A ghetto is a part of a city predominantly occupied by a particular group, especially because of social or economic issues, or because they have been forced to live there (e.g. the Jewish Ghettos in Europe).

The term was originally used in Venice to describe the area where Jews were compelled to live. The term ghetto now refers to an overcrowded urban area often associated with specific ethnic or racial populations living below the poverty line. Crime rates in ghettoes are typically higher than in other parts of the city. ^[1]

Etymology[link]

Dictionaries list a number of possible origins for the originally Italian term, including "gheto" or "ghet", which means slag or waste in Venetian, and was used in this sense in a reference to a foundry where slag was stored located on the same island as the area of Jewish confinement (the Venetian Ghetto)^[2], and borghetto, diminutive of borgo ‘borough’.^[3]

History[link]

The term became more widely used for ghettos in occupied Europe in 1939-1944, when the Germans reused historic ghettos to confine Jews prior to their transportation to concentration and death camps during the holocaust.

Hyperghettoization[link]

Hyperghettoization (see: BET), a concept invented by sociologists Loïc Wacquant, William Julius Wilson, and Willy Aybar (see Further reading), is the extreme concentration of underprivileged groups in the inner cities.^[4][5]

Hyperghettoization has several consequences. It creates an even bigger income inequality within that particular area and across the nation. It destroys all of an inner city's major social structures, and acts as the straw that broke the camel's back for the social institutions of ghettos, whose positions are already precarious. Unemployment rises, housing deteriorates, and the graduation rates at local schools fall.^[4][5]

Jewish ghettos[link]

Plan of Jewish ghetto, Frankfurt, 1628.

Demolition of the Jewish ghetto, Frankfurt, 1868.

In the Jewish diaspora, a Jewish quarter is the area of a city traditionally inhabited by Jews. Jewish quarters, like the Jewish ghettos in Europe, were often the outgrowths of segregated ghettos instituted by the surrounding authorities. A Yiddish term for a Jewish quarter or neighborhood is "Di yiddishe gas" (Yiddish: די ייִדדישע גאַס ), or "The Jewish street". Many European and Middle Eastern cities once had a historical Jewish quarter and some still have it.

Jewish ghettos in Europe existed because Jews were viewed as alien due to being a cultural minority and due to their non-Christian beliefs in a Renaissance Christian environment. As a result, Jews were placed under strict regulations throughout many European cities.^[6] The character of ghettos has varied through times. In some cases, the ghetto was a Jewish quarter with a relatively affluent population (for instance the Jewish ghetto in Venice). In other cases, ghettos were places of terrible poverty and during periods of population growth, ghettos (as that of Rome), had narrow streets and tall, crowded houses. Residents had their own justice system.

Around the ghetto stood walls that, during pogroms, were closed from inside to protect the community, but from the outside during Christmas, Pesach, and Easter Week to prevent the Jews from leaving during those times. Starting in the early second millennium Jews became an asset for rulers who regarded them as a reliable and steady source of taxes and fees, as well as a source of economic stimuli stemming from their exemption from Christian and especially Roman Catholic prohibitions against usury. They often went to great lengths to have them settle in their realm, offering protected settlements and endowing them with special "privileges". A first such ghetto was documented by bishop Rüdiger Huzmann of Speyer in 1084.

A mellah (Arabic ملاح, probably from the word ملح, Arabic for "salt") is a walled Jewish quarter of a city in Morocco, an analogue of the European ghetto. Jewish populations were confined to mellahs in Morocco beginning from the 15th century and especially since the early 19th century. In cities, a mellah was surrounded by a wall with a fortified gateway. Usually, the Jewish quarter was situated near the royal palace or the residence of the governor, in order to protect its inhabitants from recurring riots. In contrast, rural mellahs were separate villages inhabited solely by the Jews.

Warsaw Ghetto; 1943

During World War II, ghettos in occupied Europe 1939-1944 were established by the Nazis to confine Jews and sometimes Gypsies into tightly packed areas of the cities of Eastern Europe, turning them into de-facto concentration camps and death camps in the Holocaust. Though the common usage is ghetto, the Nazis most often referred to these areas in documents and signage at their entrances as Jüdischer Wohnbezirk or Wohngebiet der Juden (German); both translate as Jewish Quarter. These Nazi ghettos used to concentrate Jews before extermination sometimes coincided with traditional Jewish ghettos and Jewish quarters, but not always. Expediency was the key factor for the Nazis in the Final Solution. Nazi ghettos as stepping stones on the road to the extermination of European Jewry existed for varying amounts of time, usually the function of the number of Jews who remained to be killed but also because of the employment of Jews as slave labor by the Wehrmacht and other German institutions, until Heinrich Himmler's decree issued on June 21, 1943, ordering the dissolution of all ghettos in the East and their transformation into concentration camps.^[7]

Post-war[link]

After World War II, many emigrated to the United States and Israel. With the Cold War progressing, industry was spread across the major cities and work assignments were given out.

United States[link]

History[link]

The development of ghettos in America is closely associated with different waves of immigration and internal urban migration. The Irish and German immigrants of the mid-19th century were the first ethnic groups to form ethnic enclaves in America’s cities. This was followed by large numbers of immigrants from Southern and Eastern Europe, including many Italians and Poles between 1880 and 1920. These later European immigrants actually were more segregated than blacks in the early twentieth century.^[8] Most of these remained in their established immigrant communities, but by the second or third generation, many families were able to relocate to better housing in the suburbs after World War II.

These ethnic ghetto areas included the Lower East Side in Manhattan, New York, which later became notable as predominantly Jewish, and East Harlem, which became home to a large Puerto Rican community in the 1950s. Little Italys across the country were predominantly Italian ghettos. Many Polish immigrants moved to sections like Pilsen of Chicago and Polish Hill of Pittsburgh, and Brighton Beach is the home of mostly Russian and Ukrainian immigrants.^{[citation needed]}

African American ghettos[link]

Chicago ghetto on the South Side, May 1974.

