Inradio communication, used in radio andtelevision broadcasting, cell phones,two-way radios,wireless networking, andsatellite communication, among numerous other uses, radio waves are used to carry information across space from a transmitter to a receiver, bymodulating the radio signal (impressing an information signal on the radio wave by varying some aspect of the wave) in the transmitter. In radar, used to locate and track objects like aircraft, ships, spacecraft and missiles, a beam of radio waves emitted by a radar transmitter reflects off the target object, and the reflected waves reveal the object's location to a receiver that is typically colocated with the transmitter. In radio navigation systems such asGPS andVOR, a mobile navigation instrument receives radio signals from multiplenavigational radio beacons whose position is known, and by precisely measuring the arrival time of the radio waves the receiver can calculate its position on Earth. In wirelessradio remote control devices likedrones,garage door openers, andkeyless entry systems, radio signals transmitted from a controller device control the actions of a remote device. (Full article...)
The centimetric AI. Mk. VIII shown here on aBristol Beaufighter set the pattern for AI radars well into the 1970s.
Aircraft interception radar, orAI radar for short, is a historicalBritish term forradar systems used to equip aircraft with the means to find and track other flying aircraft. These radars are used primarily byRoyal Air Force (RAF) andFleet Air Armnight fighters andinterceptors for locating and tracking other aircraft, although most AI radars could also be used in a number of secondary roles as well. The term was sometimes used generically for similar radars used in other countries, notably the US. AI radar stands in contrast withASV radar, whose goal is to detect ships and other sea-surface vessels, rather than aircraft; both AI and ASV are often designed for airborne use.
The term was first used circa 1936, when a group at theBawdsey Manor research center began considering how to fit a radar system into an aircraft. This work led to theAI Mk. IV radar, the first production air-to-air radar system. Mk. IV entered service in July 1940 and reached widespread availability on theBristol Beaufighter by early 1941. The Mk. IV helped endthe Blitz, theLuftwaffes night bombing campaign of late 1940 and early 1941. ('Full article...)
Image 3Around 1920, radio broadcasting started to get popular. TheBrox Sisters, a popular singing group, gathered around the radio at the time. (fromHistory of radio)
Image 4Oliver Lodge's 1894 lectures on Hertz demonstrated how to transmit and detect radio waves. (fromHistory of radio)
Image 5November 5, 1919Nieuwe Rotterdamsche Courant advertisement, announcing PCGG's debut broadcast scheduled for the next evening, using narrow-band frequency modulation (FM). (fromRadio broadcasting)
Image 10Animation of ahalf-wave dipoleantenna radiating radio waves, showing theelectric field lines. The antenna in the center is two vertical metal rods connected to aradio transmitter (not shown). The transmitter applies analternating electric current to the rods, which charges them alternatelypositive (+) andnegative (−). Loops of electric field leave the antenna and travel away at thespeed of light; these are the radio waves. In this animation the action is shown slowed down tremendously. (fromRadio wave)
Image 11Frequency spectrum of a typical modulated AM or FM radio signal. It consists of a componentC at thecarrier wave frequency with themodulated information contained in two narrow bands of frequencies calledsidebands (SB) just above and below the carrier frequency. The bandwidth (BW) is the amount of spectrum occupied by the sidebands. (fromRadio)
Image 12Diagram of theelectric fields (E) andmagnetic fields (H) of radio waves emitted by amonopole radio transmittingantenna (small dark vertical line in the center). The E and H fields are perpendicular, as implied by the phase diagram in the lower right. (fromRadio wave)
Image 13Charles Logwood broadcasting at 2XG in New York City in 1916. (fromRadio broadcasting)
Image 18British Post Office engineers inspect Guglielmo Marconi's wireless telegraphy (radio) equipment in 1897. (fromHistory of radio)
Image 19Animated diagram of ahalf-wave dipole antenna receiving a radio wave. The antenna consists of two metal rods connected to a receiverR. Theelectric field (E, green arrows) of the incoming wave results in oscillation of theelectrons in the rods, charging the ends alternately positive(+) and negative(−). Since the length of the antenna is one half thewavelength of the wave, the oscillating field inducesstanding waves of voltage (V, represented by red band) and current in the rods. The oscillating currents (black arrows) flow down the transmission line and through the receiver (represented by the resistanceR). (fromRadio wave)
Image 25Radio communication. Information such as sound is converted by a transducer such as amicrophone to an electrical signal, which modulates aradio wave produced by thetransmitter. A receiver intercepts the radio wave and extracts the information-bearing modulation signal, which is converted back to a human usable form with another transducer such as aloudspeaker. (fromRadio)
... that technical issues in the minute before their November 2024BBC Radio 1 performance meant thatSouth Arcade had to set up while the presenter was announcing them?
RadioDecember 12, 2006 "...to create, expand, and maintain Wikipedia articles related to radio, including radio propagation and reception, radio programming, radio personalities, and the business of radio." (Example:Mutual Broadcasting System)
Radio StationsFebruary 15, 2005 "...to coordinate the activities of creating and maintaining articles about radio stations." (Example: Pulse FM Kingborough & Huon)
PodcastingJanuary 21, 2007 "...to make Wikipedia's knowledge of notable Podcast and podcast-related information as complete as possible." (Example:Podcast)
Amateur Radio(Inactive),August 24, 2006 "...to improve Wikipedia's articles related to Amateur radio, maintain the amateur radio category and its sub-categories for clean organization, and to produce and maintain templates for Amateur radio-related topic identification." (Example:Amateur radio)
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