Radio: Béda antarrépisi

Sanajan [[Nikola Tesla]] anu munggaran medar yén komunikasi nir-kabel bisa dilaksanakeun, persisna dina taun 1893, [[Guglielmo Marconi]] asal Italia, ngarupakeunmangrupa panimu anu munggaran ngalakukeun komunikasi radio. Manéhna ngirim jeung narima sinyal radio munggaran di Italia dina taun 1895.<br>

Kecap radio asalna tina kecap radioteleografiradioteléografi anu disebut ogé 'wireless telegraphy', anu disingket 'wireless'. Préfiks ''radio-'' dina harti pangiriman sacara nirkabel munggaran dicutat dina kecap 'radioconductor'', anu ditimukeun ku fisikawan Perancis [[Edouard Branly]] dina taun 1897 sarta dumasar kana kecap gawe ''to radiate'' (dina basa Laten "radius" hartina "pancaran cahaya, sinar").

Kiwari istilah 'wireless' meunangkeun deui popularitas alatan tumuwuhna jaringan telekomunikasi jarak pondok anu lumangsung gancang, contona [[WLAN]] ('Wireless Local AreaAréa Network'), [[WiFi]] jeung [[Bluetooth]] sarta telepon mobil, misalna [[GSM]] katut [[UMTS]]. Kiwari, istilah 'radio' mindeng nujul kana alat transceiver (alat pancar sakaligus panarima) atawa chip, sedengkeun 'wireless' nujul kana sistem jeung/atawa métode anu digunakeun pikeun komunikasi radio.

*Dina taun 1887, [[David E. Hughes]] mancarkeun kode Morse makemaké radio dina handapeun daerah [[Super low frequency]].

Dina taun 1893, di [[St. Louis, Missouri|St. Louis]], [[Missouri]], [[Nikola Tesla]] nyieun alat pikeun percobaan [[listrik]]. Biantara di hareupeun ''[[Franklin Institute]]'' di [[Philadelphia]] sarta ''[[National Electric Light Association]]'', manéhna ngajelaskeun, mintonkeun sarta ngawincik prinsip-prinsip gawé nirkabelna.

Pintonan telegrafi nirkabel munggaran hareupeun balaréa lumangsung di ruang kuliah Museummuséum Sajarah Alam Oxford University dina tanggal 14 Agustus 1894, anu dilaksanakeun ku Profésor [[Oliver Lodge]] jeung [[Alexander Muirhead]]. Dina éta pintonan, hiji sinyal radio dikirim ti gedong laboratorium Clarendon, sarta ditarima ku alat anu ditempatkeun di ruang kuliah dimaksud.

Dina taun [[1896]], Marconi dibéré [[patent]] 12039 ku [[United Kingdom|Inggris]], ''Improvements in transmitting electrical impulses and signals and in apparatus there-for''. Dina taun 1897 manéhna ngadegkeun stasiun radio munggaran di dunya di [[Isle of Wight]], [[Inggris]]. Marconi muka pabrik "nirkabel" munggaran di dunya di Hall Street, [[Chelmsford, Inggris]] dina taun 1898, anu ngagawékeun kira-kira 50 urang.

One of the first developments in the earlyéarly 20th century (1900-1959) was that [[aircraft]] used commercial AM radio stations for navigation. This continued until the earlyéarly 1960s when [[VHF omnidirectional range|VOR]] systems finally became widespreadwidespréad (though AM stations are still marked on U.S. [[aviation]] charts). In the earlyéarly 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 earlyéarly as the 1920s. Commercial television transmissions started in North America and Europe in the 1940s. In 1954, Regency introduced a pocket [[transistor]] radio, the [[Regency TR-1|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 yearsyéars, 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 radio]]s 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 [[Global Positioning System|GPS]] constellation in 1987. In the earlyéarly 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 radio]] that could become a different radio on the fly by changing software. Digital transmissions began to be applied to broadcasting in the late 1990s.

