Mast radiator
Encyclopedia
A mast radiator is a radio mast or tower
in which the whole structure itself functions as an antenna
. This design 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
.
s insulated from the ground at the base. Steel lattice mast
s, of triangular cross-section, are the most common type. Square lattice masts and tubular masts are also sometimes used. To ensure that the tower is a continuous conductor, the tower's structural sections are electrically bonded at the joints by short copper jumpers which are soldered to each side.
At its base, the mast is usually mounted on a thick ceramic insulator, which has the compressive strength to support the tower's weight and the dielectric strength to withstand the high RF voltage applied by the transmitter. The RF
power to drive the antenna is supplied by an antenna tuner
unit, usually housed in a small building called a helix building
next to the mast, and the cable supplying the current is simply bolted to the tower. The actual transmitter
is usually located in a separate building, which supplies RF power to the helix building via a transmission line
Free-standing towers are also used as radiating structures. These towers can have a triangular or a square cross section. One of the best-known radiating towers is the Blosenbergturm
in Beromünster
, Switzerland
. Masts of glass fibre are sometimes used for some small constructions.
, demographics
for the location, and terrain. For radio systems in the longwave
and mediumwave
range the value of the height should be in the range between one sixth and five eighths of the wavelength, with favourite values at the quarter or the half of the radiated wavelength. When this is not always possible, masts with a loading coil
, 'capacity hat' or similar loading arrangement are used. The quarter-wave mast is a form of monopole antenna
.
The height of the mast determines the radiation properties. For high power transmitters in the MW range, masts with heights around half of the radiated wavelength are preferred because they focus the radiated power better to the ground than structures with heights of quarter wavelengths, which are preferred for economical reasons for low power medium wave transmitters. A focus of radiated power towards the ground is much desired on frequencies below 3 megahertz, because groundwave propagation is very stable. Masts longer than five eighths of the wavelength are normally not used, because they show bad vertical radiation patterns, so masts for mediumwave transmitters do not normally exceed 300 metres. For longwave
transmitters, however, the construction of masts with heights of half-wave wavelength is, because of economical reasons (and perhaps problems with the flight safety), in most cases impossible. The only so far realized radio mast for longwave
with a height of the half length of the radiated wavelength was the Warszawa Radio Mast at Konstantynów, Poland
. At the time of its collapse in 1991 it was the tallest manmade structure in the world, at 646.38 metres (2,120.67 ft) tall. For frequencies below longwave masts are electrically enlarged by loading coil
s or capacity hats on the top, because masts of even quarter wave length would be too high.
There is usually an antenna matching unit to match the impedance of the transmitter or feeder to the antenna. Depending on the power involved, this may be a small box or a hut or building. It will typically contain an L-network to transform the modulus of impedance, and a coil or capacitor in series with the mast connection to 'tune out' any reactive component.
At facilities with multiple masts, spacings are typically smaller, in order to fit them into the available space.
At modern transmitters or at low power transmitters situated in very small transmitter buildings the transmitter, matching unit and mast radiator can be very close together and even in the same building. This measure saves on feeders, land area and increases the efficiency of the transmitter, if only one mast radiator is in use.
At most facilities the mast radiator is on a separate base close to the antenna matching unit, but it can be sometimes set up the roof of it. This is for example the case at the main transmission mast of the Mühlacker radio transmitter and the main transmission mast of the Ismaning radio transmitter.
For a good groundwave propagation, mast radiators should be built always on a large flat area with good ground conductivity and if possible without inclination. The construction of a mast radiator on the top of a building or a tower, whose height is in the same magnitude range as the wavelengths being transmitted gives a bad groundwave propagation. So mast radiators are (in contrast to FM broadcasting antennas) normally not installed on the top of buildings or towers. Nevertheless in rare cases mast radiators for low power transmissions are installed on top of buildings. So some lighthouses like Reykjanesviti
carry a mast radiator for a longwave radio beacon on its roof. Also low-power broadcasting stations uses and used such arrangements. The best-known are WGSO in New Orleans and KSBN (AM) on the Delaney Building
in Spokane
. In Europe the low-power broadcasting station at Campobasso uses a mast radiator on a castle.
If the mast radiator is mounted on the top of the helix building, which must be over four metres in height; or the mast is grounded, with the feed being located not less than four metres above the ground, a fence is not required.
Nevertheless it is always recommended to fence in any mast radiator in order to prevent unauthorized climbing.