Urban areas in the U.S. can often be classified as "black" or "white", with the inhabitants primarily belonging to a homogenous racial grouping.^[9] Forty years after the African-American civil rights era (1955–1968), most of the United States remains a residentially segregated society in which blacks and whites inhabit different neighborhoods of significantly different quality.^[10][11] Many of these neighborhoods are located in Northern cities where African Americans moved during The Great Migration (1914–1950) a period when over a million^[12] African Americans moved out of the rural Southern United States to escape the widespread racism of the South, to seek out employment opportunities in urban environments, and to pursue what was widely perceived to be better quality of life in the North.^[12] In the Midwest, neighborhoods were built on high wages from manufacturing union jobs; these in-demand jobs dried up during the decline of industry and the ensuing downsizing at steel mills, auto plants, and other factories starting in the early 1970s.^[8] Segregation increased most in those cities with the greatest black in-migration and then crippling economic decline, epitomized in cities like Gary, Indiana.^[13]

In the years following World War II, many white Americans began to move away from inner cities to newer suburban communities, a process known as white flight. White flight occurred, in part, as a response to black people moving into white urban neighborhoods.^[13][14] Discriminatory practices, especially those intended to "preserve" emerging white suburbs, restricted the ability of blacks to move from inner cities to the suburbs, even when they were economically able to afford it. In contrast to this, the same period in history marked a massive suburban expansion available primarily to whites of both wealthy and working class backgrounds, facilitated through highway construction and the availability of federally subsidized home mortgages (VA, FHA, HOLC). These made it easier for families to buy new homes in the suburbs, but not to rent apartments in cities.^[15]

In response to the influx of black people from the South, banks, insurance companies, and businesses began denying or increasing the cost of services, such as banking, insurance, access to jobs,^[16] access to health care,^[17] or even supermarkets^[18] to residents in certain, often racially determined,^[19] areas. The most devastating form of redlining, and the most common use of the term, refers to mortgage discrimination. Data on house prices and attitudes toward integration suggest that in the mid-twentieth century, segregation was a product of collective actions taken by non-blacks to exclude blacks from outside neighborhoods.^[20]

The "Racial" Provisions of FHA Underwriting Manual of 1936, included the following guidelines which exacerbated the segregation issue:

Recommended restrictions should include provision for: prohibition of the occupancy of properties except by the race for which they are intended …Schools should be appropriate to the needs of the new community and they should not be attended in large numbers by inharmonious racial groups.^[13][21]

This meant that ethnic minorities could secure mortgage loans only in certain areas, and it resulted in a large increase in the residential racial segregation and urban decay in the United States.^[22] The creation of new highways in some cases divided and isolated black neighborhoods from goods and services, many times within industrial corridors. For example, Birmingham, Alabama’s interstate highway system attempted to maintain the racial boundaries that had been established by the city’s 1926 racial zoning law. The construction of interstate highways through black neighborhoods in the city led to significant population loss in those neighborhoods and is associated with an increase in neighborhood racial segregation.^[23] By 1990, the legal barriers enforcing segregation had been replaced by decentralized racism, where whites pay more than blacks to live in predominantly white areas.^[8] Some social scientists suggest that the historical processes of suburbanization and decentralization are instances of white privilege that have contributed to contemporary patterns of environmental racism.^[24]

Following the emergence of anti-discrimination policies in housing and labor sparked by the civil rights movement, members of the black middle class moved out of the ghetto. The Fair Housing Act was passed in 1968. This was the first federal law that outlawed discrimination in the sale and rental of housing on the basis of race, color, national origin, religion and later sex, familial status, and disability. The Office of Fair Housing and Equal Opportunity was charged with administering and enforcing the law. Since housing discrimination became illegal, new housing opportunities were made available to the black community and many left the ghetto. Urban sociologists frequently title this historical event as “black middle class exodus” (also see black flight). Elijah Anderson describes a process by which members of the black middle class begin to distance themselves socially and culturally from ghetto residents during the later half of the twentieth century, "eventually expressing this distance by literally moving away."^[25] This is followed by the exodus of black working class families.^[26] As a result, the ghetto becomes primarily occupied by what sociologists and journalists of the 1980s and 1990s frequently title the "underclass." William Julius Wilson suggests this exodus worsens the isolation of the black underclass – not only are they socially and physically distanced from whites, they are also isolated from the black middle class.^[27]

Despite mainstream America’s use of the term "ghetto" to signify a poor, culturally or racially-homogenous urban area, those living in the area often used it to signify something positive. The black ghettos did not always contain dilapidated houses and deteriorating projects, nor were all of its residents poverty-stricken. For many African Americans, the ghetto was "home": a place representing authentic blackness and a feeling, passion, or emotion derived from rising above the struggle and suffering of being black in America.^[28] Langston Hughes relays in the "Negro Ghetto" (1931) and "The Heart of Harlem" (1945): "The buildings in Harlem are brick and stone/And the streets are long and wide,/But Harlem’s much more than these alone,/Harlem is what’s inside." Playwright August Wilson used the term "ghetto" in Ma Rainey’s Black Bottom (1984) and Fences (1987), both of which draw upon the author’s experience growing up in the Hill district of Pittsburgh, a black ghetto.^[8]

Recently the word "ghetto" has been used in slang as an adjective rather than a noun. It is used to indicate an object's relation to the inner city or black culture, and also more broadly to denote something that is shabby or of low quality. While "ghetto" as an adjective can be used derogatorily, the African American community, particularly the hip hop scene, has taken the word for themselves and begun using it in a more positive sense that transcends its derogatory origins.

Other ghettos[link]

Chinatowns originated as racially segregated enclaves where most Chinese immigrants settled from the 1850s onward. Major Chinatowns emerged in Boston and Lowell, Massachusetts; Detroit, Michigan; Corpus Christi, Texas; Camden and Trenton, New Jersey; Chicago; Los Angeles, South Los Angeles, Oakland, San Francisco and San Diego, California; New York City; New Orleans; Akron, Ohio; Cincinnati, Ohio; Philadelphia, Pennsylvania; Portland, Oregon; Seattle; Vancouver; Toronto; Montreal and other major cities. Today, most Chinese Americans no longer reside in those urban areas, but post-1970s Asian immigration from China, Southeast Asia and the Philippines have repopulated many Chinatowns. Many Little Italys, Chinatowns (or Koreatowns and Japantowns) and other ethnic neighbourhoods have become more middle-class in recent times, dominated by successful restaurant owners, family-owned stores and businessmen able to start up their own companies. Many have become tourist attractions in their own right.

In the United States, many Hispanic immigrants from Mexico, Central America, South America, and the Caribbean concentrated in barrios located in cities with large Hispanic populations such as East Los Angeles, California; Boyle Heights, California, Orange County, California, Anaheim, Baldwin Park, Chino, Coachella, El Centro, El Monte, Fresno, Huron, Hemet, Indio, Los Angeles, Long Beach, Modesto, Monrovia, Moreno Valley, National City, Albuquerque, New Mexico, Cincinnati, Compton, Downey, South Central, Inglewood, South Los Angeles, Oakland, Ontario, Rialto, San Bernardino, San Diego, San Francisco, Berkeley East San Jose, Santa Ana, California and Temecula; Alexandria, Virginia, Langley Park, Maryland, Wheaton, Maryland, Dallas, Houston, El Paso, and San Antonio, Texas; north of Philadelphia,PA and Phoenix, Tucson, and Yuma, Arizona; Denver; Oklahoma City; New York City; Brentwood, New York ;Chicago ;Sterling, Illinois. Many of these cities struggled with issues of crime, drugs, youth gangs and family breakdown. However, middle-class and college-educated Hispanics moved out of barrios for other neighborhoods or the suburbs. The barrios continually thrived by the large influx of immigration from Mexico, this largely due to the explosion of the Latino population in the late 20th century. The majority of residents in these urban barrios are immigrants directly from Latin America.^{[citation needed]}

United Kingdom[link]

Great Britain[link]

The existence of ethnic enclaves in the United Kingdom is controversial.

