Chicago Jazz Event: 2008

Radio

Radio is the transmission of signals, by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space. Information is carried by systematically changing (modulating) some property of the radiated waves, such as amplitude, frequency, or phase. When radio waves pass an electrical conductor, the oscillating fields induce an alternating current in the conductor. This can be detected and transformed into sound or other signals that carry information.

The meaning and usage of the word "radio" has developed in parallel with developments within the field and can be seen to have three distinct phases: electromagnetic waves and experimentation; wireless communication and technical development; and radio broadcasting and commercialization. Many, many individuals -- inventors, engineers, developers, businessmen -- contributed to produce the modern idea of radio and thus the origins and 'invention' are multiple and controversial.

James Clerk Maxwell, a Scottish scientist, developed the theoretical basis for explaining electromagnetism. He predicted that electric and magnetic fields can couple together to form electromagnetic waves. Heinrich Hertz, a German scientist, is credited with being the first to produce and detect such waves at radio frequencies, in 1888, using a sparkgap transmitter in the Ultra High Frequency range.

In 1893, Nikola Tesla, in America, first demonstrated the principles of wireless communications. Tesla would later ultimately hold the patent rights in the United States. Ignoring prior art, some have suggested that the U.S. Supreme Court was influenced in its decision by the fact that the Marconi Company was suing the United States Government for use of its patents in World War I at the time. Physicists and inventors such as John Stone Stone and Alexander Stepanovich Popov have cited Tesla as the originator of wireless communications. In August 1894, Oliver Lodge, an English physicist and writer, transmitted radio signals at a meeting of the British Association for the Advancement of Science at the University of Oxford. In 1895, Guglielmo Marconi, an Italian inventor, began experimenting with wireless and went on to develop the world's first commercial system of radio communication. In 1896, Marconi was granted the world's first wireless telegraphy patent by the British Patent Office. Marconi has been generally credited with the development of radio by most scholars and historians. In 1909, Marconi was jointly awarded the Nobel Prize for Physics with Karl Ferdinand Braun "in recognition of their contributions to the development of wireless telegraphy." In 1943 the U.S. Supreme Court overturned Marconi's wireless patents and granted patent ownership to Nikola Tesla.

Etymology

Originally, radio or radiotelegraphy was called "wireless telegraphy", which was shortened to "wireless". The prefix radio- in the sense of wireless transmission, was first recorded in the word radioconductor, coined by the French physicist Edouard Branly in 1897 and based on the verb to radiate (in Latin "radius" means "spoke of a wheel, beam of light, ray"). "Radio" as a noun is said to have been coined by advertising expert Waldo Warren (White 1944). The word appears in a 1907 article by Lee de Forest, was adopted by the United States Navy in 1912 and 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".) The term was then adopted by other languages in Europe and Asia, although British Commonwealth countries continued to use the term "wireless" until the mid-20th century.

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), WiFi 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.

Invention

Although the invention of radio was long attributed to Guglielmo Marconi, the identity of the original inventor of radio (at the time called wireless telegraphy) is contentious. Development from a laboratory demonstration to commercial utility spanned several decades and required the efforts of many practitioners. In 1943 Tesla was granted the patent for the invention of radio when the U.S. Supreme Court overturned many of Marconi's radio patents.

Other significant contributions include:

In 1887, David E. Hughes transmitted signals by radio using a clockwork-keyed Spark Transmitter, achieving a range of approximately 500 metres.

In 1888, Heinrich Hertz produced and measured the Ultra High Frequency range (via a sparkgap transmitter).

In 1891, Nikola Tesla began wireless research. He developed means to reliably produce radio frequencies, publicly demonstrated the principles of radio, and transmitted long-distance signals.
Between 1893 and 1894, Roberto Landell de Moura, a Brazilian priest and scientist, conducted experiments. He did not publicise his achievement (publicly broadcasting human voice) until 1900 but later obtained a Brazilian patent.

In 1894 in Kolkata (Calcutta), Sir Jagdish Chandra Bose (J. C. Bose) invented the mercury coherer, together with the telephone receiver.

Alexander Stepanovich Popov, in 1894, built his first radio receiver, which contained a coherer, although in actuality the coherer was first invented by Edouard Branly. Popov demonstrated the coherer, further refined as a lightning detector, to the Russian Physical and Chemical Society on May 7, 1895.

In 1894, Guglielmo Marconi read about Hertz's and Tesla's work on wireless telegraphy, and began his own experiments.

In August 1894, Oliver Lodge, an English physicist and writer, transmitted radio signals at a meeting of the British Association for the Advancement of Science at the University of Oxford.

Late 1896 to early 1897, Tesla received wireless signals transmitted from the Houston Street lab in New York City to West Point, "a distance of about 30 miles."

In March 1897 Marconi transmitted wireless telegraphy signals over a distance of two miles on Salisbury Plains, followed in May 1897 by a test over water between Lavernock and Flat Holm in the Bristol Channel, a distance of just over three miles. He then moved the receiving equipment to Brean Down Fort and extended the range to just under ten miles.

In December of 1901 Guglielmo Marconi received the first transatlantic radio communication over a distance of 2,000 miles (3,200 km) from Poldhu, UK, to St. Johns, Newfoundland. Marconi was celebrated worldwide for this achievement. Soon after the patent was given to Marconi. He later received the Nobel Prize.

In early 1900s Canadian engineer-inventor Reginald Fessenden and American engineer Lee de Forest invented amplitude-modulated (AM) radio, allowing an audio signal to be sent over the air.

In 1935 Edwin H. Armstrong invented frequency-modulated (FM) radio, so that an audio signal can avoid "static," that is, interference from electrical equipment and atmospherics.

In 1943, the U.S. Supreme Court acknowledged that Marconi's work wasn't original because he had used 17 of Tesla's patents to accomplish his broadcasts, and the patent ownership is given back to Nikola Tesla. However, Tesla died shortly before the decision was announced.

History

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 in detail the principles of his wireless work. 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.

The first radio couldn't transmit sound or speech and was called the "wireless telegraph." The first public 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. Popov's receiver was created on the improved basis of Lodge's receiver, and originally intended for reproduction of its experiments.

In 1896, Marconi was awarded the British patent 12039, Improvements in transmitting electrical impulses and signals and in apparatus there-for, for radio. In 1897 he established the world's first radio station on the Isle of Wight, England. Marconi opened the world's first "wireless" factory in Hall Street, Chelmsford, England in 1898, employing around 50 people.