. Such connections include static drain chokes for lightning protection, power supplies for aircraft warning lamps
, and coaxial feeders for ancillary antennas mounted on the mast. A variety of techniques is used to 'isolate' these connections from the high RF
voltage on the mast, such as chokes
, parallel tuned circuits and coupling loops, on a base-fed mast. On a shunt-fed mast, where the base is grounded, no such measures are necessary.
far away from the transmitter site. An anti-fading aerial must reduce radiation at elevations of more than 50 degrees as much as possible.
In its simplest form it is an aerial of half wavelength. Such an aerial should be as thin as possible. In early days therefore a wire was hung up in a wood framework tower. Nowadays a radio mast is therefore used, which is fed at its foot and in a certain height. Therefore the radio mast must be insulated against ground and be divided by a separation insulator electrically in two parts, where for feeding of the upper part either a cable inside the mast construction or the ladder, which must be mounted insulated is used. The medium wave transmitters Mühlacker
, Wolfsheim
and Hamburg
use such aerials. There are also radio masts for fading reducing aerials with two separation insulators as at Ismaning
.
Because such separation insulators are more sensitive as the whole other construction of the radio mast, bigger horizontal forces, which could be generated by wind caused oscillations, should be inhibited. Therefore some radio mast with built in separation insulators have oscillation dampers just above the separation insulator. You find such device at the radio masts of the transmitters Wolfsheim
, Hamburg
and Ismaning
.
Another possibility for reducing an anti-fading aerial is the usage of dipoles hung up in a certain height above ground. A further possibility of the realization an anti-fading aerial is a circle group aerial. Therefore many mast radiators were arranged on a circle and fed in equal phase. With such facilities very flat radiation patterns could be realized, although they are very expensive, because multiple radio masts are required. Taldom transmitter
and Tulagino transmitter in Russia are obviously the only radio stations using such an antenna. In earlier days longwave transmitter Orlunda
in Sweden also used such an antenna.
at Konstantynow, Poland. It was 646.38 metres high but collapsed in 1991. Currently the masts of the Lualualei VLF transmitter, at 458.11 metres, are the tallest mast radiators insulated against ground. In contrast to the Warsaw Radio Mast, the Lualualei antenna uses extensive electrical lengthening
measures. The tallest mast radiator not using electrical lengthening may be the Hellissandur longwave radio mast
. It is 411.48 metres high.
Radio masts and towers
Radio masts and towers are, typically, tall structures designed to support antennas for telecommunications and broadcasting, including television. They are among the tallest man-made structures...
in which the whole structure itself functions as an antenna
Antenna (radio)
An antenna is an electrical device which converts electric currents into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver...
. This design is commonly used for transmitting
Transmitter
In electronics and telecommunications a transmitter or radio transmitter is an electronic device which, with the aid of an antenna, produces radio waves. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating...
antennas operating at low frequencies
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
, in the VLF
Very low frequency
225px|thumb|right|A VLF receiving antenna at [[Palmer Station]], Antarctica, operated by Stanford UniversityVery low frequency or VLF refers to radio frequencies in the range of 3 kHz to 30 kHz. Since there is not much bandwidth in this band of the radio spectrum, only the very simplest signals...
, LF
Low frequency
Low frequency or low freq or LF refers to radio frequencies in the range of 30 kHz–300 kHz. In Europe, and parts of Northern Africa and of Asia, part of the LF spectrum is used for AM broadcasting as the longwave band. In the western hemisphere, its main use is for aircraft beacon,...
and MF
Mediumwave
Medium wave is the part of the medium frequency radio band used mainly for AM radio broadcasting. For Europe the MW band ranges from 526.5 kHz to 1606.5 kHz...
ranges, in particular those used for AM broadcasting
Broadcasting
Broadcasting is the distribution of audio and video content to a dispersed audience via any audio visual medium. Receiving parties may include the general public or a relatively large subset of thereof...
. The metal mast is electrically connected to the transmitter
Transmitter
In electronics and telecommunications a transmitter or radio transmitter is an electronic device which, with the aid of an antenna, produces radio waves. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating...
. Its base is usually mounted on a nonconductive support to insulate it from the ground. A mast radiator is a form of monopole antenna
Monopole antenna
A monopole antenna is a class of radio antenna consisting of a straight rod-shaped conductor, often mounted perpendicularly over some type of conductive surface, called a ground plane. The driving signal from the transmitter is applied, or for receiving antennas the output voltage is taken,...
.