Southall Broadway, a predominantly Asian area in London, where less than 12 percent of the population is white, has been cited as an example of a 'ghetto', but in reality the area is home to a number of different ethnic groups and religious groups.^[29][30] Analysis of data from Census 2001 revealed that only two wards in England and Wales, both in Birmingham, had one dominant non-white ethnic group comprising more than two-thirds of the local population, but there were 20 wards where whites were a minority making up less than a third of the local population.^[31][32] By 2001, two London boroughs - Newham and Brent - had 'minority majority' populations, and most parts of the city tend to have a diverse population.

A "peace line" in Belfast, seen from the Irish nationalist/republican side. The small back gardens of houses are protected by cages as missiles are sometimes thrown from the other side

Mural at the edge of a loyalist ghetto in Belfast

The Savile Town area of Dewsbury was described as "some 97-100% Asian Muslim" by Kirklees NHS in 2007.^[33] In the 2001 census, the area was 9.7% White British.^[34]

Northern Ireland[link]

In Northern Ireland, towns and cities have long been segregated along ethnic, religious and political lines. Northern Ireland's two main communities are its Irish nationalist/republican community (who mainly self-identify as Irish and/or Catholic) and its unionist/loyalist community (who mainly self-identify as British and/or Protestant). Ghettos emerged in Belfast during the riots that accompanied the Irish War of Independence. For safety, people fled to areas where their community was the majority. They then sealed-off these neighborhoods with barricades to keep-out rioters or gunmen from the other side. Many more ghettos emerged after the 1969 riots and beginning of the "Troubles". In August 1969 the British Army was deployed to restore order and separate the two sides. The government built separation barriers called "peace lines". Many of the ghettos came under the control of paramilitaries such as the (republican) Provisional Irish Republican Army and the (loyalist) Ulster Defence Association. One of the most notable ghettos was Free Derry.

See also[link]

References[link]

How radio communication works. Information such as sound is transformed into an electronic signal which is applied to a transmitter. The transmitter sends the information through space on a radio wave (electromagnetic wave). A receiver intercepts some of the radio wave and extracts the information-bearing electronic signal, which is converted back to its original form by a transducer such as a speaker.

Radio is the transmission of signals through free space by electromagnetic waves with frequencies significantly below visible light, in the radio frequency range, from about 3 kHz to 300 GHz.^[1] These waves are called radio waves. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space.

Information, such as sound, is carried by systematically changing (modulating) some property of the radiated waves, such as their amplitude, frequency, phase, or pulse width. When radio waves strike an electrical conductor, the oscillating fields induce an alternating current in the conductor. The information in the waves can be extracted and transformed back into its original form.

Classic radio receiver dial

Etymology[link]

The etymology of "radio" or "radiotelegraphy" reveals that it was called "wireless telegraphy," which was shortened to "wireless" in Britain. The prefix radio- in the sense of wireless transmission, was first recorded in the word radioconductor, a description provided by the French physicist Édouard Branly in 1897. It is based on the verb to radiate (in Latin "radius" means "spoke of a wheel, beam of light, ray").

The word "radio" also appears in a 1907 article by Lee De Forest. It was adopted by the United States Navy in 1912, to distinguish radio from several other "wireless" communication technologies in use at the time, such as the photophone. The term became common by the time of the first commercial broadcasts in the United States in the 1920s. (The noun "broadcasting" itself came from an agricultural term, meaning "scattering seeds widely.") The term was adopted by other languages in Europe and Asia. British Commonwealth countries continued to commonly use the term "wireless" until the mid-20th century, though the magazine of the BBC in the UK has been called Radio Times ever since it was first published in the early 1920s.

In recent years the term "wireless" has gained renewed popularity through the rapid growth of short-range computer networking, e.g., Wireless Local Area Network (WLAN), Wi-Fi, and Bluetooth, as well as mobile telephony, e.g., GSM and UMTS. Today, the term "radio" often refers to the actual transceiver device or chip, whereas "wireless" refers to the system and/or method used for radio communication; hence one talks about radio transceivers and Radio Frequency Identification (RFID), but about wireless devices and wireless sensor networks.

Processes[link]

Radio systems used for communications will have the following elements. With more than 100 years of development, each process is implemented by a wide range of methods, specialized for different communications purposes.

Transmitter and modulation[link]

Each system contains a transmitter. This consists of a source of electrical energy, producing alternating current of a desired frequency of oscillation. The transmitter contains a system to modulate (change) some property of the energy produced to impress a signal on it. This modulation might be as simple as turning the energy on and off, or altering more subtle properties such as amplitude, frequency, phase, or combinations of these properties. The transmitter sends the modulated electrical energy to a tuned resonant antenna; this structure converts the rapidly changing alternating current into an electromagnetic wave that can move through free space (sometimes with a particular polarization).

An audio signal (top) may be carried by an AM or FM radio wave.

Amplitude modulation of a carrier wave works by varying the strength of the transmitted signal in proportion to the information being sent. For example, changes in the signal strength can be used to reflect the sounds to be reproduced by a speaker, or to specify the light intensity of television pixels. It was the method used for the first audio radio transmissions, and remains in use today. "AM" is often used to refer to the mediumwave broadcast band (see AM radio).

Frequency modulation varies the frequency of the carrier. The instantaneous frequency of the carrier is directly proportional to the instantaneous value of the input signal. Digital data can be sent by shifting the carrier's frequency among a set of discrete values, a technique known as frequency-shift keying.

FM is commonly used at VHF radio frequencies for high-fidelity broadcasts of music and speech (see FM broadcasting). Normal (analog) TV sound is also broadcast using FM.

Angle modulation alters the instantaneous phase of a carrier wave to transmit a signal. It is another term for Phase modulation.

Antennas and propagation[link]

Electromagnetic waves travel through space either directly, or have their path altered by reflection, refraction or diffraction. The intensity of the waves diminishes due to geometric dispersion (the inverse-square law); some energy may also be absorbed by the intervening medium in some cases. Noise will generally alter the desired signal; this electromagnetic interference comes from natural sources, as well as from artificial sources such as other transmitters and accidental radiators. Noise is also produced at every step due to the inherent properties of the devices used. If the magnitude of the noise is large enough, the desired signal will no longer be discernible; this is the fundamental limit to the range of radio communications.

Resonance[link]

Electrical resonance of tuned circuits in radios allow individual stations to be selected. A resonant circuit will respond strongly to a particular frequency, and much less so to differing frequencies. This allows the radio receiver to discriminate between multiple signals differing in frequency.

Receiver and demodulation[link]

A Crystal Receiver, consisting of an antenna, rheostat, coil, crystal rectifier, capacitor, headphones and ground connection.

The electromagnetic wave is intercepted by a tuned receiving antenna; this structure captures some of the energy of the wave and returns it to the form of oscillating electrical currents. At the receiver, these currents are demodulated, which is conversion to a usable signal form by a detector sub-system. The receiver is "tuned" to respond preferentially to the desired signals, and reject undesired signals.

