Antenna height considerations

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The Aspects for Antenna heights considerations are depending upon the wave range and economical reasons.

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Longwave/low frequency antennas

At VLF, LF and MF the radio mast or tower is often used directly as an antenna. Its height determines the vertical radiation pattern. Masts and towers with heights around a quarter wave or shorter, radiate considerable power towards the sky. This allows only a small area of fade-free reception at night, because the distance at which groundwave and skywave are of comparable strength and can interfere with each other is severely restricted (approximately 40 kilometres to 200 kilometres from the transmission site, depending on frequency and ground conductivity).

Low frequency or LF is the ITU designation for radio frequencies (RF) in the range of 30 kilohertz (kHz) to 300 kHz. As its wavelengths range from ten kilometres to one kilometre, respectively, it is also known as the kilometre band or kilometre wave.

Medium frequency Frequencies between 300 kHz to 3 MHz

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 hectometer. Frequencies immediately below MF are denoted 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 masts and towers tall structure designed to support antennas

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.

For high power transmitters, masts with heights of about half the radiated wavelength are preferred because they concentrate the radiated power toward the horizon. This enlarges the distance at which selective fading occurs. However, masts with heights of around half a wavelength are much more expensive than shorter ones and often too expensive for lower power mediumwave stations.

Transmitter Electronic device that emits radio waves

In electronics and telecommunications, a transmitter or radio transmitter is an electronic device which produces radio waves with an antenna. 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.

For longwave transmitters, however, the construction of halfwave masts is infeasible in most cases, either for economic reasons or because of problems with flight safety. The only radio mast for longwave with a height of half a wavelength built to date was the Warsaw Radio Mast (which did not survive). For frequencies lower than the longwave range, masts have to be electrically enlarged by base loading coils or structures on the top, because the heights required for masts of even a quarter wavelength are too large to realize physically.

Longwave radio broadcast band

In radio, longwave, long wave or long-wave, and commonly abbreviated LW, refers to parts of the radio spectrum with wavelengths longer than what was originally called the medium-wave broadcasting band. The term is historic, dating from the early 20th century, when the radio spectrum was considered to consist of longwave (LW), medium-wave (MW), and short-wave (SW) radio bands. Most modern radio systems and devices use wavelengths which would then have been considered 'ultra-short'.

Use is not normally made of masts higher than five-eighths (5/8) of a wavelength, because such masts (except for some special constructions for high power mediumwave broadcasting) exhibit poor vertical radiation patterns. The heights of masts for mediumwave transmitters normally do not exceed the 300 metre (1000 foot) level.

Sometimes cage aerials or longwire aerials are used for LF and MF transmission. In this case the height of the tower may be greater than is usually the case. Because towers or masts used for cage or long wire aerials are grounded at the base, they are especially suitable for supporting antennas for UHF or VHF broadcasting.

A cage antenna is a radio antenna that consists of the top portion of a tower or mast and of several parallel wires, which are radially arranged around the lower part of the mast. One advantage of the cage aerial is that the supporting tower can be grounded, allowing it to be used for other radio services, such as a support for VHF or UHF antennas. A grounded tower also simplifies the installation of aircraft warning lamps. Cage aerials have been built in different variants for broadcasting stations in the longwave and mediumwave bands.

Ultra high frequency radio waves

Ultra high frequency (UHF) is the ITU designation for radio frequencies in the range between 300 megahertz (MHz) and 3 gigahertz (GHz), also known as the decimetre band as the wavelengths range from one meter to one tenth of a meter. Radio waves with frequencies above the UHF band fall into the super-high frequency (SHF) or microwave frequency range. Lower frequency signals fall into the VHF or lower bands. UHF radio waves propagate mainly by line of sight; they are blocked by hills and large buildings although the transmission through building walls is strong enough for indoor reception. They are used for television broadcasting, cell phones, satellite communication including GPS, personal radio services including Wi-Fi and Bluetooth, walkie-talkies, cordless phones, and numerous other applications.

Shortwave/high frequency antennas

For transmissions in the shortwave range, mast height has no influence on efficiency. Masts are generally used to support the antenna. Most shortwave masts are less than 100 metres high.

Antennas for commercial UHF/VHF

For transmissions in the VHF and UHF range, tower importance and value can vary depending on the area to be served. The cost of a tower must be recouped primarily through advertising carried on the broadcasts, especially where there are no license fees charged the listener. Considerations such as population density, line-of-sight signal range (affected by terrain), and the costs of tower construction and maintenance versus height, must all be weighed in choosing an ideal tower size. Often there are restrictions related to flight safety governing maximum allowable tower height. Two shorter towers may be a better option then a single taller tower. Also, a higher tower might not be useful if the signal is blocked by terrain or if all the listeners are in a concentrated area and a higher tower cannot pay for itself.