Design
Most mast radiators are built as guyed mastGuyed mast
A guyed mast is a tall thin vertical structure that receives support from guy lines.Guyed masts are frequently used for radio masts. The mast can either support aerials mounted at its top, or the entire structure itself can function as an antenna ; this is called a mast radiator...
s insulated from the ground at the base. Steel lattice mast
Lattice mast
Lattice masts, or cage masts, are a type of observation mast common on major warships in the early 20th century. They were used most prominently on American dreadnought battleships and armored cruisers of the World War I era. Observation posts were mounted on the masts and used to direct the fire...
s, of triangular cross-section, are the most common type. Square lattice masts and tubular masts are also sometimes used. To ensure that the tower is a continuous conductor, the tower's structural sections are electrically bonded at the joints by short copper jumpers which are soldered to each side.
At its base, the mast is usually mounted on a thick ceramic insulator, which has the compressive strength to support the tower's weight and the dielectric strength to withstand the high RF voltage applied by the transmitter. The RF
Radio frequency
Radio frequency is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals...
power to drive the antenna is supplied by an antenna tuner
Antenna tuner
An antenna tuner, transmatch or antenna tuning unit is a device connected between a radio transmitter or receiver and its antenna to improve the efficiency of the power transfer between them by matching the impedance of the equipment to the antenna...
unit, usually housed in a small building called a helix building
Helix Building
A helix building is a small structure at the base of a longwave or mediumwave radio transmitter. Within, there are capacitors and coils for coupling the signal from the feed cable to the antenna. Active components such as amplifiers are usually not housed in a helix building...
next to the mast, and the cable supplying the current is simply bolted to the tower. The actual transmitter
Transmitter
In electronics and telecommunications a transmitter or radio transmitter is an electronic device which, with the aid of an antenna, produces radio waves. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating...
is usually located in a separate building, which supplies RF power to the helix building via a transmission line
Transmission line
In communications and electronic engineering, a transmission line is a specialized cable designed to carry alternating current of radio frequency, that is, currents with a frequency high enough that its wave nature must be taken into account...
Free-standing towers are also used as radiating structures. These towers can have a triangular or a square cross section. One of the best-known radiating towers is the Blosenbergturm
Blosenbergturm
The Blosenbergturm is a transmitting tower in Beromünster, Canton of Lucerne, Switzerland, built in 1937 for the German language radio station DRS and radiating at an AM frequency of 531 kHz marking the bottom end of the official mediumwave broadcasting range. The Blosenbergturm has a height of...
in Beromünster
Beromünster
Beromünster is a municipality in the district of Sursee in the canton of Lucerne in Switzerland. On 1 January 2009 Gunzwil became part of Beromünster.-History:...
, Switzerland
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....
. Masts of glass fibre are sometimes used for some small constructions.
Mast height
The ideal height of a mast radiator depends on transmission frequencyRadio frequency
Radio frequency is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals...
, demographics
Demographics
Demographics are the most recent statistical characteristics of a population. These types of data are used widely in sociology , public policy, and marketing. Commonly examined demographics include gender, race, age, disabilities, mobility, home ownership, employment status, and even location...
for the location, and terrain. For radio systems in the longwave
Longwave
In radio, longwave refers to parts of radio spectrum with relatively long wavelengths. The term is a historic one dating from the early 20th century, when the radio spectrum was considered to consist of long, medium and short wavelengths...
and mediumwave
Mediumwave
Medium wave is the part of the medium frequency radio band used mainly for AM radio broadcasting. For Europe the MW band ranges from 526.5 kHz to 1606.5 kHz...
range the value of the height should be in the range between one sixth and five eighths of the wavelength, with favourite values at the quarter or the half of the radiated wavelength. When this is not always possible, masts with a loading coil
Loading coil
In electronics, a loading coil or load coil is a coil that does not provide coupling to any other circuit, but is inserted in a circuit to increase its inductance. The need was discovered by Oliver Heaviside in studying the disappointing slow speed of the Transatlantic telegraph cable...
, 'capacity hat' or similar loading arrangement are used. The quarter-wave mast is a form of monopole antenna
Monopole antenna
A monopole antenna is a class of radio antenna consisting of a straight rod-shaped conductor, often mounted perpendicularly over some type of conductive surface, called a ground plane. The driving signal from the transmitter is applied, or for receiving antennas the output voltage is taken,...
.