Early radio systems relied entirely on the energy collected by an antenna to produce signals for the operator. Radio became more useful after the invention of electronic devices such as the vacuum tube and later the transistor, which made it possible to amplify weak signals. Today radio systems are used for applications from walkie-talkie children's toys to the control of space vehicles, as well as for broadcasting, and many other applications.

A radio receiver receives its input from an antenna, uses electronic filters to separate a wanted radio signal from all other signals picked up by this antenna, amplifies it to a level suitable for further processing, and finally converts through demodulation and decoding the signal into a form usable for the consumer, such as sound, pictures, digital data, measurement values, navigational positions, etc.^[2]

Radio band[link]

Radio frequencies occupy the range from a few hertz to 300 GHz, although commercially important uses of radio use only a small part of this spectrum.^[3] Other types of electromagnetic radiation, with frequencies above the RF range, are microwave, infrared, visible light, ultraviolet, X-rays and gamma rays. Since the energy of an individual photon of radio frequency is too low to remove an electron from an atom, radio waves are classified as non-ionizing radiation.

Communication systems[link]

A radio communication system sends signals by radio.^[4] Types of radio communication systems deployed depend on technology, standards, regulations, radio spectrum allocation, user requirements, service positioning, and investment.^[5]

The radio equipment involved in communication systems includes a transmitter and a receiver, each having an antenna and appropriate terminal equipment such as a microphone at the transmitter and a loudspeaker at the receiver in the case of a voice-communication system.^[6]

The power consumed in a transmitting station varies depending on the distance of communication and the transmission conditions. The power received at the receiving station is usually only a tiny fraction of the transmitter's output, since communication depends on receiving the information, not the energy, that was transmitted.

Classical radio communications systems use frequency-division multiplexing (FDM) as a strategy to split up and share the available radio-frequency bandwidth for use by different parties communications concurrently. Modern radio communication systems include those that divide up a radio-frequency band by time-division multiplexing (TDM) and code-division multiplexing (CDM) as alternatives to the classical FDM strategy. These systems offer different tradeoffs in supporting multiple users, beyond the FDM strategy that was ideal for broadcast radio but less so for applications such as mobile telephony.

A radio communication system may send information only one way. For example, in broadcasting a single transmitter sends signals to many receivers. Two stations may take turns sending and receiving, using a single radio frequency; this is called "simplex." By using two radio frequencies, two stations may continuously and concurrently send and receive signals - this is called "duplex" operation.

History[link]

19th century[link]

The meaning and usage of the word "radio" has developed in parallel with developments within the field of communications and can be seen to have three distinct phases: electromagnetic waves and experimentation; wireless communication and technical development; and radio broadcasting and commercialization. Many individuals—inventors, engineers, developers, businessmen - contributed to produce the modern idea of radio and thus the origins and 'invention' are multiple and controversial. Early radio designs could not transmit sound or speech and were called the "wireless telegraph."

Development from a laboratory demonstration to a commercial entity spanned several decades and required the efforts of many practitioners. In 1878, David E. Hughes noticed that sparks could be heard in a telephone receiver when experimenting with his carbon microphone. He developed this carbon-based detector further and eventually could detect signals over a few hundred yards. He demonstrated his discovery to the Royal Society in 1880, but was told it was merely induction, and therefore abandoned further research.

Experiments were undertaken by Thomas Edison and his employees of Menlo Park. Edison applied in 1885 to the U.S. Patent Office for a patent on an electrostatic coupling system between elevated terminals. The patent was granted as U.S. Patent 465,971 on December 29, 1891. The Marconi Company would later purchase rights to the Edison patent to protect them legally from lawsuits.^[7]

Tesla demonstrating wireless transmissions during his high frequency and potential lecture of 1891. After continued research, Tesla presented the fundamentals of radio in 1893.

In 1893, in St. Louis, Missouri, Nikola Tesla made devices for his experiments with electricity. Addressing the Franklin Institute in Philadelphia and the National Electric Light Association, he described and demonstrated the principles of his wireless work.^[8] The descriptions contained all the elements that were later incorporated into radio systems before the development of the vacuum tube. He initially experimented with magnetic receivers, unlike the coherers (detecting devices consisting of tubes filled with iron filings which had been invented by Temistocle Calzecchi-Onesti at Fermo in Italy in 1884) used by Guglielmo Marconi and other early experimenters.^[9]

A demonstration of wireless telegraphy took place in the lecture theater of the Oxford University Museum of Natural History on August 14, 1894, carried out by Professor Oliver Lodge and Alexander Muirhead. During the demonstration a radio signal was sent from the neighboring Clarendon laboratory building, and received by apparatus in the lecture theater.

In 1895 Alexander Stepanovich Popov built his first radio receiver, which contained a coherer. Further refined as a lightning detector, it was presented to the Russian Physical and Chemical Society on May 7, 1895. A depiction of Popov's lightning detector was printed in the Journal of the Russian Physical and Chemical Society the same year. Until recently, mistakenly believed that it was the first description (publication of the minutes 15/201 of this session — December issue of the journal RPCS^[10]), but in fact the first description of the device gave Dmitry Aleksandrovich Lachinov in July 1895 in the 2nd edition of his course "Fundamentals of Meteorology and climatology" — the first in Russia.^[11][12] Popov's receiver was created on the improved basis of Lodge's receiver, and originally intended for reproduction of its experiments.

In 1895, Marconi built a wireless system capable of transmitting signals at long distances (1.5 mi./ 2.4 km).^[13][14] In radio transmission technology, early public experimenters had made short distance broadcasts.^[15] Marconi achieved long range signalling due to a wireless transmitting apparatus and a radio receiver claimed by him.^[16][17] From Marconi's experiments, the phenomenon that transmission range is proportional to the square of antenna height is known as "Marconi's law."^[18]

Marconi's experimental apparatus proved to be a complete, commercially successful radio transmission system.^[17][19][20] According to the Proceedings of the United States Naval Institute in 1899, the Marconi instruments had a "[...] coherer, principle of which was discovered some twenty years ago, [and was] the only electrical instrument or device contained in the apparatus that is at all new."^[21]

Telephone Herald in Budapest, Hungary (1901).

In 1896, Marconi was awarded British patent 12039, Improvements in transmitting electrical impulses and signals and in apparatus there-for, for radio. In 1897, he established a radio station on the Isle of Wight, England. Marconi opened his "wireless" factory in Hall Street, Chelmsford, England in 1898, employing around 60 people. Shortly after the 1900s, Marconi held the patent rights for radio.