The next great invention 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. The first radio news program was broadcast August 31, 1920 by station 8MK in Detroit, Michigan. 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. That month 2ADD, later renamed WRUC in 1940, 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. At 9 pm on August 27, 1920, Sociedad Radio Argentina aired a live performance of Richard Wagner's Parsifal opera from the Coliseo Theater in downtown Buenos Aires, only about twenty homes in the city had a receiver to tune in. Meanwhile, regular entertainment broadcasts commenced in 1922 from the Marconi Research Centre at Writtle, England.

One of the first developments in the early 20th century (1900-1959) was that aircraft used commercial AM radio stations for navigation. This continued until the early 1960s when VOR systems finally became widespread (though AM stations are still marked on U.S. aviation charts). 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. In 1954, Regency introduced a pocket transistor radio, the TR-1, powered by a "standard 22.5 V Battery".

In 1960, Sony introduced its first transistorized radio, small enough to fit in a vest pocket, and able to be powered by a small battery. It was durable, because there were no tubes to burn out.

Over the next 20 years, transistors replaced tubes almost completely except for very high-power uses. By 1963 color television was being regularly transmitted commercially, 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 invention and launch of the 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.

Uses of radio

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 in 1909, 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. Radio was unique among methods of dramatic presentation in that it used only sound. For more, see radio programming.

Audio

AM broadcast radio sends music and voice in the Medium Frequency (MF—0.300 MHz to 3 MHz) radio spectrum. 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 that are transmitting at the same frequency add their amplitudes to the original transmitted amplitude. The most wattage an AM radio station in the United States and Canada is allowed to use is 50,000 watts and the majority of stations that emit signals this powerful were grandfathered in; these include WGN (AM), WJR, KGA and CKLW. In 1986 KTNN received the last granted 50,000 watt license.

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 50-100 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 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, USA, 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, USA, almost 300 miles (500 km) away.

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.

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. 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 (usually) lower sideband. 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

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. They come in two types: INMARSAT and Iridium. Both types provide world-wide coverage. INMARSAT uses geosynchronous satellites, with aimed high-gain antennas on the vehicles. Iridium uses 66 Low Earth Orbit satellites as the cells.

Video

Television sends the picture as AM and the sound as 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-2 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

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

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)

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).

Radio teletypes usually operate on short-wave (HF) and are much loved by the military because they create written information without a skilled operator. They send a bit as one of two tones. Groups of five or seven bits become a character printed by a teletype. From about 1925 to 1975, radio teletype 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.

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 begin 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 WiFi, some cell phones, Digital Radio Mondiale, Eureka 147, and many other local area network, digital TV and radio standards.

Heating

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.

Amateur radio service

Amateur radio is a hobby in which enthusiasts purchase or build their own equipment and use radio for their own enjoyment. They may also provide an emergency and public-service radio service. This has been of great use, saving lives in many instances. Radio amateurs are licensed to use frequencies in a large number of narrow bands throughout the radio spectrum. They use all forms of encoding, including obsolete and experimental ones. 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 by power-line internet service.

Unlicensed radio services

Government-authorized personal radio services such as Citizens' Band Radio, Family Radio Service, Multi-Use Radio Service and others exist in North America 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.

Unauthorized, unlicensed radio broadcasting is known as Free or pirate radio. The main difference between the two is that a Free radio station does not advertise or make any money, while the Pirate station could not exist without adverts, payolas, etc.

Radio control (RC)

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. He was awarded U.S. patent No. 613,809 for a "Method of and Apparatus for Controlling Mechanism of Moving Vessels or Vehicles."

The electromagnetic spectrum

Radio waves are a form of electromagnetic radiation, created whenever a charged object (in normal radio transmission, an electron) accelerates with a frequency that lies in the radio frequency (RF) portion of the electromagnetic spectrum. In radio, this acceleration is caused by an alternating current in an antenna. Radio frequencies occupy the range from a few tens of hertz to three hundred gigahertz, although commercially important uses of radio use only a small part of this spectrum. 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.

Other

Energy autarkic radio technology consists of a small radio transmitter powered by environmental energy (push of a button, temperature differences, light, vibrations, etc.). A number of schemes have been proposed for Wireless energy transfer. Various plans included transmitting power using microwaves, and the technique has been demonstrated. (See Microwave power transmission). These schemes include, for example, solar power stations in orbit beaming energy down to terrestrial users.

Music radio

Music radio is a radio format in which music is the main broadcast content. After television replaced old time radio's dramatic content, music formats became dominant in many countries. Radio drama and comedy continue, often on public radio.

Music drives radio technology, including wide-band FM and modern digital radio systems such as digital radio mondiale.

How it works

The radio station provides programming to attract listeners, and profits by selling advertising.

Young people are targeted by advertisers because their product preferences can be changed more easily. Therefore, the most commercially successful stations target young audiences.
The programming usually cycles from the least attractive item, to most attractive, followed by commercials. The purpose of this plan is to build listener interest during the programming.

Because dead air does not attract listeners, the station tries to fill its broadcast day with sound. Audiences will only tolerate a certain number of commercials before tuning away. In some regions, government regulators specify how many commercials can be played in a given hour.

Music is the main program item. There are several standard ways of selecting the music, such as free-form, top-40, album-oriented rock, and Jack. These can be applied to all types of music.

Jingles are radio's equivalent of neon signs. Jingles are brief, bright pieces of choral music that promote the station's call letters, frequency and sometimes disc-jockey or program segment. Jingles are produced for radio stations by commercial specialty services such as JAM [1], in Texas.

Jingles are often replaced by recorded voiceovers (called "stingers").

In order to build station loyalty, the station announces time, station call letters and frequency as often as six times per hour. Jingles and stingers help give the station a branded sound in a pleasant, minimal amount of air-time. The legal requirement for station identification in the U.S. is once per hour, approximately at the top of the hour, or at the conclusion of a transmission.
News, time-checks, real-time travel advice and weather reports are often valuable to listeners. The news headlines and station identification are therefore given just before a commercial. Time, traffic and weather are given just after. The engineer typically sets the station clocks to standard local time each day, by listening to WWV or WWVH (see atomic clock).

These segments are less valued by the most targeted market, young people, so many stations shorten or omit these segments in favor of music.