Advertising form of communication for marketing, typically paid for

Advertising is a marketing communication that employs an openly sponsored, non-personal message to promote or sell a product, service or idea. Sponsors of advertising are typically businesses wishing to promote their products or services. Advertising is differentiated from public relations in that an advertiser pays for and has control over the message. It differs from personal selling in that the message is non-personal, i.e., not directed to a particular individual. Advertising is communicated through various mass media, including traditional media such as newspapers, magazines, television, radio, outdoor advertising or direct mail; and new media such as search results, blogs, social media, websites or text messages. The actual presentation of the message in a medium is referred to as an advertisement, or "ad" or advert for short.

Terrain Vertical and horizontal dimension and shape of land surface

Terrain or relief involves the vertical and horizontal dimensions of land surface. The term bathymetry is used to describe underwater relief, while hypsometry studies terrain relative to sea level. The Latin word terra means "earth."

Antennas for point-to-point radio services

In most applications line-of-sight is required between the transmitting and receiving antennas for point-to-point services, and antennas may have to be mounted at a certain height about ground. For microwave radio systems, it is not always possible to use long transmission lines between transmitter and antenna, so towers with equipment rooms or cabinets close to the height of the antenna may be required.

Line-of-sight propagation characteristic of electromagnetic radiation or acoustic wave propagation which means waves which travel in a direct path from the source to the receiver

Line-of-sight propagation is a characteristic of electromagnetic radiation or acoustic wave propagation which means waves travel in a direct path from the source to the receiver. 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 telecommunications, a point-to-point connection refers to a communications connection between two communication endpoints or nodes. An example is a telephone call, in which one telephone is connected with one other, and what is said by one caller can only be heard by the other. This is contrasted with a point-to-multipoint or broadcast connection, in which many nodes can receive information transmitted by one node. Other examples of point-to-point communications links are leased lines, microwave radio relay and two-way radio.

Microwave transmission technology of transmitting information or energy by the use of microwaves

Microwave transmission is the transmission of information by microwave radio waves. Although an experimental 40-mile (64 km) microwave telecommunication link across the English Channel was demonstrated in 1931, the development of radar in World War II provided the technology for practical exploitation of microwave communication. In the 1950s, large transcontinental microwave relay networks, consisting of chains of repeater stations linked by line-of-sight beams of microwaves were built in Europe and America to relay long distance telephone traffic and television programs between cities. Communication satellites which transferred data between ground stations by microwaves took over much long distance traffic in the 1960s. In recent years, there has been an explosive increase in use of the microwave spectrum by new telecommunication technologies such as wireless networks, and direct-broadcast satellites which broadcast television and radio directly into consumers' homes.

Related Research Articles

Medium wave

Medium wave (MW) is the part of the medium frequency (MF) radio band used mainly for AM radio broadcasting. For Europe the MW band ranges from 526.5 kHz to 1606.5 kHz, using channels spaced every 9 kHz, and in North America an extended MW broadcast band ranges from 525 kHz to 1705 kHz, using 10 kHz spaced channels. The term is a historic one, dating from the early 20th century, when the radio spectrum was divided on the basis of the wavelength of the waves into long wave (LW), medium wave, and short wave (SW) radio bands.

Warsaw radio mast tower

The Warsaw Radio Mast was the world's tallest structure from 1974 until its collapse on 8 August 1991. It was the second tallest structure ever built, being surpassed as tallest by the Burj Khalifa, completed in 2010.

Guyed mast tall thin vertical structure that receives support from guy lines

A guyed mast is a tall thin vertical structure that depends on guy lines for stability. The mast itself has the compressive strength to support its own weight, but does not have the shear strength to stand unsupported, and requires guy lines to resist lateral forces such as wind loads and keep it upright. Guy lines are diagonal tensioned cables attached to the ground, usually spaced at equal angles about the structure's base.

Kalundborg Transmitter

Kalundborg Radio is a major transmission facility for long- and mediumwave at the harbour of Kalundborg in Denmark.

Ismaning radio transmitter architectural structure

The Transmitter Ismaning was a large radio transmitting station near Ismaning, Bavaria, Germany. It was inaugurated in 1932. From 1932 to 1934 this transmitter used a T-antenna as transmitting antenna, which was spun between two 115-metre-high free-standing wooden lattice towers, which were 240 metres apart. As this antenna had an unfavourable vertical radiation pattern, which produced much skywave resulting in a too small fading-free reception area at night, in 1934 a new antenna was installed. Therefore, one of the towers was dismantled and rebuilt on a 39 metres high wooden lattice base. While this work took place, an L-Antenna was used, which was spun between the other tower and a small auxiliary wooden tower. It became defunct in 1977 and was destroyed in 1983.