20th century[link]

In 1900, Brazilian priest Roberto Landell de Moura transmitted the human voice by wireless. According the newspaper Jornal do Comercio (June 10, 1900), he conducted his first public experiment on June 3, 1900, in front of journalists and the General Consul of Great Britain, C.P. Lupton, in São Paulo, Brazil, for a distance of approximately 8 km. The points of transmission and reception were Alto de Santana and Paulista Avenue.^[22]

One year after that experiment, he received his first patent from the Brazilian government. It was described as "equipment for the purpose of phonetic transmissions through space, land and water elements at a distance with or without the use of wires." Four months later, knowing that his invention had real value, he left Brazil for the United States of America with the intent of patenting the machine at the US Patent Office in Washington, DC.

Having few resources, he had to rely on friends to push his project. In spite of great difficulty, three patents were awarded: "The Wave Transmitter" (October 11, 1904) which is the precursor of today's radio transceiver; "The Wireless Telephone" and the "Wireless Telegraph," both dated November 22, 1904.

"The Wireless Telephone" U S Patent Office in Washington, DC

The next advancement was the vacuum tube detector, invented by Westinghouse engineers. On Christmas Eve 1906, Reginald Fessenden used a synchronous rotary-spark transmitter for the first radio program broadcast, from Ocean Bluff-Brant Rock, Massachusetts. Ships at sea heard a broadcast that included Fessenden playing O Holy Night on the violin and reading a passage from the Bible.^[23]

This was, for all intents and purposes, the first transmission of what is now known as amplitude modulation or AM radio. The first radio news program was broadcast August 31, 1920 by station 8MK in Detroit, Michigan, which survives today as all-news format station WWJ under ownership of the CBS network. The first college radio station began broadcasting on October 14, 1920 from Union College, Schenectady, New York under the personal call letters of Wendell King, an African-American student at the school.^[23]

That month 2ADD (renamed WRUC in 1947), aired what is believed to be the first public entertainment broadcast in the United States, a series of Thursday night concerts initially heard within a 100-mile (160 km) radius and later for a 1,000-mile (1,600 km) radius. In November 1920, it aired the first broadcast of a sporting event.^[23][24] At 9 pm on August 27, 1920, Sociedad Radio Argentina aired a live performance of Richard Wagner's opera Parsifal from the Coliseo Theater in downtown Buenos Aires. Only about twenty homes in the city had receivers to tune in this radio program. Meanwhile, regular entertainment broadcasts commenced in 1922 from the Marconi Research Centre at Writtle, England.

Sports broadcasting began at this time as well, including the college football on radio broadcast of a 1921 West Virginia vs. Pittsburgh football game.^[25]

In 1943, the United States Supreme Court invalidated one of the Marconi patents, number 763,772 (1904), on the basis it had been anticipated by Tesla, Lodge, and others. After years of patent battles by Marconi's company, the United States Supreme Court, in the 1943 case of Marconi Wireless Telegraph co. of America v. United States, 320 U.S. 1 (1943), said that "it is now held that in the important advance upon his basic patent Marconi did nothing that had not already been seen and disclosed."^[26][27][28]

Although Marconi claimed that he had no knowledge of prior art from Tesla's patents, the Supreme Court considered his claim false.^[29] In addition to that ruling from the Supreme Court, the United States Court of Claims invalidated the fundamental 1935 Marconi patent.^[30] This case defined radio by the statement: "A radio communication system requires two tuned circuits each at the transmitter and receiver, all four tuned to the same frequency."^[31] The court determined that Tesla's patent clearly was the first to disclose a system which could be used for wireless communication of intelligible messages (such as human voice and music) and used the four-circuit tuned combination.^[32]

An American girl listens to a radio during the Great Depression.

In contrast, related developments in the United Kingdom saw the High Court of Justice uphold Marconi's British Patent, issued on April 26, 1900. This patent disclosed a four-circuit system, which was strikingly similar to a four-circuit system disclosed in U.S. patent #645,576 that was issued earlier to Tesla on March 20, 1900. On the matter of invention, it is held that Marconi knowingly and unknowingly used the scientific and experimental work of others who were devising their own radio tuning apparatus' around the same time, such as the work of American electrical engineer John Stone Stone who was issued several U.S. patents between 1904 and 1908. However, what made Marconi more successful than any other was his ability to commercialize radio and its associated equipment into a global business.^{[33][dubious – discuss]}

One of the first developments in the early 20th century was that aircraft used commercial AM radio stations for navigation. This continued until the early 1960s when VOR systems became widespread.^[34] In the early 1930s, single sideband and frequency modulation were invented by amateur radio operators. By the end of the decade, they were established commercial modes. Radio was used to transmit pictures visible as television as early as the 1920s. Commercial television transmissions started in North America and Europe in the 1940s.

The Regency TR-1 which used Texas Instruments' NPN transistors was the world's first commercially produced transistor radio.

In 1954, the Regency company introduced a pocket transistor radio, the TR-1, powered by a "standard 22.5 V Battery." In 1955, the newly formed Sony company introduced its first transistorized radio.^[35] It was small enough to fit in a vest pocket, powered by a small battery. It was durable, because it had no vacuum tubes to burn out. Over the next 20 years, transistors replaced tubes almost completely except for high-power transmitters.

By 1963, color television was being broadcast commercially (though not all broadcasts or programs were in color), and the first (radio) communication satellite, Telstar, was launched. In the late 1960s, the U.S. long-distance telephone network began to convert to a digital network, employing digital radios for many of its links. In the 1970s, LORAN became the premier radio navigation system.

Soon, the U.S. Navy experimented with satellite navigation, culminating in the launch of the Global Positioning System (GPS) constellation in 1987. In the early 1990s, amateur radio experimenters began to use personal computers with audio cards to process radio signals. In 1994, the U.S. Army and DARPA launched an aggressive, successful project to construct a software-defined radio that can be programmed to be virtually any radio by changing its software program. Digital transmissions began to be applied to broadcasting in the late 1990s. 2012 saw the first transmission of the Passover classic "Matzah" on Harvard's WHRB station.

Uses of radio[link]

Early uses were maritime, for sending telegraphic messages using Morse code between ships and land. The earliest users included the Japanese Navy scouting the Russian fleet during the Battle of Tsushima in 1905. One of the most memorable uses of marine telegraphy was during the sinking of the RMS Titanic in 1912, including communications between operators on the sinking ship and nearby vessels, and communications to shore stations listing the survivors.

Radio was used to pass on orders and communications between armies and navies on both sides in World War I; Germany used radio communications for diplomatic messages once it discovered that its submarine cables had been tapped by the British. The United States passed on President Woodrow Wilson's Fourteen Points to Germany via radio during the war. Broadcasting began from San Jose, California in 1909,^[36] and became feasible in the 1920s, with the widespread introduction of radio receivers, particularly in Europe and the United States. Besides broadcasting, point-to-point broadcasting, including telephone messages and relays of radio programs, became widespread in the 1920s and 1930s. Another use of radio in the pre-war years was the development of detection and locating of aircraft and ships by the use of radar (RAdio Detection And Ranging).

