This article is about radio as a technology. For other uses, including radio broadcasting as an art form, see Radio (disambiguation).
Radio is the transmission of signals, by modulation of electromagnetic waves with frequencies below those of visible light. An amateur radio station is a facility equipped for Radiocommunications in the amateur radio service. In Telecommunications, modulation is the process of varying a periodic Waveform, i Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. Frequency is a measure of the number of occurrences of a repeating event per unit Time. Light, or visible light, is Electromagnetic radiation of a Wavelength that is visible to the Human eye (about 400–700 Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space. Radio propagation is a term used to explain how Radio waves behave when they are Transmitted, or are propagated from one point on the Earth Early speculation that this required a medium of transport, called luminiferous aether, were found to be false. In the late 19th century " luminiferous aether " (or " ether " meaning light-bearing aether, was the term used to describe a medium for the propagation Information is carried by systematically changing (modulating) some property of the radiated waves, such as amplitude, frequency, or (more recently) phase. In Telecommunications, modulation is the process of varying a periodic Waveform, i 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. Demodulation is the act of removing the Modulation from an analog signal to get the original Baseband signal back
James Clerk Maxwell, a Scottish scientist, developed the theoretical basis for explaining electromagnetism. James Clerk Maxwell (13 June 1831 &ndash 5 November 1879 was a Scottish mathematician and theoretical physicist. 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. Heinrich Rudolf Hertz ( February 22, 1857 – January 1, 1894) was a German physicist who clarified and expanded the electromagnetic theory A spark-gap transmitter is a device for generating Radio frequency electromagnetic waves.
In 1893, Nikola Tesla, in America, first demonstrated the feasibility of wireless communications. Year 1893 ( MDCCCXCIII) was a Common year starting on Sunday (link will display the full calendar of the Gregorian calendar (or a Common There have already been discussions about Tesla's ethnicity on the talk page Guglielmo Marconi, an Italian inventor, was one of the first to develop workable commercial radio communication. Marchese Guglielmo Marconi mar'koni (25 April 1874 – 20 July 1937 was an Italian inventor best known for his development of a Radiotelegraph system It is supposed that he sent and received his first radio signal in Italy in 1895.
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. Lee De Forest, ( August 26, 1873 – June 30, 1961) was an American Inventor with over 300 patents to his credit (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. Wi-Fi (ˈwaɪfaɪ is the trade name for the popular wireless technology used Bluetooth is a wireless protocol utilizing short-range communications technology facilitating data transmission over short distances from fixed and/or mobile devices creating wireless g. , GSM and UMTS. GSM ( Global System for Mobile communications: originally from Groupe Spécial Mobile) is the most popular standard for Mobile phones in the 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. Radio-frequency identification ( RFID) is an automatic identification method relying on storing and remotely retrieving data using devices called RFID tags or
Although invention was long attributed to Guglielmo Marconi, the identity of the original inventor of radio, at the time called wireless telegraphy, is contentious. This article covers the main arguments about who had what part in the early development of radio Marchese Guglielmo Marconi mar'koni (25 April 1874 – 20 July 1937 was an Italian inventor best known for his development of a Radiotelegraph system This article covers the main arguments about who had what part in the early development of radio The term Wireless Telegraphy is a historic term used today as applied to early Radio Telegraph communications techniques and practices Development from a laboratory demonstration to commercial utility spanned several decades and required the efforts of many practitioners. The controversy over who invented the radio, with the benefit of hindsight, can be broken down as follows:
In 1893, in St. Louis, Missouri, Nikola Tesla made devices for his experiments with electricity. There have already been discussions about Tesla's ethnicity on the talk page Addressing the Franklin Institute in Philadelphia and the National Electric Light Association, he described and demonstrated in detail the principles of his wireless work. This article is about the science museum in Philadelphia For the Boston school see Benjamin Franklin Institute of Technology. The National Electric Light Association ( NELA) was a national United States trade association including the Operators of central Power generation  The descriptions contained all the elements that were later incorporated into radio systems before the development of the vacuum tube. This article is about the electronic device not an evacuated pipe used for experiments in Free-fall. 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. coherer was a primitive form of radio signal detector used in the late nineteenth and early twentieth centuries consisting of a capsule of metal filings in the space between Temistocle Calzecchi Onesti ( December 14, 1853 &ndash November 25, 1922) was an Italian Physicist and inventor born at Marchese Guglielmo Marconi mar'koni (25 April 1874 – 20 July 1937 was an Italian inventor best known for his development of a Radiotelegraph system 
