A mast radiator (or 'radiating tower') is a radio mast or belfry in which the accomplished anatomy itself functions as an antenna. This architecture is frequently acclimated for transmitting antennas operating at low frequencies, in the VLF, LF and MF ranges, in accurate those acclimated for AM broadcasting. The metal mast is electrically affiliated to the transmitter. Its abject is usually army on a nonconductive abutment to insulate it from the ground. A mast radiator is a anatomy of monopole antenna.
Tuesday, February 14, 2012
Design considerations
Design
Most mast radiators are congenital as guyed masts cloistral from the arena at the base. Steel filigree masts, of triangular cross-section, are the a lot of accepted type. Aboveboard filigree masts and tubular masts are aswell sometimes used. To ensure that the belfry is a connected conductor, the tower's structural sections are electrically affirmed at the joints by abbreviate chestnut jumpers which are anchored to anniversary side.
At its base, the mast is usually army on a blubbery bowl insulator, which has the compressive backbone to abutment the tower's weight and the dielectric backbone to bear the top RF voltage activated by the transmitter. The RF ability to drive the antenna is supplied by an antenna tuner unit, usually housed in a baby architecture alleged a braid architecture next to the mast, and the cable bartering the accepted is artlessly anchored to the tower. The absolute transmitter is usually amid in a abstracted building, which food RF ability to the braid architecture via a manual line
Free-standing building are aswell acclimated as beaming structures. These building can accept a triangular or a aboveboard cantankerous section. One of the best-known beaming building is the Blosenbergturm in Beromünster, Switzerland. Masts of bottle fibre are sometimes acclimated for some baby constructions.
Most mast radiators are congenital as guyed masts cloistral from the arena at the base. Steel filigree masts, of triangular cross-section, are the a lot of accepted type. Aboveboard filigree masts and tubular masts are aswell sometimes used. To ensure that the belfry is a connected conductor, the tower's structural sections are electrically affirmed at the joints by abbreviate chestnut jumpers which are anchored to anniversary side.
At its base, the mast is usually army on a blubbery bowl insulator, which has the compressive backbone to abutment the tower's weight and the dielectric backbone to bear the top RF voltage activated by the transmitter. The RF ability to drive the antenna is supplied by an antenna tuner unit, usually housed in a baby architecture alleged a braid architecture next to the mast, and the cable bartering the accepted is artlessly anchored to the tower. The absolute transmitter is usually amid in a abstracted building, which food RF ability to the braid architecture via a manual line
Free-standing building are aswell acclimated as beaming structures. These building can accept a triangular or a aboveboard cantankerous section. One of the best-known beaming building is the Blosenbergturm in Beromünster, Switzerland. Masts of bottle fibre are sometimes acclimated for some baby constructions.
Mast height
The ideal acme of a mast radiator depends on manual frequency, demographics for the location, and terrain. For radio systems in the longwave and mediumwave ambit the amount of the acme should be in the ambit amid one sixth and 5 eighths of the wavelength, with favourite ethics at the division or the bisected of the broadcast wavelength. When this is not consistently possible, masts with a loading coil, 'capacity hat' or agnate loading adjustment are used. The quarter-wave mast is a anatomy of monopole antenna.
The acme of the mast determines the radiation properties. For top ability transmitters in the MW range, masts with heights about bisected of the broadcast amicableness are adopted because they focus the broadcast ability bigger to the arena than structures with heights of division wavelengths, which are adopted for economical affidavit for low ability average beachcomber transmitters. A focus of broadcast ability appear the arena is abundant adapted on frequencies beneath 3 megahertz, because groundwave advancement is actual stable. Masts best than 5 eighths of the amicableness are commonly not used, because they appearance bad vertical radiation patterns, so masts for mediumwave transmitters do not commonly beat 300 metres. For longwave transmitters, however, the architecture of masts with heights of half-wave amicableness is, because of economical affidavit (and conceivably problems with the flight safety), in a lot of cases impossible. The alone so far accomplished radio mast for longwave with a acme of the bisected breadth of the broadcast amicableness was the Warszawa Radio Mast at Konstantynów, Poland. At the time of its collapse in 1991 it was the tallest manmade anatomy in the world, at 646.38 metres (2,120.67 ft) tall. For frequencies beneath longwave masts are electrically continued by loading coils or accommodation hats on the top, because masts of even division beachcomber breadth would be too high.
edit Feed arrangements
There are three means of agriculture a mast radiator from a transmitter:
Base feed: the mast is accurate on an insulator, and the transmitter is affiliated to the mast just aloft it;
Shunt feed: the mast is ashore and the transmitter feeds it via a wire affiliated to the mast allotment way up. (This is a agnate approach, on a beyond scale, to the 'gamma match' accepted a part of abecedarian radio operators for VHF and UHF abecedarian radio antennas.)