Today, radio takes many forms, including wireless networks and mobile communications of all types, as well as radio broadcasting. Before the advent of television, commercial radio broadcasts included not only news and music, but dramas, comedies, variety shows, and many other forms of entertainment (the era from the late 1920s to the mid-1950s is commonly called radio's "Golden Age"). Radio was unique among methods of dramatic presentation in that it used only sound. For more, see radio programming.

Audio[link]

A Fisher 500 AM/FM hi-fi receiver from 1959.

AM radio uses amplitude modulation, in which the amplitude of the transmitted signal is made proportional to the sound amplitude captured (transduced) by the microphone, while the transmitted frequency remains unchanged. Transmissions are affected by static and interference because lightning and other sources of radio emissions on the same frequency add their amplitudes to the original transmitted amplitude.

In the early part of the 20th century, American AM radio stations broadcast with powers as high as 500 kW, and some could be heard worldwide; these stations' transmitters were commandeered for military use by the US Government during World War II. Currently, the maximum broadcast power for a civilian AM radio station in the United States and Canada is 50 kW, and the majority of stations that emit signals this powerful were grandfathered in (see List of 50 kW AM radio stations in the United States). In 1986 KTNN received the last granted 50,000 watt license. These 50 kW stations are generally called "clear channel" stations (not to be confused with Clear Channel Communications), because within North America each of these stations has exclusive use of its broadcast frequency throughout part or all of the broadcast day.

Bush House, home of the BBC World Service.

FM broadcast radio sends music and voice with higher fidelity than AM radio. In frequency modulation, amplitude variation at the microphone causes the transmitter frequency to fluctuate. Because the audio signal modulates the frequency and not the amplitude, an FM signal is not subject to static and interference in the same way as AM signals. Due to its need for a wider bandwidth, FM is transmitted in the Very High Frequency (VHF, 30 MHz to 300 MHz) radio spectrum.

VHF radio waves act more like light, traveling in straight lines; hence the reception range is generally limited to about 50–200 miles. During unusual upper atmospheric conditions, FM signals are occasionally reflected back towards the Earth by the ionosphere, resulting in long distance FM reception. FM receivers are subject to the capture effect, which causes the radio to only receive the strongest signal when multiple signals appear on the same frequency. FM receivers are relatively immune to lightning and spark interference.

High power is useful in penetrating buildings, diffracting around hills, and refracting in the dense atmosphere near the horizon for some distance beyond the horizon. Consequently, 100,000 watt FM stations can regularly be heard up to 100 miles (160 km) away, and farther (e.g., 150 miles, 240 km) if there are no competing signals.

A few old, "grandfathered" stations do not conform to these power rules. WBCT-FM (93.7) in Grand Rapids, Michigan, US, runs 320,000 watts ERP, and can increase to 500,000 watts ERP by the terms of its original license. Such a huge power level does not usually help to increase range as much as one might expect, because VHF frequencies travel in nearly straight lines over the horizon and off into space. Nevertheless, when there were fewer FM stations competing, this station could be heard near Bloomington, Illinois, US, almost 300 miles (500 km) away.^{[citation needed]}

FM subcarrier services are secondary signals transmitted in a "piggyback" fashion along with the main program. Special receivers are required to utilize these services. Analog channels may contain alternative programming, such as reading services for the blind, background music or stereo sound signals. In some extremely crowded metropolitan areas, the sub-channel program might be an alternate foreign-language radio program for various ethnic groups. Sub-carriers can also transmit digital data, such as station identification, the current song's name, web addresses, or stock quotes. In some countries, FM radios automatically re-tune themselves to the same channel in a different district by using sub-bands.

Aviation voice radios use VHF AM. AM is used so that multiple stations on the same channel can be received. (Use of FM would result in stronger stations blocking out reception of weaker stations due to FM's capture effect). Aircraft fly high enough that their transmitters can be received hundreds of miles (or kilometres) away, even though they are using VHF.

Degen DE1103, an advanced world mini-receiver with single sideband modulation and dual conversion

Marine voice radios can use single sideband voice (SSB) in the shortwave High Frequency (HF—3 MHz to 30 MHz) radio spectrum for very long ranges or narrowband FM in the VHF spectrum for much shorter ranges. Narrowband FM sacrifices fidelity to make more channels available within the radio spectrum, by using a smaller range of radio frequencies, usually with five kHz of deviation, versus the 75 kHz used by commercial FM broadcasts, and 25 kHz used for TV sound.

Government, police, fire and commercial voice services also use narrowband FM on special frequencies. Early police radios used AM receivers to receive one-way dispatches.

Civil and military HF (high frequency) voice services use shortwave radio to contact ships at sea, aircraft and isolated settlements. Most use single sideband voice (SSB), which uses less bandwidth than AM. On an AM radio SSB sounds like ducks quacking, or the adults in a Charlie Brown cartoon. Viewed as a graph of frequency versus power, an AM signal shows power where the frequencies of the voice add and subtract with the main radio frequency. SSB cuts the bandwidth in half by suppressing the carrier and one of the sidebands. This also makes the transmitter about three times more powerful, because it doesn't need to transmit the unused carrier and sideband.

TETRA, Terrestrial Trunked Radio is a digital cell phone system for military, police and ambulances. Commercial services such as XM, WorldSpace and Sirius offer encrypted digital Satellite radio.

Telephony[link]

Mobile phones transmit to a local cell site (transmitter/receiver) that ultimately connects to the public switched telephone network (PSTN) through an optic fiber or microwave radio and other network elements. When the mobile phone nears the edge of the cell site's radio coverage area, the central computer switches the phone to a new cell. Cell phones originally used FM, but now most use various digital modulation schemes. Recent developments in Sweden (such as DROPme) allow for the instant downloading of digital material from a radio broadcast (such as a song) to a mobile phone.

Satellite phones use satellites rather than cell towers to communicate.

Video[link]

Television sends the picture as AM and the sound as AM or FM, with the sound carrier a fixed frequency (4.5 MHz in the NTSC system) away from the video carrier. Analog television also uses a vestigial sideband on the video carrier to reduce the bandwidth required.

Digital television uses 8VSB modulation in North America (under the ATSC digital television standard), and COFDM modulation elsewhere in the world (using the DVB-T standard). A Reed–Solomon error correction code adds redundant correction codes and allows reliable reception during moderate data loss. Although many current and future codecs can be sent in the MPEG transport stream container format, as of 2006 most systems use a standard-definition format almost identical to DVD: MPEG-2 video in Anamorphic widescreen and MPEG layer 2 (MP2) audio. High-definition television is possible simply by using a higher-resolution picture, but H.264/AVC is being considered as a replacement video codec in some regions for its improved compression. With the compression and improved modulation involved, a single "channel" can contain a high-definition program and several standard-definition programs.

Navigation[link]

All satellite navigation systems use satellites with precision clocks. The satellite transmits its position, and the time of the transmission. The receiver listens to four satellites, and can figure its position as being on a line that is tangent to a spherical shell around each satellite, determined by the time-of-flight of the radio signals from the satellite. A computer in the receiver does the math.