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. Sir Oliver Joseph Lodge, FRS ( June 12, 1851 - August 22, 1940) born at Penkhull in Stoke-on-Trent and educated Alexander Muirhead, FRS, (1848-1920 born in East Saltoun, East Lothian, Scotland was an Electrical engineer specialising in 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. Year 1895 ( MDCCCXCV) was a Common year starting on Tuesday (link will display full calendar of the Gregorian calendar (or a Common year Alexander Stepanovich Popov (Александр Степанович Попов (Gregorian March 16 1859 - January 13 1906, Julian March coherer was a primitive form of radio signal detector used in the late nineteenth and early twentieth centuries consisting of a capsule of metal filings in the space between Further refined as a lightning detector, it was presented to the Russian Physical and Chemical Society on May 7, 1895. A lightning detector is a device that detects lightning produced by Thunderstorms There are three primary types of detectors ground-based systems using multiple antennas 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. Founded in 1886 as Westinghouse Electric Company and later renamed Westinghouse Electric Corporation by George Westinghouse. On Christmas Eve, 1906, Reginald Fessenden used a synchronous rotary-spark transmitter for the first radio program broadcast, from Ocean Bluff-Brant Rock, Massachusetts. Reginald Aubrey Fessenden ( October 6, 1866 &ndash July 22, 1932) born in East Bolton, Quebec, Canada, was Ships at sea heard a broadcast that included Fessenden playing O Holy Night on the violin and reading a passage from the Bible. " O Holy Night " (" Cantique de Noël " is a well-known Christmas carol composed by Adolphe Adam in 1847 to the French poem 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. WRUC (897 FM) is the campus Radio station of Union College in Schenectady, New York. 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. This article is about the radio navigation aid see VOR for other uses S. aviation charts). In the early 1930s, single sideband and frequency modulation were invented by amateur radio operators. Single-sideband modulation ( SSB) is a refinement of Amplitude modulation that more efficiently uses electrical power and bandwidth. 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. Television ( TV) is a widely used Telecommunication medium for sending ( Broadcasting) and receiving moving Images, either monochromatic 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. In Electronics, a transistor is a Semiconductor device commonly used to amplify or switch electronic signals The Regency TR-1, announced on October 18, 1954 by the Regency Division of I 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. is a multinational conglomerate corporation headquartered in Minato Tokyo, Japan, and one of the world's largest Media conglomerates with 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. A communications satellite (sometimes abbreviated to comsat) is an artificial Satellite stationed in space for the purposes of Telecommunications. 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. Digital radio describes Radio technologies which carry Information as a Digital signal, by means of a Digital modulation method In the 1970s, LORAN became the premier radio navigation system. LORAN ( LO ng R ange A id to N avigation is a terrestrial Radio navigation system using Low frequency Radio transmitters Soon, the U. S. Navy experimented with satellite navigation, culminating in the invention and launch of the GPS constellation in 1987. Global Navigation Satellite System (GNSS is the standard generic term for satellite navigation systems that provide autonomous geo-spatial positioning with global coverage Basic concept of GPS operation A GPS receiver calculates its position by carefully timing the signals sent by the constellation of GPS Satellites high above the Earth In the early 1990s, amateur radio experimenters began to use personal computers with audio cards to process radio signals. Amateur radio, often called ham radio, is both a Hobby and a service in which participants called "hams" use various types of Radio communications 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. The Defense Advanced Research Projects Agency (DARPA is an agency of the United States Department of Defense responsible for the development of new Technology A Software-Defined Radio (SDR system is a Radio communication system where components that have typically been implemented in hardware (i Digital transmissions began to be applied to broadcasting in the late 1990s.