While most music stations that offer news reports simply "tear and read" news items (from the newswires or the Internet), larger stations (generally those affiliated with news/talk stations) may employ an editor to rewrite headlines, and provide summaries of local news. Summaries fit more news in less air-time. Some stations share news collection with TV or newspapers in the same media conglomerate. An emerging trend is to use the radio station's web site to provide in-depth coverage of news and advertisers headlined on the air. Many stations contract with agencies such as Smartraveler and AccuWeather for their weather and traffic reports instead of using in-house staff.

Most radio stations maintain a call-in telephone line for promotions and gags, or to take record requests. DJs generally answer the phone and edit the call during music plays. Some stations take requests by e-mail and online chat.

The value of a station's advertising is set by the number, age and wealth of its listeners. Arbitron, a commercial statistical service, historically used listener diaries to statistically measure the number of listeners. Arbitron diaries were collected on Thursdays, and for this reason, most radio stations have run special promotions on Thursdays, hoping to persuade last-minute Arbitron diarists to give them a larger market-share. Arbitron contractually prevents mention of its name on the air.

Promotions are the on-air equivalent of lotteries for listeners. Promotional budgets usually run about $1 per listener per year. In a large market, a successful radio station can pay a full time director of promotions, and run several lotteries per month of vacations, automobiles and other prizes. Lottery items are often bartered from advertisers, allowing both companies to charge full prices at wholesale costs. For example, cruising companies often have unused capacity, and when given the choice, prefer to pay their bills by bartering cruise vacations. Since the ship will sail in any case, bartered vacations cost the cruise company little or nothing. The promotion itself advertises the company providing the prize.

Programming by time

Most music stations have DJs that play music from a playlist determined by the program director, arranged by blocks of time. Though practices differ by region and format, what follows is a typical arrangement in a North American urban commercial radio station.

The first block of the day is the "drive-time" block in the early morning (typically 5 or 6AM) to midmorning (9 to 11AM). This block usually includes news bulletins and traffic and weather advisories for commuters, as well as light comedy from the morning DJ team (many shock jocks started as or still work on drive-time radio). Some stations emphasize music, and reduce gags and call-ins in this period.

The midday block is mostly music. For a period around noon a station may play nonstop music or go to an all-request format for people eating lunch.

In the early evening, the evening rush-hour programming resembles the midday programming, but adds traffic and weather advisories for commuters. Some stations insert a short snippet of standup comedy around 5 o'clock when commuters leave work.

The evening block, if present, returns to music.

The overnight programming is generally low-key music with quiet announcing. Some stations play documentaries or even infomercials, while some others play syndicated DJs like Delilah. It is not uncommon to play more adventurous selections during late night programming blocks, since late night is generally not considered significant for ratings.

Weekends, especially Sundays, often carry different programming. Common syndicated programming includes music countdown shows from DJs such as Rick Dees and Casey Kasem, retrospective shows, and world music such as the Putumayo World Music Hour. Stations may carry shows with different genres of music such as blues or jazz. Community affairs and religious programming is often on Sunday mornings. In addition, weekend evenings are particularly specialized; a dance station might have a sponsored dance party at a local club, or a classical station may play an opera.

Many music stations in the United States perform news and timechecks only sparingly, preferring to put more music on the air. News is often restricted to the talk-heavy commuting hours. The BBC and ABC take a different approach, with all of its stations giving news updates (BBC 1xtra produces its own news segments under the name TX.)

Music formats

Some well-known music-radio formats are Top 40, Freeform Rock and AOR (Album Oriented Rock). It turns out that most other stations (such as Rhythm & Blues) use a variation of one of these formats with a different playlist. The way stations advertise themselves is not standardized. Some critical interpretation is needed to recognize classic formulas in the midst of the commercial glitz.

See List of music radio formats for further details, and note that there is a great deal of format evolution as music tastes and commercial conditions change. For example, the Beautiful music format that developed into today's Easy listening and Soft rock formats is nearly extinct due to a lack of interest from younger generations, whereas classic rock has become popular over the last 20 years or so and Jack FM has arisen only since 2000 or so.

Top 40

The original formulaic music radio format was Top 40. In this format, disc-jockeys would select one of a set of the forty best-selling singles (usually in a rack) as rated by Billboard magazine or from the station's own chart of the local top selling songs. In general, the more aggressive "Top 40" stations could sometimes be better described as "Top 20" stations. They would aggressively skirt listener boredom to play only the most popular singles.

Top 40 radio would punctuate the music with jingles, promotions, gags, call-ins, and requests, brief news, time and weather announcements and most importantly, advertising. The distinguishing mark of a traditional top-40 station was the use of a hyperexcited disc-jockey, and high tempo jingles. The format was invented in the US and today can be heard world wide. Todd Storz and Gordon McLendon invented Top 40 radio. Bill Drake and Rick Sklar have had a lasting modern influence. This is an excellent, brief history of the format..

Variants and hybrids include the freeform-like Jack FM (mentioned below under Freeform Rock) and the "Mix" formats mentioned below under Oldies. Top 40 music is heavily criticized by some music fans as being repetitive and of low quality, and is almost exclusively dominated by large media conglomerates such as Clear Channel Communications and CBS Corporation. Top 40 tends to be underrepresented on the Internet, being mostly the domain of commercial broadcasters such as Virgin Radio UK.

Some of the most famous Top 40 stations of have been Musicradio 77 WABC/New York, Boss Radio 93 KHJ/Los Angeles Musicradio 89 WLS/Chicago, and The Big 68 WRKO/Boston.

Freeform and progressive rock

A later development was freeform radio, later commercially developed as progressive rock radio, and still later even more commercially developed as AOR (Album-Oriented Rock), in which selections from an album would be played together, with an appropriate introduction.

Traditional freeform stations prided themselves on offering their disc jockeys freedom to play significant music and make significant social commentary and humor. This approach developed commercial problems because disc jockeys attracted to this freedom often had tastes substantially different from the audience, and lost audience share. Also, freeform stations could lack predictability, and listeners' loyalty could then be put at risk. Progressive rock radio (not to be confused with the progressive rock music genre) was freeform in style but constrained so that some kind of rock music was what was always or almost always played.

Responsible jocks would realize their responsibility to the audience to produce a pleasant show, and try to keep the station sound predictable by listening to other jocks, and repeating some of their music selections. WNEW-FM in New York during the 1970s exemplified this approach to progressive rock radio.

At their best, freeform stations have never been equaled for their degree of social activism, programmatic freedom, and listener involvement. However, to succeed, the approach requires genius jocks, totally in-tune with their audience, who are also committed to the commercial success of the radio station. This is a rare combination of traits. Even if such people are available, they often command extremely high salaries. However, this may be an effective approach for a new station, if talented jocks can be recruited and motivated at low salaries.