The height of the mast determines the radiation properties. For high power transmitters in the MW range, masts with heights around half of the radiated wavelength are preferred because they focus the radiated power better to the ground than structures with heights of quarter wavelengths, which are preferred for economical reasons for low power medium wave transmitters. A focus of radiated power towards the ground is much desired on frequencies below 3 megahertz, because groundwave propagation is very stable. Masts longer than five eighths of the wavelength are normally not used, because they show bad vertical radiation patterns, so masts for mediumwave transmitters do not normally exceed 300 metres. For longwave
Longwave
In radio, longwave refers to parts of radio spectrum with relatively long wavelengths. The term is a historic one dating from the early 20th century, when the radio spectrum was considered to consist of long, medium and short wavelengths...
transmitters, however, the construction of masts with heights of half-wave wavelength is, because of economical reasons (and perhaps problems with the flight safety), in most cases impossible. The only so far realized radio mast for longwave
Longwave
In radio, longwave refers to parts of radio spectrum with relatively long wavelengths. The term is a historic one dating from the early 20th century, when the radio spectrum was considered to consist of long, medium and short wavelengths...
with a height of the half length of the radiated wavelength was the Warszawa Radio Mast at Konstantynów, Poland
Poland
Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...
. At the time of its collapse in 1991 it was the tallest manmade structure in the world, at 646.38 metres (2,120.67 ft) tall. For frequencies below longwave masts are electrically enlarged by loading coil
Loading coil
In electronics, a loading coil or load coil is a coil that does not provide coupling to any other circuit, but is inserted in a circuit to increase its inductance. The need was discovered by Oliver Heaviside in studying the disappointing slow speed of the Transatlantic telegraph cable...
s or capacity hats on the top, because masts of even quarter wave length would be too high.
Feed arrangements
There are three ways of feeding a mast radiator from a transmitter:- Base feed: the mast is supported on an insulator, and the transmitter is connected to the mast just above it;
- Shunt feed: the mast is grounded and the transmitter feeds it via a wire connected to the mast part way up. (This is a similar approach, on a larger scale, to the 'gamma match' popular among amateur radio operatorAmateur radio operatorAn amateur radio operator is an individual who typically uses equipment at an amateur radio station to engage in two-way personal communications with other similar individuals on radio frequencies assigned to the amateur radio service. Amateur radio operators have been granted an amateur radio...
s for VHF and UHF amateur radioAmateur radioAmateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...
antennas.) - Multiple feed: the structure is divided into two (or more) sections with insulators between, each independently fed. This collinearCollinear antenna arrayIn telecommunications, a collinear antenna array is an array of dipole antennas mounted in such a manner that the corresponding elements of each antenna are parallel and collinear, that is they are located along a common line or axis....
arrangement enhances low-angle (ground wave) radiation and reduces high-angle (sky wave) radiation. This increases the distance to the mush zoneMush zoneIn mediumwave broadcasting, a mush zone is a region where the ground wave and sky wave from a transmitter are received at approximately equal signal strength, resulting in interference between the two, which will typically cause fading and distorted audio....
where the ground wave and sky wave are at similar strength at night. This type of antenna is known as an anti-fading aerial (see below).
There is usually an antenna matching unit to match the impedance of the transmitter or feeder to the antenna. Depending on the power involved, this may be a small box or a hut or building. It will typically contain an L-network to transform the modulus of impedance, and a coil or capacitor in series with the mast connection to 'tune out' any reactive component.
Location on transmission facility
At some facilities, especially the older and higher-powered installations, the mast radiator may be located at some distance of the transmitter building, in order to reduce the field strength induced by the mast into the building, and to prevent the building from distorting the mast's radiation pattern. Between the transmitter building and the antenna matching unit next to the mast radiator, there is a feeder: either an underground coaxial cable or an overhead wire 'cage' feeder.At facilities with multiple masts, spacings are typically smaller, in order to fit them into the available space.
At modern transmitters or at low power transmitters situated in very small transmitter buildings the transmitter, matching unit and mast radiator can be very close together and even in the same building. This measure saves on feeders, land area and increases the efficiency of the transmitter, if only one mast radiator is in use.
At most facilities the mast radiator is on a separate base close to the antenna matching unit, but it can be sometimes set up the roof of it. This is for example the case at the main transmission mast of the Mühlacker radio transmitter and the main transmission mast of the Ismaning radio transmitter.