Early uses were maritime, for sending telegraphic messages using Morse code between ships and land. Morse code is a Character encoding for transmitting telegraphic information using standardized sequences of short and long elements to represent the letters numerals The earliest users included the Japanese Navy scouting the Russian fleet during the Battle of Tsushima in 1905. The Battle of Tsushima ( Japanese: 対馬海戦 tsushima-kaisen, Цусимское сражение Tsusimskoye srazheniye) commonly known as the 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. Construction The Titanic was a White Star Line ocean liner built at the Harland and Wolff shipyard in Belfast, Ireland
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 its submarine cables were cut by the British. World War I (abbreviated WWI; also known as the First World War, the Great War, and the War to End All The United States passed on President Woodrow Wilson's Fourteen Points to Germany via radio during the war. Thomas Woodrow Wilson (December 28 1856—February 3 1924 was the twenty-eighth President of the United States. The Fourteen Points were listed in a speech delivered by President Woodrow Wilson of the United States to a joint session of the United 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). Radar is a system that uses electromagnetic waves to identify the range altitude direction or speed of both moving and fixed objects such as Aircraft, ships
Today, radio takes many forms, including wireless networks and mobile communications of all types, as well as radio broadcasting. Wireless network refers to any type of Computer network that is Wireless, and is commonly associated with a Telecommunications network whose interconnections For the band see Broadcast (band Broadcasting is the distribution of audio and/or Video signals which transmit 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. Television ( TV) is a widely used Telecommunication medium for sending ( Broadcasting) and receiving moving Images, either monochromatic Radio was unique among methods of dramatic presentation in that it used only sound. For more, see radio programming. Radio programming is the content that is broadcast by Radio stations The original inventors of radio such as Nikola Tesla and Guglielmo
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. Amplitude modulation ( AM) is a technique used in electronic communication most commonly for transmitting information via a Radio Carrier wave 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. The United States of America —commonly referred to as the Country to "Dominion of Canada" or "Canadian Federation" or anything else please read the Talk Page WGN (720 AM) is a Radio station in Chicago Illinois, USA. It is owned by the Tribune Company, which also owns the flagship WJR (760 AM) is a Radio station in Detroit, Michigan, United States. KGA, is now (as of April 2008 a sports radio station based in Spokane Washington. In 1986 KTNN received the last granted 50,000 watt license. KTNN is a Navajo Language AM Radio station broadcasting from Window Rock Arizona, the seat of the government of the Navajo Nation.
FM broadcast radio sends music and voice with higher fidelity than AM radio. See also Frequency modulation, FM band FM broadcasting is a broadcast Technology invented by Edwin Howard Armstrong that 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. The ionosphere is the uppermost part of the atmosphere, distinguished because it is Ionized by solar radiation TV DX and FM DX are two terms customarily grouped together that refer to long-distance reception of TV and FM Radio stations respectively 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. In Telecommunication, the capture effect, or FM capture effect, is a phenomenon associated with FM reception in which only the stronger of two signals at 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. WBCT (937 FM, "B-93" is a Radio station in Grand Rapids Michigan with a Country music format 7) in Grand Rapids, Michigan, runs 320,000 watts ERP, and can increase to 500,000 watts ERP by the terms of its original license. Michigan ( is a Midwestern state of the United States of America. 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. Very high frequency (VHF is the Radio frequency range from 30 MHz to 300 MHz. Nevertheless, when there were fewer FM stations competing, this station could be heard near Bloomington, Illinois, almost 300 miles (500 km) away.
FM subcarrier services are secondary signals transmitted in a "piggyback" fashion along with the main program. Subsidiary Communications Authority (SCA is the United States Federal Communications Commission 's (FCC official designation for Subcarrier channels transmitted by 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). In Telecommunication, the capture effect, or FM capture effect, is a phenomenon associated with FM reception in which only the stronger of two signals at 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. Single-sideband modulation ( SSB) is a refinement of Amplitude modulation that more efficiently uses electrical power and bandwidth. Marine VHF radio is installed on all large ships and most motorized small craft 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. The hertz (symbol Hz) is a measure of Frequency, informally defined as the number of events occurring per Second.