Freeform radio is particularly popular as a college radio format; offshoots include the recent (and somewhat controversial, due to its lack of on-air personalities) eclectic-pop format known as variety hits, which plays a wide assortment of mostly top-40 music from a span of several decades; and podcast radio, a mostly-talk format pioneered by Infinity Broadcasting's KYOU station in California and Adam Curry's Podcast show on Sirius Satellite Radio.

AOR (album-oriented rock)

AOR (album-oriented rock) developed as a commercial compromise between top-forties-style formulas and progressive rock radio/freeform. A program director or music consultant would select some set of music "standards" and require the playlist to be followed, perhaps in an order selected by the jock. The jock would still introduce each selection, but the jock would have available a scripted introduction to use if he was not personally familiar with a particular piece of music and its artist. Obviously a computer helps a lot in this process.

A useful, relatively safe compromise with the artistic freedom of the jocks is that a few times each hour, usually in the least commercially valuable slots of the hour, the disc-jockey can highlight new tracks that he or she thinks might interest the audience. The audience is encouraged to comment on the new tracks, allowing the station to track audience tastes. The freedom to introduce new artists can help a station develop its library.

Significant AOR offshoots include classic rock and adult album alternative.

Oldies, standards, and classic rock

Classic rock or oldies formats have been described as having the weakness of not playing new artists. This is true in a creative sense, but not a commercial one. Stations will not get good ratings or revenue if they frequently play songs unfamiliar to their audience. This is why "Top 40" stations played only the biggest hits and why oldies and classic rock formats do the same for the eras they cover. Nevertheless, there seems to be a cottage industry of Internet stations specializing in specific forms of classic rock and oldies, particularly psychedelic rock and progressive rock.

The oldies and classic rock formats have a strong niche market, but as the audience becomes older the station becomes less attractive to advertisers. Advertisers perceive older listeners as set in their brand choices and not as responsive to advertising as younger, more impulsive listeners. Oldies stations must occasionally change to more youthful music formats; as a result, the definition of what constitutes an "oldies" station has gradually changed over the years. This is why many oldies stations, like WCBS-FM in New York City and WJMK in Chicago, have switched over to the younger-orientated Jack FM format in recent years — although WCBS-FM reverted back to its oldies format on July 12, 2007, and the "Jack FM" format was moved to its HD2 subchannel.

This preference for younger listeners caused the decline of the "Big Band" or "Standards" music formats that covered music from the 1930s to the 1950s. As the audience grew too old for advertisers, the radio stations that carried these formats saw a sharp loss of ratings and revenue. This left them with no choice but to adopt more youthful formats, though the Standards format (also known as the Great American Songbook from the series of albums produced by rocker Rod Stewart) has undergone something of an off-air revival, with artists such as Stewart, Tony Bennett and Queen Latifah putting their own interpretation on the music.

During the mid-to-late-'90s, the "Mix" format -- a loosely-defined mixture of Top-40 and classic rock with something of an emphasis on adult contemporary music -- began to appear across the country. While the format has no particular standard identity, most "mix" stations have rotations consisting largely of pop and rock music from the '80s and '90s (and often the '70s), with some current material mixed in. In addition, stations devoted to the pop music of the '70s, '80s, and '90s on their own have developed as the audiences that grew up with that music grew older and nostalgic for the sounds of their youth.

Classical, pop, easy-listening, jazz, dance

These formats all have small but very loyal audiences in the largest markets. Most follow formats similar to the above (Top 40s, Freeform, AOR and Oldies), except with a different playlist. Public service stations following these formats tend to be "freeform" stations.

Classical music radio is just as it sounds -- radio designed to appeal to the listener of classical music. internet classical Most classical stations specialize primarily in instrumental classical music and chamber music, though there are more special interest classical stations (often found through media such as satellite radio or internet radio) that carry classical pop music or operatic music.

Easy listening and Adult Contemporary are related formats that play largely down-tempo pop music of various styles. The difference is mostly in the era and styles covered -- Easy Listening is mostly older music done in the style of standards from the early 20th century (typical artists include Johnny Mathis and Frank Sinatra) internet streaming combined with Big Band music and more modern performers in the same style such as Céline Dion and Josh Groban, while Adult Contemporary focuses more on newer pop music from the 1970s on. An ancestor to the easy listening format is Beautiful Music, a now-rare format (though XM features one channel of it, called Sunny) focusing mostly on smooth jazz or classical arrangements of pop music and original compositions in a similar vein. Perhaps the best-known Adult Contemporary station currently in operation is WLTW in New York City, better known as 106.7 Lite FM.

Jazz stations generally play either traditional jazz forms or smooth jazz. The jazz station, more than any other except the college station, is stereotyped as having a small listenership and a somewhat overly highbrow on-air personality, and many are college-run stations. California State University Long Beach sponsors KJAZZ 88.1, which has a fairly significant online listenership as well. Two very well-known smooth jazz stations are WNUA in Chicago and 94.7 The Wave in Los Angeles, both of which were introduced in 1987, and still continue to enjoy tremendous success in the format today.

Dance music is a niche, and so-called "rhythmic pop" stations have had a fierce but not always commercially sustainable following. There was a wide spectrum of disco-format radio stations during the late '70s, but virtually all of them died out during the disco backlash; WXKS in Boston is one of the few notable survivors, now a Clear Channel Communications-owned top-40 station of considerable influence. Nevertheless there are a large number of dance music stations available both on the internet and on satellite radio, mostly specializing in various forms of electronica. Both major US satellite radio services include disco stations.

Alternative and modern rock

Rock music has a long and honorable radio tradition going back to DJs like Wolfman Jack and Alan Freed, and as a result variations on rock radio are fairly common. The classic rock and oldies formats are discussed above; in addition to those, however, there are several genres of music radio devoted to different aspects of modern rock music. Alternative rock grew out of the grunge scene of the late '80s and early '90s and is particularly favored by college radio and adult album alternative stations; there is a strong focus on songwriters and bands with an outsider sound or a more sophisticated sound than the "three chord wonder" cliché. Meanwhile, other stations focus on heavy metal, punk rock, or the various post-punk and pop-influenced sounds known collectively as "modern rock".

Narrow-interest rock stations are particularly common on the Internet and satellite radio scenes, broken down into genres such as punk, metal, classic rock, indie music, and the like. There is a general feeling among radio connoisseurs that rock radio is becoming badly watered down by big corporate ownership, leading to a considerable do-it-yourself spirit.

