A transmitter station or transmission facility is an installation used for transmitting radio frequency signals for wireless communication, broadcasting, microwave link, mobile telephone or other purposes.
A transmitter station or transmission facility is an installation used for transmitting radio frequency signals for wireless communication, broadcasting, microwave link, mobile telephone or other purposes.
The location may be chosen to fit the coverage area [1] and for VHF-UHF-applications line of sight considerations. For lower frequencies a location with good ground conductivity is required. In case of microwave link chains, stations should be in observable ranges of each other. (see Earth bulge) Computer programmes for the terrain profile and abacs are used in addition to on site observations. Avoidance of industrial noise is also taken into consideration. Another parameter may be the government regulations concerning public health requiring a minimum distance to human habitation. The distance depends on the power and the frequency of the transmitting signal. Low power stations may be in cities; higher power stations are always in rural areas. Most of the stations (especially high frequency stations) are located at high altitudes. So, both the minimum distance regulations and the line of sight criteria are met.
Stations may be housed in several buildings or a single building. In some cases the station is nothing but a small container.
They all have masts or towers to install antenna systems. In most cases, the mast is a passive structure to support the antennas. But in low frequency stations (such as AM radio), the mast itself may be the active antenna element. In such cases, the mast is isolated from the ground.(See Monopole antenna). If the mast itself is an active antenna element, the ground can be covered by a mesh of wires or metal elements to create a reflecting ground. Most of the stations also have facility to receive microwave signals from a microwave link or a telecommunications satellite, (TVRO or RRO).
Most stations use mains electricity, but they also have standby generators or solar energy panels in case of failure. [2] If the voltage of the mains fluctuates, a high power voltage regulator may be used.
Like all industrial sites, the buildings, the antenna masts, the generators, and the transmitting equipment of the stations should be grounded for personal safety against electrical shocks. On the masts and roofs, lightning rods should be used. For transmitter stations working on frequencies below 30 MHz a good grounding is required for good function and sometimes excessive grounding systems are used. In most cases, it is desirable to connect the rods to each other to form a simple Faraday cage. But in high altitude stations, the ground is usually rocky and finding an appropriate point for the grounding bus may be impossible. In such cases, very long grounding connectors may be used to find a good ground at lower altitudes.
Transmitters may be operated by government (civil or military) or private industry. Many stations are unattended and controlled by remote control equipment. Where operating personnel are required, personnel work on shifts and transportation may also be a parameter of station design. In such cases, accommodation, catering and health problems also play a part in station management. Especially in high altitude stations, snowmobiles must be used during winter.
Most AM radio transmitters are high-power equipment. Because of the relatively low frequency they use, they don't need to be located in high places. They may broadcast in LW (long wave), MW (medium wave) or SW (short wave). Since SW stations are assigned for very long distance communication (via reflections from atmospheric layers) they are usually employed for multi-language international services and there may be many SW transmitters in the same station.
TV and FM (frequency modulated ) radio transmitter stations as well as transposer stations are almost always built on top of hills. A single station may have many transmitters both for TV and FM. In rare cases, each transmitter has an antenna system. But in stations where many transmitters are used, this is not always possible, so the outputs of transmitters transmitting in the same frequency band are combined by a diplexer and applied to a single antenna system. (i.e. VHF 1, VHF 2, VHF 3, UHF). If two or more antenna systems have to be used, higher frequency antennas are mounted higher on the antenna mast. (The sequence of antenna systems on a typical TV-FM station may be from bottom to top; VHF-2, VHF-3 and UHF.) Microwave stations are also high altitude stations. Although high altitude is desirable also in GSM, the operators may use low power intracity stations for areas of high population density.
Path loss, or path attenuation, is the reduction in power density (attenuation) of an electromagnetic wave as it propagates through space. Path loss is a major component in the analysis and design of the link budget of a telecommunication system.
Line-of-sight propagation is a characteristic of electromagnetic radiation or acoustic wave propagation which means waves can only travel in a direct visual path from the source to the receiver without obstacles. Electromagnetic transmission includes light emissions traveling in a straight line. The rays or waves may be diffracted, refracted, reflected, or absorbed by the atmosphere and obstructions with material and generally cannot travel over the horizon or behind obstacles.