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. Shortwave Radio operates between the frequencies of 3000 KHz (3 Most use single sideband voice (SSB), which uses less bandwidth than AM. Single-sideband modulation ( SSB) is a refinement of Amplitude modulation that more efficiently uses electrical power and bandwidth. 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. "TETRA" redirects here For other uses see Tetra (disambiguation TErrestrial Trunked RAdio ( TETRA) (formerly known as Commercial services such as XM, WorldSpace and Sirius offer encrypted digital Satellite radio. A satellite radio or subscription radio (SR is a Digital radio signal that is broadcast by a Communications satellite, which covers a much wider geographical
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. A cell site is a term used primarily in North America for a site where antennas and electronic communications equipment are placed to create a cell in a Mobile phone network The public switched telephone network ( PSTN) is the network of the world's public circuit-switched Telephone networks in much the same way that the 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. Inmarsat plc ( is an international Telecommunications company originally operating as an Intergovernmental organization The Iridium Satellite constellation is a system of 66 active communication Satellites with spares in orbit and on the ground 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.
Television sends the picture as AM and the sound as FM, with the sound carrier a fixed frequency (4. Television ( TV) is a widely used Telecommunication medium for sending ( Broadcasting) and receiving moving Images, either monochromatic 5 MHz in the NTSC system) away from the video carrier. NTSC ( National Television System Committee) is the Analog television system used in the United States, Canada, Japan, Mexico Analog television also uses a vestigial sideband on the video carrier to reduce the bandwidth required. Single-sideband modulation ( SSB) is a refinement of Amplitude modulation that more efficiently uses electrical power and bandwidth.
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). 8VSB is the 8-level Vestigial sideband modulation method adopted for terrestrial broadcast of the ATSC digital television standard in the United States, Orthogonal frequency-division multiplexing ( OFDM) — essentially identical to Coded OFDM ( COFDM) and Discrete multi-tone modulation ( DVB-T is an abbreviation for Digital Video Broadcasting – Terrestrial; it is the DVB European-based consortium standard for the broadcast transmission of A Reed-Solomon error correction code adds redundant correction codes and allows reliable reception during moderate data loss. Reed-Solomon error correction is an Error-correcting code that works by Oversampling a Polynomial constructed from the data 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. Transport stream ( TS, TP, MPEG-TS, or M2T) is a Communications protocol for audio, video, and data A container format is a computer file format that can contain various types of data compressed by means of standardized audio/video codecs. DVD (also known as " Digital Versatile Disc " or " Digital Video Disc " - see Etymology)is MPEG-2 is a standard for "the generic coding of moving pictures and associated audio information" Anamorphic widescreen is a videographic technique utilising rectangular (wide pixels to store a Widescreen image to standard 43 aspect ratio. MPEG-1 Audio Layer II ( MP2, sometimes incorrectly called Musicam) is an Audio codec defined by ISO/IEC 11172-3 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. High-definition television (HDTV is a Digital television Broadcasting system with higher resolution than traditional television systems (standard-definition H264 is a standard for Video compression. It is also known as MPEG-4 Part 10, or MPEG-4 AVC (for Advanced Video Coding) With the compression and improved modulation involved, a single "channel" can contain a high-definition program and several standard-definition programs.