Country

While stereotyped as rural music, the Country music format is common and popular throughout the United States and in some other countries. Emphasis is generally on current pop country, though stations specializing in older country music have popped up here and there. Country has been a popular radio format since the early days of music radio. Country stations play a mix of music from Classic country to Hot Country and anywhere in between.

Urban (hip-hop/R&B)

The explosive rise in popularity during the 1980s of rap music has led to a large number of radio stations specializing in rap/hip-hop and R&B music (with the exception of classic R&B such as Motown, which is as often as not the province of Oldies stations). This format is popular among all ethnic groups and social classes.

Public radio formats

Some music radio is broadcast by public service organizations, such as National Public Radio or the BBC.

Community Radio

Community radio often relies heavily on the music format because it is relatively cheap and generally makes for easy listening. A prime example of this is Australia's premier community radio station 104.1 Territory FM.

Dance music radio

Dance music radio focuses on live DJ sets and hit singles from genres of techno, house, electro, drum and bass, UK garage and big beat. While some stations play all kinds of electronic dance music, others (mainly pirate radio stations) focus on particular genres. This format is popular in England, Germany, Netherlands and some other countries.

Regional differences

Outside of English-speaking world, several radio formats built around local musical genres are popular. Examples include Portuguese Fado and Russian Shanson.

Cost of programming

Stations usually adopt a music format to gain the greatest number of listeners for the least expense. Since the content has already been produced, the station merely adds the low-cost on-air programming between records.

Music radio stations pay music-licensing fees to licensing agencies such as ASCAP and BMI. Commercial stations often get their CDs free, but still pay royalties to play it on air. Some small neighborhood stations play unlisted locally-produced music, and avoid these fees.

Licensing issues nearly destroyed early Internet radio. In the U.S., Congress intervened with a royalty structure that was expensive to small independent operators, but easier than the RIAA's standard scale. Both XM and Sirius provide commercial packages allowing exclusive license-free use (though not rebroadcast) of their music programming by businesses

Commercial radio

Commercial stations charge advertisers for the estimated number of listeners. The larger the audience, the higher the stations' rate card can be for commercial advertising.
Commercial stations program the format of the station to gain as large a slice of the demographic audience as possible.

A station's value is usually measured as a percentage of market share in a market of a certain size. The measurement in U.S. markets has historically been by Arbitron, a commercial statistical service that uses listener diaries. Arbitron diaries were historically collected on Thursdays, and for this reason, most radio stations have run special promotions on Thursdays, hoping to persuade last-minute Arbitron diarists to give them a larger market-share. Stations are contractually prohibited from mentioning Arbitron on the air.

Market share is not always a consideration, because not all radio stations are commercial. Public radio is funded by government and private donors. Since most public broadcasting operations don't have to make a profit, no commercials are necessary.

Also, Satellite radio either charges subscribers or is operated by a public broadcasting service. Therefore, satellite radio rarely carries commercials or tries to raise money from donors. The lack of commercial interruptions in satellite radio is an important advantage. Often the only breaks in a satellite music station's programming are for station identification and DJ introductions.

Internet radio stations exist that follow all of these plans.

Much early commercial radio was completely freeform; this changed drastically with the payola scandals of the 1950s. As a result, DJs seldom have complete programming freedom.

Occasionally a special situation or highly respected, long established personality is given such freedom. Most programming is done by the program director. Program directors may work for the station or at a central location run by a corporate network. The DJ's function is generally reduced to introducing and playing songs. Many stations target younger listeners, because advertisers believe that advertising can change a younger person's product choice. Older people are thought to be less hard to change. Music radio has several possible arrangements. Originally, it had blocks of sponsored airtime that played music from a live orchestra. In the 1930s, phonograph records, especially the single, let a disc jockey introduce individual songs, or introduce blocks of songs. Since then, the program has been arranged so that commercials are followed by the content that is most valuable to the audience.

Programming is different for non-traditional broadcasting. The Jack FM format eliminates DJs entirely, as do many internet radio stations. The music is simply played. If it is announced, it is by RDS (for FM broadcast) or ID3 tags (for Internet broadcast). Satellite radio usually uses DJs, but their programming blocks are longer and not distinguished much by the time of day. In addition, receivers usually display song titles, so announcing them is not needed.

Internet and satellite broadcasting are not considered public media, so treaties and statutes concerning obscenity, transmission of ciphers and public order do not apply to those formats. So, satellite and internet radio are free to provide sexually explicit, coarse and political material.

Typical providers include Playboy Radio, uncensored rap and hard rock stations, and "outlaw" country music stations.

The wide reach and selective, non-broadcast usage of the internet allows programmers access to special interest audiences. As a result, both mainstream and narrow-interest webcasts flourish; in particular, electronic music stations are much more common on the Internet than they are in satellite or broadcast media.

Music radio and culture

Music radio, particularly top 40, has often acted as both a barometer and an arbiter of musical taste, and radio airplay is one of the defining measures of success in the mainstream musical world. In fact, the rise of rock music to popularity is intimately tied to the history of music radio.

Early forms of rock had languished in poor areas of the South. It was enjoyed mostly by rural blacks, with notable exposure in Memphis, Tennessee due to the all African American programming of WDIA. Rock music entered the mainstream during the 1950s because of controversial white DJs such as Dewey Phillips and Wolfman Jack with an appreciation for black music.

For many years, many listeners have been dissatisfied with the content of radio programming since the decline of early free form rock radio. The popularity of offshore pirate radio stations in the United Kingdom was an early symptom of frustration with the often overly safe and occasionally politicized playlists of commercial radio.

The growth of Internet radio from a small experimenter's toy in the mid-90s to a huge phenomenon allowing both small do-it-yourselfers and large commercial stations to make their offerings available worldwide was seen as a threat to over-the-air music broadcasting, and was nearly shut down by onerous licensing demands made by the recording industry. Meanwhile, the rise of satellite radio services as a major competitor have brought many of the advantages of Internet radio to an increasingly mobile listening public, including lack of censorship, greater choice, a more eclectic approach to format programming, and static-free digital sound quality.

Indeed, one-size-fits-all programming is no longer seen as tenable by some, as the diversity of musical tastes among the listening public have created a proliferation of radio formats in what some might call a form of narrowcasting.

Music scheduling system

Music scheduling systems are employed to sequence music at radio stations. Although these systems were originally implemented by manual index card methods, since the late 1970's they have exploited the efficiency and speed of digital computers. They are essential tools for broadcasting by music radio stations.