Multiple feed: the anatomy is disconnected into two (or more) sections with insulators between, anniversary apart fed. This beeline adjustment enhances low-angle (ground wave) radiation and reduces high-angle (sky wave) radiation. This increases the ambit to the concoction area area the arena beachcomber and sky beachcomber are at agnate backbone at night. This blazon of antenna is accepted as an anti-fading aeriform (see below).
There is usually an antenna analogous assemblage to bout the impedance of the transmitter or agriculturalist to the antenna. Depending on the ability involved, this may be a baby box or a hut or building. It will about accommodate an L-network to transform the modulus of impedance, and a braid or capacitor in alternation with the mast affiliation to 'tune out' any acknowledging component.
The acme of the mast determines the radiation properties. For top ability transmitters in the MW range, masts with heights about bisected of the broadcast amicableness are adopted because they focus the broadcast ability bigger to the arena than structures with heights of division wavelengths, which are adopted for economical affidavit for low ability average beachcomber transmitters. A focus of broadcast ability appear the arena is abundant adapted on frequencies beneath 3 megahertz, because groundwave advancement is actual stable. Masts best than 5 eighths of the amicableness are commonly not used, because they appearance bad vertical radiation patterns, so masts for mediumwave transmitters do not commonly beat 300 metres. For longwave transmitters, however, the architecture of masts with heights of half-wave amicableness is, because of economical affidavit (and conceivably problems with the flight safety), in a lot of cases impossible. The alone so far accomplished radio mast for longwave with a acme of the bisected breadth of the broadcast amicableness was the Warszawa Radio Mast at Konstantynów, Poland. At the time of its collapse in 1991 it was the tallest manmade anatomy in the world, at 646.38 metres (2,120.67 ft) tall. For frequencies beneath longwave masts are electrically continued by loading coils or accommodation hats on the top, because masts of even division beachcomber breadth would be too high.
edit Feed arrangements
There are three means of agriculture a mast radiator from a transmitter:
Base feed: the mast is accurate on an insulator, and the transmitter is affiliated to the mast just aloft it;
Shunt feed: the mast is ashore and the transmitter feeds it via a wire affiliated to the mast allotment way up. (This is a agnate approach, on a beyond scale, to the 'gamma match' accepted a part of abecedarian radio operators for VHF and UHF abecedarian radio antennas.)
Multiple feed: the anatomy is disconnected into two (or more) sections with insulators between, anniversary apart fed. This beeline adjustment enhances low-angle (ground wave) radiation and reduces high-angle (sky wave) radiation. This increases the ambit to the concoction area area the arena beachcomber and sky beachcomber are at agnate backbone at night. This blazon of antenna is accepted as an anti-fading aeriform (see below).
There is usually an antenna analogous assemblage to bout the impedance of the transmitter or agriculturalist to the antenna. Depending on the ability involved, this may be a baby box or a hut or building. It will about accommodate an L-network to transform the modulus of impedance, and a braid or capacitor in alternation with the mast affiliation to 'tune out' any acknowledging component.
Location on transmission facility
At some facilities, abnormally the earlier and higher-powered installations, the mast radiator may be amid at some ambit of the transmitter building, in adjustment to abate the acreage backbone induced by the mast into the building, and to anticipate the architecture from distorting the mast's radiation pattern. Between the transmitter architecture and the antenna analogous assemblage next to the mast radiator, there is a feeder: either an underground coaxial cable or an aerial wire 'cage' feeder.
At accessories with assorted masts, spacings are about smaller, in adjustment to fit them into the accessible space.
At avant-garde transmitters or at low ability transmitters anchored in actual baby transmitter barrio the transmitter, analogous assemblage and mast radiator can be actual abutting calm and even in the aforementioned building. This admeasurement saves on feeders, acreage breadth and increases the ability of the transmitter, if alone one mast radiator is in use.