Radio munggaran digunakeun pikeun kaperluan maritim, nyaéta pikeun ngirim pesen telegraf anu maké [[kode Morse]] antara kapal laut jeung kapal laut sarta antara kapal laut jeung daratan. Para pamaké munggaran diantaranadi antarana Angkatan Laut Jepang pikeun nyilidik armada Rusia dina [[paperangan di Tsushima]] dina taun 1905. Kagunaan telegraf maritim anu paling diinget nyaéta waktu teuleumna [[RMS Titanic|RMS ''Titanic'']] dina taun 1912, diantaranadi antarana pikeun komunikasi antara para operator dina kapal nu titeuleum jeung kapal-kapal anu padeukeut sarta pikeun komunikasi jeung stasiun-stasiun di basisir pikeun ngémbarkeun anu salamet. Radio nu munggaran acan bisa mancarkeun sora atawa ucapan sarta disebut "wireless telegraph" atawa telegraf nirkabel.

Radio digunakeun pikeun ngirimkeun paréntah sarta komunikasi antara angkatan darat jeung angkatan laut dina [[Perang Dunia I]]; Jérman ngagunakeun komunikasi radio pikeun pesen diplomatik mangsa sakali waktu kabel lautna dipegatkeun ku Inggris. Amérika Sarikat ngirimkeun [[opat welas paringetan]] ti presiden [[Woodrow Wilson|Woodrow Wilson's]] ka Jérman ngagunakeun radio dina perang kasebut. Siaran radio mitembeyan ti [[San Jose, California|San Jose]] dina taun 1909 [http://www.bayarearadio.org/schneider/kqw.shtml], sarta jadi ilahar dina taun 1920-an, mangsa sumebarna alat panarima radio (radio receiver), hususna di Éropah jeung Amérika Sarikat. Sagigireun ti éta, siaran titik-ka-titik, kaasup pesen telepon sarta ''rélay'' program-program radio, sumebar dina taun 1920-an jeung 1930-an. Kagunaan lainna radio dina taun-taun saacan perang nyaéta hadirna kapal udara sarta kapal laut nu mampu ngadetéksi sarna manggihan kapal musuh maké [[radar]] (''RA''dio ''D''etection ''A''nd ''R''anging).

Kiwari, radio boga rupa-rupa wangunan, diantaranadi antarana nyaéta sagala rupa [[jaringan nirkabel]] sarta [[komunikasi mobil]] katut [[siaran]] radio. Saacan ditimukeunna [[televisi]], radio komérsial nyiarkeun lain waé warta jeung musik, tapi ogé ''drama'', ''komedi'', variety shows, jeung wangun hiburan lianna.

[[AM broadcasting|Radio siaran AM]] ngirimkeun musik jeung ucapan dina spékrum gelombang radio Frékuénsi Sedeng (MF—0.300 &nbsp;MHz nepi ka 3 &nbsp;MHz). Radio AM ngagunakeun [[modulasi amplitudo]], dimanadi mana amplitudo sinyal pamawa dirobah proporsional jeung amplitudo sora anu katangkep (di-trandusi) ku mikropon sedengkeun frékuénsina tetep henteu dirobah. Pangiriman sinyal cara kieu keuna ku gangguan listrik statik jeung interférensi lantaran kilat sarta sumber gangguan lianna anu mancar dina frékuénsi anu sarua ngarobah amplitudo sinyal anu dipancarkeun. Ukuran daya paling gedé anu dimeunangkeun pikeun stasiun radio AM di [[Amérika Sarikat]] nyaéta 50,000 watts sarta kalolobaan stasiun anu mancar sakuat ieu geus karolot; stasiun-stasiun ieu diantaranadi antarana [[WGN (AM)]], [[WJR]], sarta [[CKLW]]. Dina taun 1986 [[KTNN]] ngarupakeunmangrupa stasiun pamungkas anu narima idin operasi dina 50,000 watt.

[[FM broadcasting|Radio siaran FM]] ngirimkeun musik jeung ucapan kalayan ''kehandalan'' (''fidelity'') anu leuwih hadé tibatan radio AM. Dina [[modulasi frékuénsi]], parobahan amplitudo dina [[mikropon]] nyababkeun frékuénsi ''transmitter'' fluktuasi. Lantaran sinyal audio ngamodulasi frékuénsi lain amplitudo, mangka sinyal FM henteu keuna ku gangguan statik sarta interférensi saperti halna sinyal AM. FM dipancarkeun dina spéktrum gelombang radio Frékuénsi Luhur Pisan atawa ''Very High Frequency'' (VHF—30 &nbsp;MHz nepi ka 300 &nbsp;MHz). <!-- FM merlukeun spéktrum frekuensi radio leuwih loba batan AM sedengkeun hal ieu bisa dicumponan dina frékuénsi luhur. Akibatna, dina siaran FM bisa aya leuwih loba stasiun, anu masing-masingna ngirim informasi leuwih loba. --> Gelombang radio VHF watekna leuwih mirupa cahaya, ngarambat dina garis anu lempeng, sahingga jarak panarimaan kawates antara 50-100 mil. Dina kondisi atmosfir bagian luhur anu henteu biasa, sinyal FM kadang dipantulkeun balik ka bumi ku [[ionosfir]], ngakibatkeun [[TV/FM DX|jarak pancar FM anu jauh]]. ''Receiver'' FM keuna ku [[capture effect]], anu nyababkeun radio ngan narima sinyal anu paling kuat mangsa aya leuwih ti hiji sinyal anu datang dina frékuénsi nu sarua. ''Receiver'' FM relatif kebal tina gangguan kilat jeung interférensi.