All satellite navigation systems use satellites with precision clocks. Global Navigation Satellite System (GNSS is the standard generic term for satellite navigation systems that provide autonomous geo-spatial positioning with global coverage 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. LORAN ( LO ng R ange A id to N avigation is a terrestrial Radio navigation system using Low frequency Radio transmitters VOR (Very High Frequency Omnidirectional Range), systems (used by aircraft), have an antenna array that transmits two signals simultaneously. This article is about the radio navigation aid see VOR for other uses 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. Distance Measuring Equipment (DME is a transponder-based radio navigation technology that measures distance by timing the propagation delay of VHF or UHF radio signals 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 (Radio Detection And Ranging) detects objects at a distance by bouncing radio waves off them. Radar is a system that uses electromagnetic waves to identify the range altitude direction or speed of both moving and fixed objects such as Aircraft, ships 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. Basic concept of GPS operation A GPS receiver calculates its position by carefully timing the signals sent by the constellation of GPS Satellites high above the Earth
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. The Doppler effect (or Doppler shift) named after Christian Doppler, is the change in Frequency and Wavelength of a Wave for 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 to measure wind speeds. The Doppler effect (or Doppler shift) named after Christian Doppler, is the change in Frequency and Wavelength of a Wave for
Most new radio systems are digital, see also: Digital TV, Satellite Radio, Digital Audio Broadcasting. Digital television (DTV is the sending and receiving of moving images and sound by discrete ( digital) signals in contrast to the analog signals used by A satellite radio or subscription radio (SR is a Digital radio signal that is broadcast by a Communications satellite, which covers a much wider geographical Digital Audio Broadcasting ( DAB) also known as Eureka 147, is a Digital radio technology for Broadcasting Radio stations used in 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. Morse code is a Character encoding for transmitting telegraphic information using standardized sequences of short and long elements to represent the letters numerals 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 continuous wave or continuous waveform ( CW) is an Electromagnetic wave of constant Amplitude and Frequency; and in Mathematical This article is about the electronic device not an evacuated pipe used for experiments in Free-fall. An electronic oscillator is an Electronic circuit that produces a repetitive electronic signal often a Sine wave or a Square wave. A receiver with a local oscillator would "heterodyne" with the pure radio frequency, creating a whistle-like audio tone. In Radio and Signal processing, heterodyning is the generation of new frequencies by mixing or multiplying two Oscillating waveforms CW uses less than 100 Hz of bandwidth. CW is still used, these days primarily by amateur radio operators (hams). Amateur radio, often called ham radio, is both a Hobby and a service in which participants called "hams" use various types of Radio communications Strictly, on-off keying of a carrier should be known as "Interrupted Continuous Wave" or ICW or on-off keying (OOK). On-off keying ( OOK) is a type of Modulation that represents Digital Data as the presence or absence of a Carrier wave.
Radio teletypes usually operate on short-wave (HF) and are much loved by the military because they create written information without a skilled operator. Radioteletype ( RTTY) is a Telecommunications system consisting of two or more Teleprinters using Radio as the Transmission medium. 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. Spread-spectrum techniques are methods by which Energy generated in a particular bandwidth is deliberately spread in the Frequency domain, resulting Basic concept of GPS operation A GPS receiver calculates its position by carefully timing the signals sent by the constellation of GPS Satellites high above the Earth Commercial use of spread spectrum begin in the 1980s. Bluetooth, most cell phones, and the 802. Bluetooth is a wireless protocol utilizing short-range communications technology facilitating data transmission over short distances from fixed and/or mobile devices creating wireless 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. Orthogonal frequency-division multiplexing ( OFDM) — essentially identical to Coded OFDM ( COFDM) and Discrete multi-tone modulation ( 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. Digital signal processing ( DSP) is concerned with the representation of the signals by a sequence of numbers or symbols and the processing of these signals 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. Wi-Fi (ˈwaɪfaɪ is the trade name for the popular wireless technology used Digital Radio Mondiale ( DRM) is a set of digital audio broadcasting technologies designed to work over the bands currently used for AM broadcasting, particularly Digital Audio Broadcasting ( DAB) also known as Eureka 147, is a Digital radio technology for Broadcasting Radio stations used in
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. A microwave oven, or a microwave, is a Kitchen appliance that cooks or heats Food by Dielectric heating. (Note: It is a common misconception that the radio waves are tuned to the resonant frequency of water molecules. The microwave frequencies used are actually about a factor of ten below the resonant frequency. ) Diathermy equipment is used in surgery for sealing of blood vessels. Induction furnaces are used for melting metal for casting. A furnace is a device used for Heating The name derives from Latin fornax, Oven. Casting is a manufacturing process by which a liquid material is (usually poured into a mold which
Amateur radio is a hobby in which enthusiasts purchase or build their own equipment and use radio for their own enjoyment. Amateur radio, often called ham radio, is both a Hobby and a service in which participants called "hams" use various types of Radio communications 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.