For a good groundwave propagation, mast radiators should be built always on a large flat area with good ground conductivity and if possible without inclination. The construction of a mast radiator on the top of a building or a tower, whose height is in the same magnitude range as the wavelengths being transmitted gives a bad groundwave propagation. So mast radiators are (in contrast to FM broadcasting antennas) normally not installed on the top of buildings or towers. Nevertheless in rare cases mast radiators for low power transmissions are installed on top of buildings. So some lighthouses like Reykjanesviti
Reykjanesviti
Reykjanesviti is Iceland's oldest lighthouse. It serves as a landfall light for Reykjavík and Keflavík.- History :The tower is a 31 metres tall construction, situated on the southwestern edge of the Reykjanes peninsula. The original structure was built in 1878; just eight years later the...
carry a mast radiator for a longwave radio beacon on its roof. Also low-power broadcasting stations uses and used such arrangements. The best-known are WGSO in New Orleans and KSBN (AM) on the Delaney Building
Delaney Building
Delaney Building is an 8 floor high rise building in Riverside Avenue in Spokane, Washington. Delaney Building has on its top a 57.9 meters tall free-standing lattice tower insulated against ground, which is used for broadcasting the program of KSBN on 1230 kHz with 250 watts output power...
in Spokane
Spokane
Spokane is a city in the U.S. state of Washington.Spokane may also refer to:*Spokane *Spokane River*Spokane, Missouri*Spokane Valley, Washington*Spokane County, Washington*Spokane-Coeur d'Alene-Paloos War*Spokane * USS Spokane...
. In Europe the low-power broadcasting station at Campobasso uses a mast radiator on a castle.
Fencing
Mast radiators, as with all other equipment showing over 42 volts on exposed components within 4 metres of the ground, are required to be fenced in. Sometimes wooden fences are used in order to prevent signal interference, which could occur due to currents induced by radio signals in metallic fences.If the mast radiator is mounted on the top of the helix building, which must be over four metres in height; or the mast is grounded, with the feed being located not less than four metres above the ground, a fence is not required.
Nevertheless it is always recommended to fence in any mast radiator in order to prevent unauthorized climbing.
Ancillary connections
A mast radiator may need various electrical connections other than the transmitter feed lineFeed line
In a radio antenna, the feed line is the cable or other transmission line that connects the antenna with the radio transmitter or receiver. In a transmitter, it feeds the radio frequency current from the transmitter to the antenna, where it is radiated as radio waves. In a receiver it transfers...
. Such connections include static drain chokes for lightning protection, power supplies for aircraft warning lamps
Aircraft warning lights
Aircraft warning lights are high-intensity lighting devices that are attached to tall structures and are used as collision avoidance measures. Such devices make structures more visible to passing aircraft and are usually used at night, although they may be used during the day as well...
, and coaxial feeders for ancillary antennas mounted on the mast. A variety of techniques is used to 'isolate' these connections from the high RF
Radio frequency
Radio frequency is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals...
voltage on the mast, such as chokes
Choke (electronics)
A choke is a coil of insulated wire, often wound on a magnetic core, used as a passive inductor which blocks higher-frequency alternating current in an electrical circuit while passing signals of much lower frequency and direct current by having an impedance largely determined by reactance, which...
, parallel tuned circuits and coupling loops, on a base-fed mast. On a shunt-fed mast, where the base is grounded, no such measures are necessary.
Anti-fading aerials
An anti-fading aerial is a transmission aerial for long- and mediumwave with a flat vertical radiation pattern, in order to push the mush zoneMush zone
In mediumwave broadcasting, a mush zone is a region where the ground wave and sky wave from a transmitter are received at approximately equal signal strength, resulting in interference between the two, which will typically cause fading and distorted audio....
far away from the transmitter site. An anti-fading aerial must reduce radiation at elevations of more than 50 degrees as much as possible.
In its simplest form it is an aerial of half wavelength. Such an aerial should be as thin as possible. In early days therefore a wire was hung up in a wood framework tower. Nowadays a radio mast is therefore used, which is fed at its foot and in a certain height. Therefore the radio mast must be insulated against ground and be divided by a separation insulator electrically in two parts, where for feeding of the upper part either a cable inside the mast construction or the ladder, which must be mounted insulated is used. The medium wave transmitters Mühlacker
Transmitter Muehlacker
The Mühlacker Broadcasting Transmission Facility is a radio transmission facility near Mühlacker, Germany, first put into service in 1930. It uses two guyed steel tube masts as aerials and one guyed steel framework mast, which are insulated against ground. It has two transmission aerials for...