In electronics and telecommunications, a radio transmitter or just transmitter is an electronic device which produces radio waves with an antenna with the purpose of signal transmission up to a radio receiver. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating current, the antenna radiates radio waves.
Very high frequency (VHF) is the ITU designation for the range of radio frequency electromagnetic waves from 30 to 300 megahertz (MHz), with corresponding wavelengths of ten meters to one meter. Frequencies immediately below VHF are denoted high frequency (HF), and the next higher frequencies are known as ultra high frequency (UHF).
Medium wave (MW) is a part of the medium frequency (MF) radio band used mainly for AM radio broadcasting. The spectrum provides about 120 channels with more limited sound quality than FM stations on the FM broadcast band. During the daytime, reception is usually limited to more local stations, though this is dependent on the signal conditions and quality of radio receiver used. Improved signal propagation at night allows the reception of much longer distance signals. This can cause increased interference because on most channels multiple transmitters operate simultaneously worldwide. In addition, amplitude modulation (AM) is often more prone to interference by various electronic devices, especially power supplies and computers. Strong transmitters cover larger areas than on the FM broadcast band but require more energy and longer antennas. Digital modes are possible but have not reached momentum yet.
Medium frequency (MF) is the ITU designation for radio frequencies (RF) in the range of 300 kilohertz (kHz) to 3 megahertz (MHz). Part of this band is the medium wave (MW) AM broadcast band. The MF band is also known as the hectometer band as the wavelengths range from ten to one hectometers. Frequencies immediately below MF are denoted as low frequency (LF), while the first band of higher frequencies is known as high frequency (HF). MF is mostly used for AM radio broadcasting, navigational radio beacons, maritime ship-to-shore communication, and transoceanic air traffic control.
Radio propagation is the behavior of radio waves as they travel, or are propagated, from one point to another in vacuum, or into various parts of the atmosphere. As a form of electromagnetic radiation, like light waves, radio waves are affected by the phenomena of reflection, refraction, diffraction, absorption, polarization, and scattering. Understanding the effects of varying conditions on radio propagation has many practical applications, from choosing frequencies for amateur radio communications, international shortwave broadcasters, to designing reliable mobile telephone systems, to radio navigation, to operation of radar systems.
The 2-meter amateur radio band is a portion of the VHF radio spectrum that comprises frequencies stretching from 144 MHz to 148 MHz in International Telecommunication Union region (ITU) Regions 2 and 3 and from 144 MHz to 146 MHz in ITU Region 1 . The license privileges of amateur radio operators include the use of frequencies within this band for telecommunication, usually conducted locally with a line-of-sight range of about 100 miles (160 km).
Radio masts and towers are typically tall structures designed to support antennas for telecommunications and broadcasting, including television. There are two main types: guyed and self-supporting structures. They are among the tallest human-made structures. Masts are often named after the broadcasting organizations that originally built them or currently use them.
A mast radiator is a radio mast or tower in which the metal structure itself is energized and functions as an antenna. This design, first used widely in the 1930s, is commonly used for transmitting antennas operating at low frequencies, in the LF and MF bands, in particular those used for AM radio broadcasting stations. The conductive steel mast is electrically connected to the transmitter. Its base is usually mounted on a nonconductive support to insulate it from the ground. A mast radiator is a form of monopole antenna.
A television transmitter is a transmitter that is used for terrestrial (over-the-air) television broadcasting. It is an electronic device that radiates radio waves that carry a video signal representing moving images, along with a synchronized audio channel, which is received by television receivers belonging to a public audience, which display the image on a screen. A television transmitter, together with the broadcast studio which originates the content, is called a television station. Television transmitters must be licensed by governments, and are restricted to a certain frequency channel and power level. They transmit on frequency channels in the VHF and UHF bands. Since radio waves of these frequencies travel by line of sight, they are limited by the horizon to reception distances of 40–60 miles depending on the height of transmitter station.
