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19-591: VOLMET (French origin vol (flight) and météo (weather report)), or meteorological information for aircraft in flight , is a worldwide network of radio stations that broadcast TAF , SIGMET and METAR reports on shortwave frequencies, and in some countries on VHF too. Reports are sent in upper sideband mode, using automated voice transmissions. Pilots on international routes, such as North Atlantic Tracks , use these transmissions to avoid storms and turbulence, and to determine which procedures to use for descent, approach, and landing. The VOLMET network divides

38-434: A concept called trunking is commonly used to achieve better efficiency of radio spectrum use and provide very wide-ranging coverage with no switching of channels required by the mobile radio user as it roams throughout the system coverage. Trunking of two-way radio is identical to the concept used for cellular phone systems where each fixed and mobile radio is specifically identified to the system controller and its operation

57-600: 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 receiver license , and a broadcasting monopoly in its early decades. In contrast, in the United States various competing commercial broadcasting networks arose funded by advertising revenue. In that instance,

76-598: Is known as leased access . Other programming (particularly on cable television) is produced by companies operating in much the same manner as advertising-funded commercial broadcasters, and they (and often the local cable provider) sell commercial time in a similar manner. The FCC's interest in program control began with the chain-broadcasting investigation of the late 1930s, culminating in the "Blue Book" of 1946 , Public Service Responsibility For Broadcast Licensees . The Blue Book differentiated between mass-appeal sponsored programs and unsponsored "sustaining" programs offered by

95-540: Is switched by the controller. The broadcast type of 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 radio programming or information 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

114-470: Is the broadcasting of television programs and radio programming by privately owned corporate media, as opposed to state sponsorship, for example. It was the United States' first model of radio (and later television) during the 1920s, in contrast with the public television model during the 1930s, 1940s, and 1950s, which prevailed worldwide, except in the United States, Mexico, and Brazil, until

133-449: The audience measurement of a station or network. This makes commercial broadcasters more accountable to advertisers than public broadcasting , a disadvantage of commercial radio and television. In Europe, commercial broadcasting coexists with public broadcasting (where programming is largely funded by broadcast receiver licenses , public donations or government grants). In the UK, Sky UK

152-477: The 1980s. Commercial broadcasting is primarily based on the practice of airing radio advertisements and television advertisements for profit. This is in contrast to public broadcasting , which receives government subsidies and usually does not have paid advertising interrupting the show. During pledge drives , some public broadcasters will interrupt shows to ask for donations. In the United States, non-commercial educational (NCE) television and radio exist in

171-712: The Aviation routine weather reports (METAR) of specific airports. Radio network The two-way type of radio network shares many of the same technologies and components as the broadcast-type radio network but is generally set up with fixed broadcast points ( transmitters ) with co-located receivers and mobile receivers/transmitters or transceivers . In this way both the fixed and mobile radio units can communicate with each other over broad geographic regions ranging in size from small single cities to entire states/provinces or countries. There are many ways in which multiple fixed transmit/receive sites can be interconnected to achieve

190-630: The US and some Latin American countries. Commercial broadcasting is the dominant type of broadcasting in the United States and most of Latin America. "The US commercial system resulted from a carefully crafted cooperation endeavor by national corporations and federal regulators." The best-known commercial broadcasters in the United States today are the ABC , CBS , Fox , and NBC television networks , based in

209-460: The United States. Major cable television in the United States operators include Comcast , Charter Communications and Cox Communications . Direct-broadcast satellite (DBS) services include DirecTV and Dish Network . In an hour of broadcast time on a commercial broadcasting station, 10 to 20 minutes are typically devoted to advertising . Advertisers pay a certain amount of money to air their commercials , usually based upon program ratings or

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228-508: 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 stations that broadcast the network's radio format 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

247-444: The form of community radio ; however, premium cable services such as HBO and Showtime generally operate solely on subscriber fees and do not sell advertising. This is also the case for the portions of the two major satellite radio systems that are produced in-house (mainly music programming). Radio broadcasting originally began without paid commercials. As time went on, however, advertisements seemed less objectionable to both

266-746: The public and government regulators and became more common. While commercial broadcasting was unexpected in radio, in television it was planned due to commercial radio's success. Television began with commercial sponsorship and later transformed to paid commercial time. When problems arose over patents and corporate marketing strategies, regulatory decisions were made by the Federal Communications Commission (FCC) to control commercial broadcasting. Commercial broadcasting overlaps with paid services such as cable television , radio and satellite television . Such services are generally partially or wholly paid for by local subscribers and

285-475: The radio networks. This sustained programming, according to the Blue Book, had five features serving the public interest: Commercial time has increased 31 seconds per hour for all prime time television shows. For example, ABC has increased from 9 minutes and 26 seconds to 11 minutes and 26 seconds. Programming on commercial stations is more ratings-driven— particularly during periods such as sweeps in

304-434: The range of coverage required by the jurisdiction or authority implementing the system: conventional wireless links in numerous frequency bands, fibre-optic links, or microwave links. In all of these cases the signals are typically backhauled to a central switch of some type where the radio message is processed and resent (repeated) to all transmitter sites where it is required to be heard. In contemporary two-way radio systems

323-537: 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

342-500: The world into specific regions, and individual VOLMET stations in each region broadcast weather reports for specific groups of air terminals in their region at specific times, coordinating their transmission schedules so as not to interfere with one another. Schedules are determined in intervals of five minutes, with one VOLMET station in each region broadcasting reports for a fixed list of cities in each interval. These schedules repeat every hour. An aircraft in flight can obtain by VOLMET

361-613: 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 . Commercial broadcasting Commercial broadcasting (also called private broadcasting )

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