Daya nu gedé boga mangfaat pikeun nembus wangunan, nyebar sabudeureun pasir-pasir, sarta mengkol dina luhureun horizon. Akibatna, stasiun-stasiun FM nu dayana 100,000 watt bisa sacara régulér kadéngé sajauh 100 mil (160 &nbsp;km), malah bisa leuwih jauh deui (nyaéta 150 mil, 240 &nbsp;km) lamun euwueh sinyal lianna dina frékuénsi nu sarua.

FM Sub-carrier services are secondary signals transmitted "[[piggyback]]" along with the main program. Special receivers are required to utilize these services. Analog channels may contain alternative programming, such as readingréading services for the blind, background music or stereosteréo sound signals. In some extremely crowded metropolitan areasaréas, 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 radio|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 weakerwéaker 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 AM in the shortwave High Frequency (HF—3 &nbsp;MHz to 30 &nbsp;MHz) radio spectrum for very long ranges or [[Marine VHF radio|narrowband FM in the VHF spectrum]] for much shorter ranges. Government, police, fire and commercial voice services use narrowband FM on special frequencies. Fidelity is sacrificed to use a smaller range of radio frequencies, usually five [[hertz|kHz]] of deviation, rather than the 75 &nbsp;kHz used by FM broadcasts and 25 &nbsp;kHz used by TV sound.

Civil and military HF (high frequency) voice services use [[shortwave]] radio to contact ships at seaséa, 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.

[[Mobile phone]]s transmit to a local [[cell site]] (transmitter/receiver) that ultimately connects to the public switched telephone network ([[Public switched telephone network|PSTN]]) through an optic fiber or microwave radio and other network elements. When the mobile phone nearsnéars the edge of the cell site's radio coverage areaaréa, 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 digitial material from a radio broadcast (such as a song) to a mobile phone. <br /><br />

Satellite phones use satellites rather than cell towers to communicate. They come in two types: [[Inmarsat|INMARSAT]] and [[Iridium (satellite)|Iridium]]. Both types provide world-wide coverage. INMARSAT uses geosynchronousgéosynchronous satellites, with aimed high-gain antennas on the vehicles. Iridium uses 66 Low Earthéarth Orbit satellites as the cells.

[[Television]] sends the picture as AM and the sound as FM, with the sound carrier a fixed frequency (4.5 &nbsp;MHz in the [[NTSC]] system) away from the videovidéo carrier. Analog television also uses a [[vestigial sideband]] on the videovidéo 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]] videovidéo in [[Anamorphic widescreen]] and [[MPEG-1 Audio Layer II|MPEG layer 2]] (''MP2'') audio. [[High-definition television]] is possible simply by using a higher-resolution picture, but [[H.264/MPEG-4 AVC|H.264/AVC]] is being considered as a replacement videovidéo 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.

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 eachéach 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 nearnéar cities. In some cases they used marine radiolocation beaconsbéacons, 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. [[VHF omnidirectional range|VOR]] (Very High Frequency Omnidirectional Range), systems (used by aircraft), have an antenna array that transmits two signals simultaneouslysimultanéously. A directional signal rotates like a lighthouse at a fixed rate. When the directional signal is facing north, an omnidirectional signal pulses. By measuringméasuring the difference in phase of these two signals, an aircraft can determine its bearingbéaring or radial from the station, thus establishing a line of position. An aircraft can get readingsréadings 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 bearingbéaring 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 measuringméasuring 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. The delay caused by the echo measuresméasures the distance. The direction of the beambéam determines the direction of the reflection. The polarization and frequency of the return can sense the type of surface. Navigational radars scan a wide areaaréa two to four times per minute. They use very short waves that reflect from earthéarth 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 heavyhéavy storms, as well as land and vehicles. Some can superimpose sonar data and map data from [[Global Positioning System|GPS]] position.