A broadcast transmitter is an electronic device which radiates radio waves modulated with information content intended to be received by the general public. Examples are a radio broadcasting transmitter which transmits audio (sound) to broadcast radio receivers (radios) owned by the public, or a television transmitter, which transmits moving images (video) to television receivers (televisions). The term often includes the antenna which radiates the radio waves, and the building and facilities associated with the transmitter. A broadcasting station consists of a broadcast transmitter along with the production studio which originates the broadcasts. Broadcast transmitters must be licensed by governments, and are restricted to specific frequencies and power levels. Each transmitter is assigned a unique identifier consisting of a string of letters and numbers called a callsign, which must be used in all broadcasts.
Non-line-of-sight (NLOS) radio propagation occurs outside of the typical line-of-sight (LOS) between the transmitter and receiver, such as in ground reflections. Near-line-of-sight conditions refer to partial obstruction by a physical object present in the innermost Fresnel zone.
A television antenna is an antenna specifically designed for use with a television receiver (TV) to receive over-the-air broadcast television signals from a television station. Television reception is dependent upon the antenna as well as the transmitter. Terrestrial television is broadcast on frequencies from about 47 to 250 MHz in the very high frequency (VHF) band, and 470 to 960 MHz in the ultra high frequency (UHF) band in different countries. Television antennas are manufactured in two different types: "indoor" antennas, to be located on top of or next to the television set, and "outdoor" antennas, mounted on a mast on top of the owner's house. They can also be mounted in a loft or attic, where the dry conditions and increased elevation are advantageous for reception and antenna longevity. Outdoor antennas are more expensive and difficult to install but are necessary for adequate reception in fringe areas far from television stations. The most common types of indoor antennas are the dipole and loop antennas, and for outdoor antennas the Yagi, log periodic, and for UHF channels the multi-bay reflective array antenna.
The Wenvoe transmitting station, officially known as Arqiva Wenvoe, is the main facility for broadcasting and telecommunications for South Wales and the West Country. It is situated close to the village of Wenvoe in the Vale of Glamorgan, Wales, in the UK.
A radio transmitter or receiver is connected to an antenna which emits or receives the radio waves. The antenna feed system or antenna feed is the cable or conductor, and other associated equipment, which connects the transmitter or receiver with the antenna and makes the two devices compatible. In a radio transmitter, the transmitter generates an alternating current of radio frequency, and the feed system feeds the current to the antenna, which converts the power in the current to radio waves. In a radio receiver, the incoming radio waves excite tiny alternating currents in the antenna, and the feed system delivers this current to the receiver, which processes the signal.
A digital channel election was the process by which television stations in the United States chose which physical radio-frequency TV channel they would permanently use after the analog shutdown in 2009. The process was managed and mandated by the Federal Communications Commission for all full-power TV stations. Low-powered television (LPTV) stations are going through a somewhat different process, and are also allowed to flash-cut to digital.
The Oxford transmitting station is a broadcasting and telecommunications facility, situated on land 129.5 metres (425 ft) above Ordnance Datum to the north east of the city of Oxford, in Oxfordshire, England. It has a guyed steel lattice mast which is 154.4 metres (507 ft) in height to the top of the main steel structure. The UHF television antenna, which consist of a vertical array of transmitting panels, is mounted above the steel structure. The total height of the mast to the top of this UHF antenna is 165.7 metres (544 ft). It is owned and operated by Arqiva.
Radio is the technology of communicating using radio waves. Radio waves are electromagnetic waves of frequency between 3 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connected to an antenna which radiates the waves. They are received by another antenna connected to a radio receiver. In addition to communication, radio is used for radar, radio navigation, remote control, remote sensing, and other applications.
The Blaenplwyf transmitting station is a broadcasting and telecommunications facility located near the village of Blaenplwyf about 10 kilometres (6 mi) to the south west of the town of Aberystwyth, in Ceredigion, Wales. It was originally built by the BBC, entering service in October 1956 acting as a main transmitter for BBC Band II VHF FM radio.