Radio direction-finding is the oldest form of radio navigation. Before 1960 navigators used movable loop antennas to locate commercial AM stations near cities. In some cases they used marine radiolocation beacons, which share a range of frequencies just above AM radio with amateur radio operators. LORAN systems also used time-of-flight radio signals, but from radio stations on the ground.

VOR (Very High Frequency Omnidirectional Range), systems (used by aircraft), have an antenna array that transmits two signals simultaneously. A directional signal rotates like a lighthouse at a fixed rate. When the directional signal is facing north, an omnidirectional signal pulses. By measuring the difference in phase of these two signals, an aircraft can determine its bearing or radial from the station, thus establishing a line of position. An aircraft can get readings from two VORs and locate its position at the intersection of the two radials, known as a "fix."

When the VOR station is collocated with DME (Distance Measuring Equipment), the aircraft can determine its bearing and range from the station, thus providing a fix from only one ground station. Such stations are called VOR/DMEs. The military operates a similar system of navaids, called TACANs, which are often built into VOR stations. Such stations are called VORTACs. Because TACANs include distance measuring equipment, VOR/DME and VORTAC stations are identical in navigation potential to civil aircraft.

Radar[link]

Radar (Radio Detection And Ranging) detects objects at a distance by bouncing radio waves off them. The delay caused by the echo measures the distance. The direction of the beam determines the direction of the reflection. The polarization and frequency of the return can sense the type of surface. Navigational radars scan a wide area two to four times per minute. They use very short waves that reflect from earth and stone. They are common on commercial ships and long-distance commercial aircraft.

General purpose radars generally use navigational radar frequencies, but modulate and polarize the pulse so the receiver can determine the type of surface of the reflector. The best general-purpose radars distinguish the rain of heavy storms, as well as land and vehicles. Some can superimpose sonar data and map data from GPS position.

Search radars scan a wide area with pulses of short radio waves. They usually scan the area two to four times a minute. Sometimes search radars use the Doppler effect to separate moving vehicles from clutter. Targeting radars use the same principle as search radar but scan a much smaller area far more often, usually several times a second or more. Weather radars resemble search radars, but use radio waves with circular polarization and a wavelength to reflect from water droplets. Some weather radar use the Doppler effect to measure wind speeds.

Data (digital radio)[link]

2008 Pure One Classic digital radio

Most new radio systems are digital, see also: Digital TV, Satellite Radio, Digital Audio Broadcasting. The oldest form of digital broadcast was spark gap telegraphy, used by pioneers such as Marconi. By pressing the key, the operator could send messages in Morse code by energizing a rotating commutating spark gap. The rotating commutator produced a tone in the receiver, where a simple spark gap would produce a hiss, indistinguishable from static. Spark-gap transmitters are now illegal, because their transmissions span several hundred megahertz. This is very wasteful of both radio frequencies and power.

The next advance was continuous wave telegraphy, or CW (Continuous Wave), in which a pure radio frequency, produced by a vacuum tube electronic oscillator was switched on and off by a key. A receiver with a local oscillator would "heterodyne" with the pure radio frequency, creating a whistle-like audio tone. CW uses less than 100 Hz of bandwidth. CW is still used, these days primarily by amateur radio operators (hams). Strictly, on-off keying of a carrier should be known as "Interrupted Continuous Wave" or ICW or on-off keying (OOK).

Radioteletype equipment usually operates on short-wave (HF) and is much loved by the military because they create written information without a skilled operator. They send a bit as one of two tones using frequency-shift keying. Groups of five or seven bits become a character printed by a teleprinter. From about 1925 to 1975, radioteletype was how most commercial messages were sent to less developed countries. These are still used by the military and weather services.

Aircraft use a 1200 Baud radioteletype service over VHF to send their ID, altitude and position, and get gate and connecting-flight data. Microwave dishes on satellites, telephone exchanges and TV stations usually use quadrature amplitude modulation (QAM). QAM sends data by changing both the phase and the amplitude of the radio signal. Engineers like QAM because it packs the most bits into a radio signal when given an exclusive (non-shared) fixed narrowband frequency range. Usually the bits are sent in "frames" that repeat. A special bit pattern is used to locate the beginning of a frame.

Modern GPS receivers.

Communication systems that limit themselves to a fixed narrowband frequency range are vulnerable to jamming. A variety of jamming-resistant spread spectrum techniques were initially developed for military use, most famously for Global Positioning System satellite transmissions. Commercial use of spread spectrum began in the 1980s. Bluetooth, most cell phones, and the 802.11b version of Wi-Fi each use various forms of spread spectrum.

Systems that need reliability, or that share their frequency with other services, may use "coded orthogonal frequency-division multiplexing" or COFDM. COFDM breaks a digital signal into as many as several hundred slower subchannels. The digital signal is often sent as QAM on the subchannels. Modern COFDM systems use a small computer to make and decode the signal with digital signal processing, which is more flexible and far less expensive than older systems that implemented separate electronic channels.

COFDM resists fading and ghosting because the narrow-channel QAM signals can be sent slowly. An adaptive system, or one that sends error-correction codes can also resist interference, because most interference can affect only a few of the QAM channels. COFDM is used for Wi-Fi, some cell phones, Digital Radio Mondiale, Eureka 147, and many other local area network, digital TV and radio standards.

Heating[link]

Radio-frequency energy generated for heating of objects is generally not intended to radiate outside of the generating equipment, to prevent interference with other radio signals. Microwave ovens use intense radio waves to heat food. Diathermy equipment is used in surgery for sealing of blood vessels. Induction furnaces are used for melting metal for casting, and induction hobs for cooking.

Amateur radio service[link]

Amateur radio station with multiple receivers and transceivers

Amateur radio, also known as "ham radio," is a hobby in which enthusiasts are licensed to communicate on a number of bands in the radio frequency spectrum non-commercially and for their own enjoyment. They may also provide emergency and public service assistance. This has been very beneficial in emergencies, saving lives in many instances.^[37]

Radio amateurs use a variety of modes, including nostalgic ones like Morse code and experimental ones like Low-Frequency Experimental Radio. Several forms of radio were pioneered by radio amateurs and later became commercially important, including FM, single-sideband (SSB), AM, digital packet radio and satellite repeaters. Some amateur frequencies may be disrupted illegally by power-line internet service.

Unlicensed radio services[link]

Unlicensed, government-authorized personal radio services such as Citizens' band radio in Australia, the US, and Europe, and Family Radio Service and Multi-Use Radio Service in North America exist to provide simple, (usually) short range communication for individuals and small groups, without the overhead of licensing. Similar services exist in other parts of the world. These radio services involve the use of handheld units.

