also won fame as a mathematician. Little is known about the life of Theon. He made predictions and observations of solar and lunar eclipses in 364 which show he was active at that time, and he

3180-530: 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

3240-513: 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,

3300-422: Was confirmed by Heinrich Hertz . In the process, Hertz generated and detected what are now called radio waves and built crude radio antennas and the predecessors of satellite dishes. Hendrik Lorentz derived, using suitable boundary conditions, Fresnel's equations for the reflection and transmission of light in different media from Maxwell's equations. He also showed that Maxwell's theory succeeded in illuminating

3360-460: 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

3420-552: Was known about electricity and magnetism into a single mathematical framework, Maxwell's equations . Originally, there were 20 equations in total. In his Treatise on Electricity and Magnetism (1873), Maxwell reduced them to eight. Maxwell used his equations to predict the existence of electromagnetic waves, which travel at the speed of light. In other words, light is but one kind of electromagnetic wave. Maxwell's theory predicted there ought to be other types, with different frequencies. After some ingenious experiments, Maxwell's prediction

3480-537: 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

3540-494: 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

3600-570: Was the father of the mathematician Hypatia , who succeeded him as head of his school Theon dedicated his commentary on the Almagest to a boy named Epiphanius, who may have been his son. Also, in his commentary on the Almagest he states that his daughter Hypatia contributed to Book III of the Almagest stating "the edition having been prepared by the philosopher, my daughter Hypatia." A lunar crater, Theon Junior , now bears Theon's name. It

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