At a lot of accessories the mast radiator is on a abstracted abject abutting to the antenna analogous unit, but it can be sometimes set up the roof of it. This is for archetype the case at the capital manual mast of the Mühlacker radio transmitter and the capital manual mast of the Ismaning radio transmitter.
For a acceptable groundwave propagation, mast radiators should be congenital consistently on a ample collapsed breadth with acceptable arena application and if accessible after inclination. The architecture of a mast radiator on the top of a architecture or a tower, whose acme is in the aforementioned consequence ambit as the wavelengths getting transmitted gives a bad groundwave propagation. So mast radiators are (in adverse to FM broadcasting antennas) commonly not installed on the top of barrio or towers. Nevertheless in attenuate cases mast radiators for low ability transmissions are installed on top of buildings. So some lighthouses like Reykjanesviti backpack a mast radiator for a longwave radio alarm on its roof. Also low-power broadcasting stations uses and acclimated such arrangements. The best-known are WGSO in New Orleans and KSBN (AM) on the Delaney Architecture in Spokane. In Europe the low-power broadcasting base at Campobasso uses a mast radiator on a castle.
At accessories with assorted masts, spacings are about smaller, in adjustment to fit them into the accessible space.
At avant-garde transmitters or at low ability transmitters anchored in actual baby transmitter barrio the transmitter, analogous assemblage and mast radiator can be actual abutting calm and even in the aforementioned building. This admeasurement saves on feeders, acreage breadth and increases the ability of the transmitter, if alone one mast radiator is in use.
At a lot of accessories the mast radiator is on a abstracted abject abutting to the antenna analogous unit, but it can be sometimes set up the roof of it. This is for archetype the case at the capital manual mast of the Mühlacker radio transmitter and the capital manual mast of the Ismaning radio transmitter.
For a acceptable groundwave propagation, mast radiators should be congenital consistently on a ample collapsed breadth with acceptable arena application and if accessible after inclination. The architecture of a mast radiator on the top of a architecture or a tower, whose acme is in the aforementioned consequence ambit as the wavelengths getting transmitted gives a bad groundwave propagation. So mast radiators are (in adverse to FM broadcasting antennas) commonly not installed on the top of barrio or towers. Nevertheless in attenuate cases mast radiators for low ability transmissions are installed on top of buildings. So some lighthouses like Reykjanesviti backpack a mast radiator for a longwave radio alarm on its roof. Also low-power broadcasting stations uses and acclimated such arrangements. The best-known are WGSO in New Orleans and KSBN (AM) on the Delaney Architecture in Spokane. In Europe the low-power broadcasting base at Campobasso uses a mast radiator on a castle.
Fencing
Mast radiators, as with all added accessories assuming over 42 volts on apparent apparatus aural 4 metres of the ground,where? are appropriate to be belted in. Sometimes board fences are acclimated in adjustment to anticipate arresting interference, which could action due to currents induced by radio signals in brownish fences. If the mast radiator is army on the top of the braid building, which have to be over four metres in height; or the mast is grounded, with the augment getting amid not beneath than four metres aloft the ground, a fence is not required. Nevertheless it is consistently recommended to fence in any mast radiator in adjustment to anticipate crooked climbing.
edit Accessory connections
A mast radiator may charge assorted electrical access added than the transmitter augment line. Such access cover changeless cesspool chokes for lightning protection, ability food for aircraft admonishing lamps, and coaxial feeders for accessory antennas army on the mast. A array of techniques is acclimated to 'isolate' these access from the top RF voltage on the mast, such as chokes, alongside acquainted circuits and coupling loops, on a base-fed mast. On a shunt-fed mast, area the abject is grounded, no such measures are necessary.
edit Accessory connections
A mast radiator may charge assorted electrical access added than the transmitter augment line. Such access cover changeless cesspool chokes for lightning protection, ability food for aircraft admonishing lamps, and coaxial feeders for accessory antennas army on the mast. A array of techniques is acclimated to 'isolate' these access from the top RF voltage on the mast, such as chokes, alongside acquainted circuits and coupling loops, on a base-fed mast. On a shunt-fed mast, area the abject is grounded, no such measures are necessary.
Anti-fading aerials
An anti-fading aeriform is a manual aeriform for long- and mediumwave with a burst vertical radiation pattern, in adjustment to advance the concoction area far abroad from the transmitter site. An anti-fading aeriform accept to abate radiation at elevations of added than 50 degrees as abundant as possible.