These systems are databases of the songs in active rotation at a radio station, plus an ample set of rules for sequencing them in accordance with specific policies. For example, there may be restrictions on how much time must pass between two songs by the same artist, or whether a song played during noontime today may be heard at noontime tomorrow (or not). There are also rules for what kinds of songs may succeed another according to tempos or other characteristics.

Many people believe that disc jockeys at radio stations are responsible for choosing the music which is heard on their shows. In reality, playlists for each hour of the day have usually been generated a priori by a radio station's program director using a music scheduling system. This ensures that the station programming is optimal and adheres to the policies and objectives of the station's director. These policies and objectives are usually designed to please the greatest number of people and garner the best ratings possible for the radio station.

Music scheduling is simply the function of generating a playlist. Other systems are responsible for actually reproducing the music.

The first widely used commercial music scheduler for radio is 'Selector', originally written by Dr. Andrew Economos of Radio Computing Services, Inc, in 1979. A-ware MusicMaster (called Musicscan at the time) followed in 1983. The third most commonly used music scheduler, Powergold, was release in 1988. Today, Selector, MusicMaster and PowerGold are the three most widely used music scheduling applications in broadcasting.

Scheduling, in the general radio broadcasting sense, is the placement of content against a linear timeline for transmission on a broadcast station. This content may include not only music, but also commercial advertisements, station identifiers and promotional jingles. Commercial advertisements, called 'spots' in radio lingo, are scheduled by their own separate scheduling system, called a 'traffic system' which keeps track of monetary considerations. The music schedule, non-music schedule (jingles, promos) and the commercial schedule are later merged into a single schedule (called the log) to guide what must be played on the station on a minute-by-minute basis.

When considering the internet as a new broadcast medium, the definition of scheduling could be broadened "to curate or arrange a linear playlist of video/audio content for live transmission or on-demand distribution." This would apply to both internet distribution and traditional broadcasting.

Radio format

A radio format or programming format describes the overall content broadcast on a radio station. Radio formats are frequently employed as a marketing tool, and constantly evolve. Music radio; Old Time Radio, All-news radio; Sports radio; Talk radio and Weather radio describe the operation of different genres of radio format and each format can often be sub-divided into many speciality formats.

Internet radio

Internet radio (also known as web radio, net radio, streaming radio and e-radio) is an audio broadcasting service transmitted via the Internet. Broadcasting on the Internet is usually referred to as webcasting since it is not transmitted broadly through wireless means. Internet radio involves a streaming medium that presents listeners with a continuous "stream" of audio over which they have no control, much like traditional broadcast media; in this respect, it is distinct from "on-demand" file serving. Internet radio is also distinct from podcasting, which involves downloading rather than streaming. Many Internet radio "stations" are associated with a corresponding traditional (or "terrestrial") radio station or radio network. Internet-only radio stations are independent of such associations.

Internet radio services are usually accessible from anywhere in the world—for example, one could listen to an Australian station from Europe or America. Some major networks like Clear Channel in the US and Chrysalis in the UK restrict listening to in country because of music licensing and advertising concerns.[citation needed] Internet radio remains popular among expatriates and listeners with interests that are often not adequately served by local radio stations (such as progressive rock, ambient music, folk music, classical music, and stand-up comedy). Internet radio services offer news, sports, talk, and various genres of music—everything that is available on traditional radio stations.

Internet radio technology

Streaming

The most common way to distribute Internet radio is via streaming technology using a lossy audio codec. Popular streaming audio formats include MP3, Ogg Vorbis, Windows Media Audio, RealAudio and HE-AAC (sometimes called aacPlus). The bits are "streamed" (transported) over the network in TCP or UDP packets, then reassembled and played within seconds. (The delay is referred to as lag time.)

History

Internet radio was pioneered by Carl Malamud. In 1993, Malamud launched "Internet Talk Radio" which was the "first computer-radio talk show, each week interviewing a computer expert."However, as late as 1995, this service was not available via multicast streaming; it was distributed "as audio files that computer users fetch one by one."

A November 1994 Rolling Stones concert was the "first cyberspace multicast concert." Mick Jagger opened the concert by saying, "I wanna say a special welcome to everyone that's, uh, climbed into the Internet tonight and, uh, has got into the M-bone. And I hope it doesn't all collapse."

On November 7, 1994, WXYC (89.3 FM Chapel Hill, NC USA) became the first traditional radio station to announce broadcasting on the Internet. WXYC used an FM radio connected to a system at SunSite, later known as Ibiblio, running Cornell's CU-SeeMe software. WXYC had begun test broadcasts and bandwidth testing as early as August, 1994. WREK (91.1 FM, Atlanta, GA USA) started streaming on the same day using their own custom software called CyberRadio1. However, unlike WXYC, this was WREK's beta launch and the stream was not advertised until a later date.

Some of the first Internet-only commercial radio stations emerged in 1995. NetRadio "was one of the Internet's original Webcasters," eventually "streaming more than 100 channels including both music and spoken material." Nonetheless, NetRadio Corporation ceased operations in 2001.

In 2002, the Copyright Arbitration Royalty Panel (CARP) system was initiated by the United States Congress in order to oversee decisions regarding royalty rates and terms, particularly in regard to digital distribution of audio. Many webcasters believed the 2002 proposed royalty structure to be overly burdensome and intended to disadvantage independent Internet-only stations. CARP was later phased out in favor of the Distribution Reform Act of 2004.

On May 1, 2007, the United States Copyright Royalty Board approved a rate increase in the royalties payable to performers of recorded works broadcast on the internet. This was the result of a two year proceeding, with dozens of witnesses and hundreds of documents from over twenty different parties, including large and small webcasters, NPR, college stations, and SoundExchange. The CRB was privy to private financial records and business models of the webcasters, and after reviewing the evidence and testimony, issued their decision on May 1, 2007 (which is currently under appeal). If enforced, this decision will undermine the business models of many Internet radio stations, which had previously relied on the rate of $0.000768 per song that had been unchanged from 1998-2005. These rules were scheduled to go into effect on May 1, 2007, with the first due date being July 15, 2007, and apply retroactively to January 1, 2006.

Due to these rate increases, it has been suggested that some U.S.-based Internet broadcasts should be moved to foreign jurisdictions where US royalties do not apply. "For example, Mercora, a service that allows individuals to launch their own webcasts, has established a Canadian site that they believe falls outside U.S. regulatory and royalty rules."