Free radio stations, sometimes called pirate radio or "clandestine" stations, are unauthorized, unlicensed, illegal broadcasting stations. These are often low power transmitters operated on sporadic schedules by hobbyists, community activists, or political and cultural dissidents. Some pirate stations operating offshore in parts of Europe and the United Kingdom more closely resembled legal stations, maintaining regular schedules, using high power, and selling commercial advertising time.^[38][39]

Radio control (RC)[link]

Radio remote controls use radio waves to transmit control data to a remote object as in some early forms of guided missile, some early TV remotes and a range of model boats, cars and airplanes. Large industrial remote-controlled equipment such as cranes and switching locomotives now usually use digital radio techniques to ensure safety and reliability.

In Madison Square Garden, at the Electrical Exhibition of 1898, Nikola Tesla successfully demonstrated a radio-controlled boat.^[40] He was awarded U.S. patent No. 613,809 for a "Method of and Apparatus for Controlling Mechanism of Moving Vessels or Vehicles."^[41]

See also[link]

Radio portal

References[link]

General information

• A História da Rádio em Datas (1819-1997) (in Portuguese) - notes on etymology
• L. de Forest, article in Electrical World 22 June 1270/1 (1907), early use of word "radio."
• http://web.mit.edu/varun_ag/www/bose.html - It contains a proof that Sir Jagadish Chandra Bose invented the Mercury Coherer which was later used by Guglielmo Marconi and along with other patents.
• Cheney, Margaret (1981). Tesla - Man Out of Time. New York: Simon & Schuster. ISBN 978-0-7432-1536-7. 

Footnotes

Further reading[link]

• Sewall, C. H. (1904). Wireless telegraphy: its origins, development, inventions, and apparatus. New York: D. Van Nostrand.
• Mills, J. (1917). Radio communication, theory and methods, with an appendix on transmission over wires. New York: McGraw-Hill book company [etc., etc.].
• Lauer, H., & Brown, H. L. (1920). Radio engineering principles. New York: McGraw-Hill book company; [etc., etc.].
• Cockaday, L. M. (1922). Radio-telephony for everyone; the wireless: how to construct and maintain modern transmitting and receiving apparatus. New York: Frederick A. Stokes.
• Hausmann, E., Goldsmith, A. N., Hazeltine, L. A., Hogan, J. V. L., Morecroft, J. H., Canavaciol, F. E., et al. (1922). Radio phone receiving; a practical book for everybody. New York: D. Van Nostrand.
• Buga, N.; Falko A., Chistyakov N.I. (1990) Chistyakov N.I. ed. Radio Receiver Theory Translated from the Russian by Boris V. Kuznetsov Moscow: Mir Publishers ISBN 5-03-001321-0  First published in Russian as «Радиоприёмные устройства» 
• Da Silva, E. (2001). High frequency and microwave engineering. Oxford: Butterworth-Heinemann.
• Clint Smith, Curt Gervelis (2003). Wireless Network Performance Handbook. McGraw-Hill Professional. ISBN 0-07-140655-7. http://books.google.com/books?id=nZAVGBoPevUC&pg=PA25&lr=&as_brr=3&ei=F4-sSKuzO6XmtgO4393BBA&sig=ACfU3U0g0vtYCOzP0LCCzdRfr7bgKwvTNg#PPA24,M1. 
• Hugh G. J. Aitkin: The Continuous Wave: Technology and the American Radio, 1900-1932 (Princeton University Press, 1985).
• Asa Briggs: The History of Broadcasting in the United Kingdom (Oxford University Press, 1961).
• John Dunning: On the Air. The Encyclopedia of Old-Time Radio. New York; Oxford: Oxford University Press, 1998. ISBN 0-19-507678-8
• Henry Ewbank and Sherman P. Lawton: Broadcasting: Radio and Television (Harper & Brothers, 1952).
• Marc Fisher: Something In The Air: Radio, Rock, and the Revolution That Shaped A Generation (Random House, 2007).
• Leland I. Anderson (ed.), "John Stone Stone, Nikola Tesla's Priority in Radio and Continuous-Wave Radiofrequency Apparatus." The AWA Review, Vol. 1. 1986. 24 pages, illustrated.
• Tom Lewis: Empire of the Air: The Men Who Made Radio, 1st ed., New York : E. Burlingame Books, 1991. ISBN 0-06-018215-6. "Empire of the Air: The Men Who Made Radio" (1992) by Ken Burns was a PBS documentary based on the book.
• W. Rupert Maclaurin: Invention and Innovation in the Radio Industry (The Macmillan Company, 1949).
• William B. Ray: FCC: The Ups and Downs of Radio-TV Regulation (Iowa State University Press, 1990).
• Alexander Russo: Points on the Dial: Golden Age Radio Beyond the Networks (Duke University Press; 2010) 278 pages; discusses regional and local radio as forms that "complicate" the image of the medium as a national unifier from the 1920s to the 1950s.
• Scannell, Paddy, and Cardiff, David. A Social History of British Broadcasting, Volume One, 1922-1939 (Basil Blackwell, 1991).
• Schwoch James. The American Radio Industry and Its Latin American Activities, 1900-1939 (University of Illinois Press, 1990).
• Christopher H. Sterling with Michael C. Keith (ed.): Encyclopedia of Radio. New York; London: Fitzroy Dearborn, 2004 (three vols.)
• Llewellyn White: The American Radio (University of Chicago Press, 1947).
• Ulrich L. Rohde, Jerry Whitaker: Communications Receivers, Third Edition, McGraw Hill, New York, NY, 2001, ISBN 0-07-136121-9.

External links[link]

Wikimedia Commons has media related to: Radio

Look up radio in Wiktionary, the free dictionary.

General

• Radio at the Open Directory Project
• "It's Radi-O! Essay by Richard Rubin, The Atlantic Monthly, January 1998.

History

• U.S. Supreme Court, "Marconi Wireless Telegraph co. of America v. United States." 320 U.S. 1. Nos. 369, 373. Argued 9–12 April 1943. Decided 21 June 1943.
• "Who Invented Radio?" Buzzle.com Date unknown. retrieved 20 January 2011.
• Steven Schoenherr's History of Radio
• The Broadcast Archive - Radio History on the Web! Retrieved 20 January 2011.
• Canadian Communications Foundation - The History on Canadian Broadcasting - 1920 onward. Retrieved 20 January 2011.
• United States Early Radio History -1897 to 1927. Retrieved 20 January 2011.
• Historic Radios from Around the World at Kurrajong Radio Museum, Australia - a private collection. Retrieved 20 January 2011.

Antiques

• George H. Clark Radioana Collection, ca. 1880 - 1950 - Archives Center, National Museum of American History, Smithsonian Institution
• A gallery of Antiques from the 1920s to the 1960s

Technical

• Radio Frequency Chart National Telecommunications and Information Administration (NTIA).
• IAteacher: Interactive Explanation of Radio Receiver Construction
• How Stuff Works - Radio
• VOR Basic Information
• Dr. Phil's Receiver Designs Single-Triode and Single-Transistor Regenerative Radio Designs
• How to design a traditional radio by Natalian Zhai, Silicon Labs

DX

• The British DX Club
• World of Radio Glenn Hauser's internationally known DX radio show

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