SearchSéarch radars scan a wide areaaréa with pulses of short radio waves. They usually scan the areaaréa two to four times a minute. Sometimes searchséarch radars use the [[doppler effect]] to separate moving vehicles from clutter. Targeting radars use the same principle as searchséarch radar but scan a much smaller areaaréa far more often, usually several times a second or more. WeatherWéather radars resemble searchséarch radars, but use radio waves with circular polarization and a wavelength to reflect from water droplets. Some weatherwéather radar use the [[Doppler effect|doppler]] to measureméasure wind speeds.

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 energizingénérgizing 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, creatingcréating a whistle-like audio tone. CW uses less than 100 &nbsp;Hz of bandwidth. CW is still used, these days primarily by [[amateur radio]] operators (hams). Strictly, on-off keying of a carrier should be known as "Interrupted Continuous Wave" or ICW or [[on-off keying]] (OOK).

[[radioteletype|Radio teletype]]s usually operate on short-wave (HF) and are much loved by the military because they createcréate 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 weatherwéather 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 repeatrepéat. A special bit pattern is used to locate the beginning of a frame.

Commercial use of spreadspréad spectrum begin in the 1980s.

[[Bluetooth]], most cell phones, and the 802.11b version of Wi-Fi eachéach use various forms of spreadspréad spectrum.

Systems that need reliability, or that share their frequency with other services, may use "coded orthogonal frequency-division multiplexing" or [[COFDM]]. COFDM breaksbréaks 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 makemaké 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 phone]]s, [[Digital Radio Mondiale]], [[Eureka 147]], and many other local areaaréa network, digital TV and radio standards.

Radio-frequency energy generated for heatinghéating of objects is generally not intended to radiate outside of the generating equipment, to prevent interference with other radio signals. [[Microwave oven]]s use intense radio waves to heathéat food. (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 sealingséaling of blood vessels. Induction [[furnace]]s are used for melting metal for [[casting]].

[[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 greatgréat 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 repeatersrepéaters. 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 overheadoverhéad of licensing. Similar services exist in other parts of the world. These radio services involve the use of handheld units.

The commonest form of unlicensed radio is known as Free or Pirate radio, the main differences being that a Free radio station does not advertise or makemaké any money, while the Pirate station could not exist without adverts, payolas, etc.

[[Radio control|Radio remote controls]] use radio waves to transmit control data to a remote object as in some earlyéarly forms of [[guided missile]], some earlyéarly TV remotes and a range of model boats, [[Radio-controlled car|cars]] and airplanes. Large industrial remote-controlled equipment such as [[crane (machine)|crane]]s and switching [[locomotive]]s now usually use digital radio techniques to ensure safety and reliability.

Radio waves are a form of electromagnetic radiation, createdcréated whenever a [[electric charge|charged]] object (in normal radio transmission, an [[electron]]) [[accelerate]]s 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)|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.<ref>''The Electromagnetic Spectrum'', University of Tennessee, Dept. of Physics and Astronomy</ref> Other types of electromagnetic radiation, with frequencies above the RF range, are [[microwave]], [[infrared]], visible [[light]], [[ultraviolet]], [[X-ray]]s and [[gamma ray]]s. 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]].

[[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 [[microwave]]s, and the technique has been demonstrated. (See [[Microwave power transmission]]). These schemes include, for example, [[solar energy|solar power]] [[Solar power satellite|stations]] in orbit beamingbéaming energy down to terrestrial users.

* L. de Forest, article in Electrical World [[22 Juni]] 1270/1 (1907), earlyéarly use of word "radio".

* White Llewellyn. ''The American Radio'' (University of Chicago Press, 1947).

* IAteacherIAtéacher: [http://www.iateacher.com/Lesson%206/L6P1-Title.htm Interactive Explanation of Radio Receiver Construction]

* [http://invention.smithsonian.org/resources/fa_clark_index.aspx George H. Clark Radioana Collection, ca. 1880 - 1950] - Archives Center, National Museummuséum of American History, Smithsonian Institution

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