Mainflingen transmitter architectural structure

The Mediumwave transmitter Mainflingen is a mediumwave transmission facility south of the A3 motorway near Mainflingen, Hesse, Germany. Mainflingen was the first mediumwave transmitter for the radio station Deutschlandfunk. It went into service in 1962 with a transmission power of 50 kW, on a frequency of 1538 kHz, at the upper end of the mediumwave band. This frequency has a bad groundwave propagation and therefore a low range at daytime, but an excellent skywave propagation with a long range at night.

Königs Wusterhausen radio transmitter architectural structure

The Königs Wusterhausen transmitter was a large transmission facility for longwave, mediumwave and shortwave radio, located near Königs Wusterhausen southeast of Berlin, Germany. Initially built by the telegraph battalion of the German Army, operation began during World War I in 1916. On 22 December 1920, the transmission of a Christmas concert marked the birth of public broadcasting in Germany.

Mast radiator

A mast radiator is a radio mast or tower in which the entire structure functions as an antenna. This design, first used in radiotelegraphy stations in the early 1900s, is commonly used for transmitting antennas operating at low frequencies, in the VLF, LF and MF ranges, in particular those used for AM broadcasting. The metal 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.

T-antenna

A T-antenna, T-aerial, flat-top antenna, or top-hat antenna is a capacitively loaded monopole wire radio antenna used in the VLF, LF, MF and shortwave bands. T-antennas are widely used as transmitting antennas for amateur radio stations, long wave and medium wave broadcasting stations. They are also used as receiving antennas for shortwave listening.

A broadcast transmitter is a transmitter used for broadcasting, 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.

Near vertical incidence skywave, or NVIS, is a skywave radio-wave propagation path that provides usable signals in the range between groundwave and conventional skywave distances—usually 30–400 miles (50–650 km). It is used for military and paramilitary communications, broadcasting, especially in the tropics, and by radio amateurs for nearby contacts circumventing line-of-sight barriers. The radio waves travel near-vertically upwards into the ionosphere, where they are refracted back down and can be received within a circular region up to 650 km from the transmitter. If the frequency is too high, refraction fails to occur and if it is too low, absorption in the ionospheric D layer may reduce the signal strength.

In RF engineering, radial has two distinct meanings, both referring to lines which radiate from a radio antenna, but neither meaning is related to the other.

Radio frequency power transmission

Radio frequency power transmission is the transmission of the output power of a transmitter to an antenna. When the antenna is not situated close to the transmitter, special transmission lines are required.

Umbrella antenna

An umbrella antenna is a top-loaded electrically lengthened monopole antenna, consisting in most cases of a mast fed at the ground end, to which a number of radial wires are connected at the top, sloping downwards. They are used as transmitting antennas below 1 MHz, in the LF and particularly the VLF bands, at frequencies sufficiently low that it is impractical or infeasible to build a full size quarter-wave monopole antenna.

Wiederau transmitter architectural structure

The Wiederau transmitter is the oldest broadcasting facility in Saxony. It is located near Wiederau, a village which is part of the municipality of Pegau, and is used for medium-wave, FM and Television broadcasting.

Nauen Transmitter Station architectural structure

Nauen Transmitter Station in Nauen, Havelland district, Brandenburg, Germany, is the oldest continuously operating radio transmitting installation in the world. It was founded on 1 April 1906 by Telefunken engineer R. Hirsch on a 40-hectare property north of Nauen, leased from Fideikommissar Fritz Stotze. It operated as a longwave radiotelegraphy station through the end of World War 2, when invading Russian troops dismantled and removed the transmitting equipment. Since then it has been used as an international shortwave station. The original 1920 transmitter building remains.

Counterpoise (ground system)

In electronics and radio communication a counterpoise is a network of suspended horizontal wires or cables, used as a substitute for an earth (ground) connection in a radio antenna system. It is used with radio transmitters or receivers when a normal earth ground cannot be used because of high soil resistance or when an antenna is mounted above ground level, for example, on a building. It usually consists of a single wire or network of horizontal wires, parallel to the ground, suspended above the ground under the antenna, connected to the receiver or transmitter's "ground" wire. The counterpoise functions as one plate of a large capacitor, with the conductive layers of the earth acting as the other plate.

In radio systems, many different antenna types are used with specialized properties for particular applications. Antennas can be classified in various ways. The list below groups together antennas under common operating principles, following the way antennas are classified in many engineering textbooks.