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. Citizens' Band radio ( CB) is in many countries a system of short-distance simplex radio communications between individuals on a selection of 40 channels within The Family Radio Service (FRS is an improved Walkie talkie radio system authorized in the United States since 1996 In the United States the Multi-Use Radio Service (MURS is a Two-way radio service consisting of five frequencies in the VHF Similar services exist in other parts of the world. These radio services involve the use of handheld units. The most common form of unlicensed radio 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 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. Radio control (often abbreviated to R/C or simply RC) is the use of radio signals to remotely control a device Guided Missile is a London based Independent record label set up by Paul Kearney in 1994. A radio-controlled car ( R/C car) is a powered Model car driven from a distance via a Radio control system Large industrial remote-controlled equipment such as cranes and switching locomotives now usually use digital radio techniques to ensure safety and reliability. A crane is a lifting machine equipped with a Winder, Wire ropes or Chains and sheaves that can be used both to lift and lower materials and to A locomotive is a railway Vehicle that provides the motive power for a Train.
In Madison Square Garden, at the Electrical Exhibition of 1898, Nikola Tesla successfully demonstrated a radio-controlled boat. Madison Square Garden, often abbreviated as MSG, and known colloquially as The Garden, has been the name of four Arenas in New York City.  He was awarded U. S. patent No. 613,809 for a "Method of and Apparatus for Controlling Mechanism of Moving Vessels or Vehicles. "
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. Electric charge is a fundamental conserved property of some Subatomic particles which determines their Electromagnetic interaction. The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J Radio frequency ( RF) is a Frequency or rate of Oscillation within the range of about 3 Hz to 300 GHz The electromagnetic (EM spectrum is the range of all possible Electromagnetic radiation frequencies In radio, this acceleration is caused by an alternating current in an antenna. An alternating current ( AC) is an Electric current whose direction reverses cyclically as opposed to Direct current, whose direction remains constant An antenna is a Transducer designed to transmit or Receive electromagnetic waves In other words antennas convert electromagnetic waves into 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. The hertz (symbol Hz) is a measure of Frequency, informally defined as the number of events occurring per Second.  Other types of electromagnetic radiation, with frequencies above the RF range, are microwave, infrared, visible light, ultraviolet, X-rays and gamma rays. Microwaves are electromagnetic waves with Wavelengths ranging from 1 mm to 1 m or frequencies between 0 Infrared ( IR) radiation is Electromagnetic radiation whose Wavelength is longer than that of Visible light, but shorter than that of Light, or visible light, is Electromagnetic radiation of a Wavelength that is visible to the Human eye (about 400–700 Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays X-radiation (composed of X-rays) is a form of Electromagnetic radiation. Gamma rays (denoted as &gamma) are a form of Electromagnetic radiation or light emission of frequencies produced by sub-atomic particle interactions 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. In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny Non-ionizing radiation (or esp in British English, non-ionising radiation) refers to any type of Electromagnetic radiation that does not carry enough
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. Wireless energy transfer or wireless power transmission is the process that takes place in any system where Electrical energy is transmitted from a power Various plans included transmitting power using microwaves, and the technique has been demonstrated. Microwaves are electromagnetic waves with Wavelengths ranging from 1 mm to 1 m or frequencies between 0 (See Microwave power transmission). Microwave power transmission ( MPT) is the use of Microwaves to transmit power through Outer space or the atmosphere without the need for These schemes include, for example, solar power stations in orbit beaming energy down to terrestrial users. Solar energy is the Light and radiant heat from the Sun that powers Earth 's Climate and Weather and sustains Life A solar power satellite, or SPS or Powersat, as originally proposed would be a Satellite built in High Earth orbit that uses Microwave
Glenn Hauser (born April 12, 1945 in Berkeley California) is an internationally-known DXer and Radio host from Enid Oklahoma