On 26 April 2007, the Internet Radio Equality Act (HR 2060) was proposed to reverse the CRB's decision. This bill was introduced in the U.S. House of Representatives by Congressmen Jay Inslee (D-WA) and Donald Manzullo (R-IL). Its Senate counterpart was introduced on 10 May 2007 by Senators Ron Wyden (D-Ore.) and Sam Brownback (R-Kansas). As of June 25 the legislation has over 100 Congressional co-sponsors.

Day of Silence

US Internet broadcasters organized a nationwide coalition to oppose the rate hike and in support of the Internet Radio Equality Act. On June 26, many of them participated in a "Day of Silence" — either shutting off their audio streams entirely, or replacing their streams with static, ocean sounds or other ambience, interspersed with brief public service announcements — to focus attention on the consequences of the impending rate hike.

Rhapsody, Live365, MTV, Pandora, and SHOUTcast were among the participants in the Day of Silence. Last.FM and Slacker did not participate, saying that they did not want to punish their listeners for the station's problems. Supporters of the increase in royalty rates, however, point to the fact that CBS recently purchased Last.FM for 280 million dollars, and if internet radio is to build businesses off of the product of recordings, the performers and owners of those recordings should receive fair compensation. They also point to the fact that the rates were flat from 1998 through 2005 (see above), without even being increased to reflect cost-of-living increases.

Recent SoundExchange Developments

SoundExchange recently came to an agreement with certain large webcasters regarding the minimum fees that were modified by the recent determination of the Copyright Royalty Board on May 1, 2007. While the CRB decision imposed a $500 per station or channel minimum fee for all webcasters, certain webcasters represented through DiMA negotiated a $50,000 "cap" on those fees with SoundExchange.

SoundExchange also recently offered alternative rates and terms to certain eligible small webcasters, that allows them to calculate their royalties as a percentage of their revenue or expenses, instead of at a per performance rate.

An April 2008 survey showed that, in the US, more than one in seven persons aged 25-54 years old listen to online radio each week. In 2008, 13 percent of the American population listened to the radio online, compared with 11 percent in 2004.

Internet Radio Audience Measurement

Internet radio audience measurement is any method used to determine the number of people listening to an Internet radio broadcast. This information is usually obtained from the broadcaster's audio streaming server. Icecast, Nicecast, and SHOUTcast are examples of audio streaming server softwares that provide listener statistics for audience measurement. These numbers often include information such as listeners' IP addresses, the media player they are using, how long they listened, and their computer's operating system. However, this approach differs greatly from terrestrial radio audience measurement. Demographic and psychographic information cannot be collected very easily due to geographically diverse nature of typical Internet radio audiences.

Podcast

A podcast is a series of digital-media files, which are distributed over the Internet using syndication feeds for playback on portable media players and computers. The term podcast, like broadcast, can refer either to the series of content itself or to the method by which it is syndicated; the latter is also called podcasting. The host or author of a podcast is often called a podcaster.

The term is a portmanteau of the words "iPod" and "broadcast", the Apple iPod being the brand of portable media player for which the first podcasting scripts were developed (see history of podcasting). Such scripts allow podcasts to be automatically transferred to a mobile device after they are downloaded. As more devices other than iPods became able to synchronize with podcast feeds, the term was redefined by some parties as an abbreviation for the backronym "Personal On Demand broadCASTING".

Though podcasters' web sites may also offer direct download or streaming of their content, a podcast is distinguished from other digital media formats by its ability to be syndicated, subscribed to, and downloaded automatically when new content is added, using an aggregator or feed reader capable of reading feed formats such as RSS or Atom.

History

Receiving and using podcasts

Making use of podcasts' syndication features requires appropriate software, often referred to as a podcatching client or a podcatcher. The feeds are usually distributed using RSS or Atom protocols to the podcatching client. The dominant podcatching client is Apple's iTunes player.

However, there are alternatives, including Microsoft's Zune Marketplace, Mediafly SyncClient (windows), Juice (multiplatform), Doppler (Windows), Podget (Linux) and Podracer (Linux). Some established audio players, such as Amarok, Winamp and Mediamonkey also offer (sometimes limited) podcatching functionality. Podcasts are also available directly on emerging internet-enabled devices, such as the chumby.

Specifically on iTunes, there are wide variety of podcasts available that range from music, comedy or informational podcasts that can either be in audio or video format.
Many podcasts also allow users to direct download, by giving a link to the audio file in an RSS feed or web page.

Podcasts are most often listened to on an MP3 player, but they can also be heard on a computer using media player software. Links are often also included on the podcast's website, so that the podcast can be sampled without the necessity of a subscription, and to encourage users who are not familiar with the concept of a podcast. VoIP technology can also be used for podcasts.

Radio network

A radio network is a network system which distributes programming to multiple stations simultaneously, or slightly delayed, for the purpose of extending total coverage beyond the limits of a single broadcast signal. The resulting expanded audience for programming essentially applies the benefits of mass-production to the broadcasting enterprise. A radio network has two sales departments, one to package and sell programs to radio stations, and one to sell the audience of those programs to advertisers.

Most radio networks also produce much of their programming. Originally, radio networks owned some or all of the radio stations that broadcast the network's programming. Presently however, there are many networks that do not own any stations and only produce and/or distribute programming. Similarly station ownership does not always indicate network affiliation. A company might own stations in several different markets and purchase programming from a variety of networks.

Radio networks rose rapidly with the growth of regular broadcasting of radio to home listeners in the 1920s. This growth took various paths in different places. In Britain the BBC was developed with public funding, in the form of a broadcast receiving license, and a broadcasting monopoly in its early decades. In contrast, in the United States of America various competing commercial networks arose funded by advertising revenue. In that instance, the same corporation that owned or operated the network often manufactured and marketed the listener’s radio.

Major technical challenges to be overcome when distributing programs over long distances are maintaining signal quality and managing the number of switching/relay points in the signal chain. Early on, programs were sent to remote stations (either owned or affiliated) by various methods, including leased telephone lines, pre-recorded gramophone records and audio tape.

The world's first all-radio, non-wireline network was claimed to be the Rural Radio Network, a group of six upstate New York FM stations that began operation in June 1948. Terrestrial microwave relay, a technology later introduced to link stations, has been largely supplanted by coaxial cable, fiber, and satellite, which usually offer superior cost-benefit ratios.
Many early radio networks evolved into Television networks.