, Wolfsheim
Rheinsender
The Rheinsender is a large medium-wave transmission facility near Wolfsheim, southwest of Mainz for the frequency 1017 kHz. The Rhine transmitter was established in 1950 and went on the air May 15, 1950. It belongs to SWR and transmitted until the middle of the 1990s with 600 kilowatts...
and Hamburg
Transmitter Hamburg-Billstedt
The Transmitter Hamburg-Billstedt is a broadcasting facility in Hamburg-Billstedt, established in 1934. It is owned and operated by the Norddeutscher Rundfunk public broadcasting service, but open to competitors, too....
use such aerials. There are also radio masts for fading reducing aerials with two separation insulators as at Ismaning
Transmitter Ismaning
The Transmitter Ismaning was a large radio station inaugurated in 1932. From 1932 to 1934 this transmitter, which replaced the transmitter in Munich-Stadelheim, used a T-antenna as transmitting antenna, which was hung up two 115-meter-high freestanding wood framework towers...
.
Because such separation insulators are more sensitive as the whole other construction of the radio mast, bigger horizontal forces, which could be generated by wind caused oscillations, should be inhibited. Therefore some radio mast with built in separation insulators have oscillation dampers just above the separation insulator. You find such device at the radio masts of the transmitters Wolfsheim
Rheinsender
The Rheinsender is a large medium-wave transmission facility near Wolfsheim, southwest of Mainz for the frequency 1017 kHz. The Rhine transmitter was established in 1950 and went on the air May 15, 1950. It belongs to SWR and transmitted until the middle of the 1990s with 600 kilowatts...
, Hamburg
Transmitter Hamburg-Billstedt
The Transmitter Hamburg-Billstedt is a broadcasting facility in Hamburg-Billstedt, established in 1934. It is owned and operated by the Norddeutscher Rundfunk public broadcasting service, but open to competitors, too....
and Ismaning
Transmitter Ismaning
The Transmitter Ismaning was a large radio station inaugurated in 1932. From 1932 to 1934 this transmitter, which replaced the transmitter in Munich-Stadelheim, used a T-antenna as transmitting antenna, which was hung up two 115-meter-high freestanding wood framework towers...
.
Another possibility for reducing an anti-fading aerial is the usage of dipoles hung up in a certain height above ground. A further possibility of the realization an anti-fading aerial is a circle group aerial. Therefore many mast radiators were arranged on a circle and fed in equal phase. With such facilities very flat radiation patterns could be realized, although they are very expensive, because multiple radio masts are required. Taldom transmitter
Taldom transmitter
Taldom transmitter is a large facility for longwave and shortwave broadcasting near Taldom, Russia. It transmits on two longwave frequencies, on 153 kHz with 300 kW and on 261 kHz with a power of 2,500 kW. Latter is the most powerful broadcasting station in the world...
and Tulagino transmitter in Russia are obviously the only radio stations using such an antenna. In earlier days longwave transmitter Orlunda
Longwave transmitter Orlunda
The Orlunda longwave transmitter was a longwave broadcast facility in central Sweden which broadcast Sveriges Radio Programme 1 from 1962 to 1991...
in Sweden also used such an antenna.
Records
The tallest mast radiator ever built was the Warsaw Radio MastWarsaw radio mast
The Warsaw radio mast was the world's tallest structure until its collapse on 8 August 1991. It is the second tallest land-based structure ever built, being surpassed as tallest by the Burj Khalifa, completed in 2010....
at Konstantynow, Poland. It was 646.38 metres high but collapsed in 1991. Currently the masts of the Lualualei VLF transmitter, at 458.11 metres, are the tallest mast radiators insulated against ground. In contrast to the Warsaw Radio Mast, the Lualualei antenna uses extensive electrical lengthening
Electrical lengthening
Electrical lengthening is the modification of an aerial which is shorter than a whole-number multiple of a quarter of the radiated wavelength, by means of a suitable electronic device, without changing the physical length of the aerial, in such a way that it corresponds electrically to the next...
measures. The tallest mast radiator not using electrical lengthening may be the Hellissandur longwave radio mast
Longwave radio mast Hellissandur
The Longwave radio mast Hellissandur is a 412 metre high guyed radio mast for longwave transmissions at Gufuskálar in the vicinity of Hellissandur on the peninsula Snæfellsnes of Iceland. This mast, which is the tallest structure in Western Europe, is insulated against ground and guyed in 5 levels...
. It is 411.48 metres high.