In its simplest anatomy it is an aeriform of bisected wavelength. Such an aeriform should be as attenuate as possible. In aboriginal canicule accordingly a wire was afraid up in a copse framework tower. Nowadays a radio mast is accordingly used, which is fed at its bottom and in a assertive height. Accordingly the radio mast accept to be cloistral adjoin arena and be disconnected by a break insulator electrically in two parts, area for agriculture of the top allotment either a cable central the mast architecture or the ladder, which accept to be army cloistral is used. The average beachcomber transmitters Mühlacker, Wolfsheim and Hamburg use such aerials. There are aswell radio masts for crumbling abbreviation aerials with two break insulators as at Ismaning.
Because such break insulators are added acute as the accomplished added architecture of the radio mast, bigger accumbent forces, which could be generated by wind acquired oscillations, should be inhibited. Accordingly some radio mast with congenital break insulators accept cadence dampers just aloft the break insulator. You acquisition such accessory at the radio masts of the transmitters Wolfsheim, Hamburg and Ismaning.
Another achievability for abbreviation an anti-fading aeriform is the acceptance of dipoles afraid up in a assertive acme aloft ground. A added achievability of the ability an anti-fading aeriform is a amphitheater accumulation aerial. Accordingly abounding mast radiators were abiding on a amphitheater and fed in according phase. With such accessories actual burst radiation patterns could be realized, although they are actual expensive, because assorted radio masts are required. Taldom transmitter and Tulagino transmitter in Russia are acutely the alone radio stations application such an antenna. In beforehand canicule longwave transmitter Orlunda in Sweden aswell acclimated such an antenna.
edit Records
The tallest mast radiator anytime congenital was the Warsaw Radio Mast at Konstantynow, Poland. It was 646.38 metres top but burst in 1991. Currently the masts of the Lualualei VLF transmitter, at 458.11 metres, are the tallest mast radiators cloistral adjoin ground. In adverse to the Warsaw Radio Mast, the Lualualei antenna uses all-encompassing electrical addition measures. The tallest mast radiator not application electrical addition may be the Hellissandur longwave radio mast. It is 411.48 metres high.
In its simplest anatomy it is an aeriform of bisected wavelength. Such an aeriform should be as attenuate as possible. In aboriginal canicule accordingly a wire was afraid up in a copse framework tower. Nowadays a radio mast is accordingly used, which is fed at its bottom and in a assertive height. Accordingly the radio mast accept to be cloistral adjoin arena and be disconnected by a break insulator electrically in two parts, area for agriculture of the top allotment either a cable central the mast architecture or the ladder, which accept to be army cloistral is used. The average beachcomber transmitters Mühlacker, Wolfsheim and Hamburg use such aerials. There are aswell radio masts for crumbling abbreviation aerials with two break insulators as at Ismaning.
Because such break insulators are added acute as the accomplished added architecture of the radio mast, bigger accumbent forces, which could be generated by wind acquired oscillations, should be inhibited. Accordingly some radio mast with congenital break insulators accept cadence dampers just aloft the break insulator. You acquisition such accessory at the radio masts of the transmitters Wolfsheim, Hamburg and Ismaning.
Another achievability for abbreviation an anti-fading aeriform is the acceptance of dipoles afraid up in a assertive acme aloft ground. A added achievability of the ability an anti-fading aeriform is a amphitheater accumulation aerial. Accordingly abounding mast radiators were abiding on a amphitheater and fed in according phase. With such accessories actual burst radiation patterns could be realized, although they are actual expensive, because assorted radio masts are required. Taldom transmitter and Tulagino transmitter in Russia are acutely the alone radio stations application such an antenna. In beforehand canicule longwave transmitter Orlunda in Sweden aswell acclimated such an antenna.
edit Records
The tallest mast radiator anytime congenital was the Warsaw Radio Mast at Konstantynow, Poland. It was 646.38 metres top but burst in 1991. Currently the masts of the Lualualei VLF transmitter, at 458.11 metres, are the tallest mast radiators cloistral adjoin ground. In adverse to the Warsaw Radio Mast, the Lualualei antenna uses all-encompassing electrical addition measures. The tallest mast radiator not application electrical addition may be the Hellissandur longwave radio mast. It is 411.48 metres high.
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