Radio syndication

Radio syndication generally works the same way as in television, except that radio stations usually are not organized into strict affiliate-only networks. Radio networks generally are only distributors of programming, and individual stations (though often owned by large conglomerates) decide which shows to carry from a wide variety of networks and independent providers. As a result, radio networks like Westwood One or Premiere Radio Networks, despite their influence in broadcasting, are not as recognized among the general public as television networks like CBS or ABC. Some examples of widely-syndicated commercial music programs include weekly countdowns like Rick Dees' Weekly Top 40, the American Top 40, the Canadian Hit 30 Countdown, and the nightly program, Delilah, heard on many U.S. stations.

Syndication is particularly popular in talk radio. While syndicated music shows (with the exception of some evening and overnight shows such as Delilah mentioned above) tend to air once a week and mostly recorded, most popular talk radio programs are syndicated daily and live. Also, with a relative dearth in 24-hour talk radio networks, most radio stations are free to assemble their own lineup of talk hosts as they so choose. Examples of syndicated talk programs are Premiere Radio Networks' Rush Limbaugh Show, Talk Radio Network's Savage Nation, and ABC Radio Networks' Imus in the Morning.

National Public Radio, Public Radio International, and American Public Media all sell programming to local public radio member stations in the U.S., in contrast to true public radio networks like Canada's CBC, which owns all of its stations. Two independently-produced, non-commercial syndicated programs, heard on hundreds of community radio and indie radio stations, are Alternative Radio and Pacifica's Democracy Now!.

Some radio programs are also offered on a barter system usually at no charge to the radio station. The system is used for live programming or preproduced programs and include a mixture of ad time sold by the program producer as well as time set aside for the radio station to sell.

National Public Radio

National Public Radio (NPR) is a privately and publicly funded non-profit membership media organization that serves as a national syndicator to 797 public radio stations in the United States.

NPR was created in 1970, following congressional passage of the Public Broadcasting Act of 1967, signed into law by President Lyndon B. Johnson, which established the Corporation for Public Broadcasting and also led to the creation of the Public Broadcasting Service. The network was founded in 1970 with 30 employees and 90 public radio stations as charter members.

NPR produces and distributes news and cultural programming. Its member stations are not required to broadcast all these programs and most public radio stations broadcast programs from all three providers. Its flagships are two drive time news broadcasts, Morning Edition and the afternoon All Things Considered; both are carried by nearly all NPR member stations and in 2002 were second and third-most popular radio programs in the country. In a Harris poll conducted in 2005, NPR was voted the most trusted news source in the US.

NPR manages the Public Radio Satellite System which distributes NPR programs and other programming from independent producers and networks such as American Public Media and Public Radio International.

All Things Considered

All Things Considered (ATC) is a news radio program in the United States, broadcast on the National Public Radio network. It was the first news program on the network, and is broadcast live worldwide through several outlets.[1]

Background

ATC programming combines news, analysis, commentary, interviews, and special features broadcast live daily from 4:00 p.m. to 6:00 p.m. Eastern Time (20:00 to 23:00 UTC), and is re-fed with updates until 10 p.m. ET (02:00 UTC). Broadcasts run about 105 minutes with local content interspersed in between to complete two hours. ATC now airs on over 560 radio stations and reaches an audience of approximately 12 million listeners each weekday, making it the third most listened to radio program in the United States after The Rush Limbaugh Show and Morning Edition. ATC is co-hosted by Robert Siegel, Michele Norris and Melissa Block.

The first broadcast of All Things Considered was to about 90 radio stations on May 3, 1971, with host Robert Conley. The first story was about Washington, D.C. and the growing anti-Vietnam War protests taking place there.

Weekend All Things Considered (WATC) is a one-hour version of the show that premiered in 1977, with host and NPR Founder Robert Conley, and is broadcast on Saturdays and Sundays. Andrea Seabrook is the host.

Format

The format is generally less rigid than that of Morning Edition, with a wider array of the type and length of stories. The length of stories tends to be longer than Morning Edition, with some stories lasting for almost 23 minutes.

The program begins with the familiar Don Voegli theme song[3] under a one-minute billboard of the stories to be covered during the hour. Then the standard five-minute NPR newscast is delivered from one minute to six minutes past the hour. The newscast offers a cutaway at four after, allowing stations to cover the last 2.5 minutes with evening rush-hour news and traffic reports. For those stations that run the newscast untouched, a thirty-second music bed follows instead.

The first, or "A" segment, begins at 06:30 after the hour. It features important news stories, although not necessarily the most important news stories of the day. Often it is here that the most significant interviews or developing stories are placed. Segment A runs 12:28 in duration, and closes out at nineteen minutes after with a ninety-second station break.

At 20:30 past the hour, ATC picks back up with Segment B. This segment, which runs 7:48, features more news and analysis, and often contains lighter stories and commentary. Segment B breaks for the half-hour at 28:20 past. The program goes into a local break until half past.

At the bottom of the hour, ATC resumes with a "host return". In the thirty-second return, the host or hosts discuss what's coming up in the remaining half-hour and intro the news. 30:30 brings a four-minute newscast followed by a sixty-second local break.

Segment C kicks off at 35:30 past the hour, and runs 12:58. Long feature stories are heard here, or as many as four shorter stories or commentaries may be heard as well. The last four minutes of the second hour Segment C (beginning at 44:30) is a designated cutaway for stations to run local commentary or features. Segment C ends at 48:30 after the hour, and another ninety-second break ensues. Occasionally, the show will "break format" and place a long, 23-minute story in the "C" and "D" segments with no local break at all.

Segment D starts at 50:00 after, and concludes the hour. Unlike Morning Edition, there is no set format for this segment, although usually the second hour will contain an arts, culture, or lighter news story in this segment. Other times, hard news otherwise not fitting in the program may be placed here.

Stations receive a preliminary rundown before each broadcast (usually a few minutes before 4:00 p.m. Eastern) denoting the timing and placement of stories so they can schedule local content as appropriate. This rundown is updated as stories change until the feed ends at 10 p.m. ET. As with Morning Edition, two hours of content are scheduled for each program. After 6 p.m. Eastern, the feed repeats the earlier hours for the Midwest and West Coast, although information is updated through the evening as appropriate.

Awards

Major awards won by the show include the Ohio State Award, the Peabody Award, the Overseas Press Club Award, the DuPont Award, the American Women in Radio and Television Award and the Robert F. Kennedy Award. In 1993, the show was inducted into the Radio Hall of Fame, the first public radio program to be given that honor.

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