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.
131-498: Tokyo Tower ( 東京タワー , Tōkyō Tawā , pronounced [toːkʲoː taɰᵝaː] ) , officially Japan Radio Tower ( 日本電波塔 , Nippon denpatō ) is a communications and observation tower in the district of Shiba-koen in Minato, Tokyo , Japan, completed in 1958. At 332.9 meters (1,092 ft), it was the tallest tower in Japan until the construction of Tokyo Skytree in 2012. It
262-526: A FamilyMart convenience store and a souvenir shop. This floor's main attractions, however, are the three elevators that serve as a direct ride to the Main Observatory. The second floor is primarily a food and shopping area. In addition to the five standalone restaurants, the second floor's food court consists of four restaurants, including a McDonald's and a Pizza-La . FootTown's third and fourth floors house several tourist attractions. The third floor
393-569: A kite can serve as a temporary support. It can carry an antenna or a wire (for VLF, LW or MW) up to an appropriate height. Such an arrangement is used occasionally by military agencies or radio amateurs. The American broadcasters TV Martí broadcast a television program to Cuba by means of such a balloon. In 2013, interest began in using unmanned aerial vehicles (drones) for telecom purposes. For two VLF transmitters wire antennas spun across deep valleys are used. The wires are supported by small masts or towers or rock anchors. The same technique
524-427: A tower is a self-supporting or cantilevered structure, while a mast is held up by stays or guy-wires . There are a few borderline designs that are partly free-standing and partly guyed, called additionally guyed towers . Examples: The first experiments in radio communication were conducted by Guglielmo Marconi beginning in 1894. In 1895–1896 he invented the vertical monopole or Marconi antenna , which
655-412: A BOS process is manufactured in one-twelfth the time. Today, electric arc furnaces (EAF) are a common method of reprocessing scrap metal to create new steel. They can also be used for converting pig iron to steel, but they use a lot of electrical energy (about 440 kWh per metric ton), and are thus generally only economical when there is a plentiful supply of cheap electricity. The steel industry
786-464: A capacitive top-load. In a second paper the same year he showed that the amount of power radiated horizontally in ground waves reached a maximum at a mast height of 5 / 8 wavelength . By 1930 the expense of the T-antenna led broadcasters to adopt the mast radiator antenna, in which the metal structure of the mast itself functions as the antenna. One of the first types used
917-684: A carbon-intermediate steel by the 1st century AD. There is evidence that carbon steel was made in Western Tanzania by the ancestors of the Haya people as early as 2,000 years ago by a complex process of "pre-heating" allowing temperatures inside a furnace to reach 1300 to 1400 °C. Evidence of the earliest production of high carbon steel in South Asia is found in Kodumanal in Tamil Nadu ,
1048-444: A change of volume. In this case, expansion occurs. Internal stresses from this expansion generally take the form of compression on the crystals of martensite and tension on the remaining ferrite, with a fair amount of shear on both constituents. If quenching is done improperly, the internal stresses can cause a part to shatter as it cools. At the very least, they cause internal work hardening and other microscopic imperfections. It
1179-428: A ferrite BCC crystal form, but at higher carbon content it takes a body-centred tetragonal (BCT) structure. There is no thermal activation energy for the transformation from austenite to martensite. There is no compositional change so the atoms generally retain their same neighbours. Martensite has a lower density (it expands during the cooling) than does austenite, so that the transformation between them results in
1310-478: A fraction of the weight (70% less ) which has allowed monopoles and towers to be built in locations that were too expensive or difficult to access with the heavy lifting equipment that is needed for a steel structure. Overall a carbon fiber structure is 40 - 50% faster to be erected compared to traditional building materials. As of 2022 , wood, previously an uncommon material for telecommunications tower construction, has started to become increasingly common. In 2022,
1441-624: A guyed radio mast is installed. One example is the Gerbrandy Tower in Lopik , Netherlands. Further towers of this building method can be found near Smilde , Netherlands and the Fernsehturm in Waldenburg , Germany. Radio, television and cell towers have been documented to pose a hazard to birds. Reports have been issued documenting known bird fatalities and calling for research to find ways to minimize
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#17328561593271572-445: A hard but brittle martensitic structure. The steel is then tempered, which is just a specialized type of annealing, to reduce brittleness. In this application the annealing (tempering) process transforms some of the martensite into cementite, or spheroidite and hence it reduces the internal stresses and defects. The result is a more ductile and fracture-resistant steel. When iron is smelted from its ore, it contains more carbon than
1703-466: A member of the World Federation of Great Towers, has been used by many organizations for broadcasting purposes. The structure was intended for broadcasting television, but radio antennas were installed in 1961 because it could accommodate them. While analog and digital television broadcasts are no longer conducted from the site, two FM radio stations remain on Tokyo Tower. Stations that use or have used
1834-412: A narrow range of concentrations of mixtures of carbon and iron that make steel, several different metallurgical structures, with very different properties can form. Understanding such properties is essential to making quality steel. At room temperature , the most stable form of pure iron is the body-centred cubic (BCC) structure called alpha iron or α-iron. It is a fairly soft metal that can dissolve only
1965-399: A new night-time illumination scheme—titled the "Diamond Veil"—to celebrate the tower's 50th anniversary. The arrangement featured 276 lights in seven colors equally distributed across the towers four faces. When employing specialty lighting on the tower, the Main Observatory often plays an important role. During the second international " White Band Day" on 10 September 2005,
2096-421: A radio and television broadcasting antenna support structure and is a tourist destination that houses several different attractions. The tower recorded its 190 millionth visitor in 2024. Visitor numbers had been steadily declining, bottoming out at 2.3 million in 2000 before rising since then. The first area tourists visit upon reaching the tower is FootTown, a four-story building stationed directly under
2227-534: A small concentration of carbon, no more than 0.005% at 0 °C (32 °F) and 0.021 wt% at 723 °C (1,333 °F). The inclusion of carbon in alpha iron is called ferrite . At 910 °C, pure iron transforms into a face-centred cubic (FCC) structure, called gamma iron or γ-iron. The inclusion of carbon in gamma iron is called austenite. The more open FCC structure of austenite can dissolve considerably more carbon, as much as 2.1%, (38 times that of ferrite) carbon at 1,148 °C (2,098 °F), which reflects
2358-448: A steel's final rolling, it is heat treated for strength; however, this is relatively rare. Steel was known in antiquity and was produced in bloomeries and crucibles . The earliest known production of steel is seen in pieces of ironware excavated from an archaeological site in Anatolia ( Kaman-Kalehöyük ) which are nearly 4,000 years old, dating from 1800 BC. Wootz steel
2489-403: A tower doubling as a flagpole attracted controversy in 2004 in relation to the U.S. presidential campaign of that year , and highlighted the sentiment that such disguises serve more to allow the installation of such towers in subterfuge, away from public scrutiny, rather than to serve towards the beautification of the landscape. A mast radiator or mast antenna is a radio tower or mast in which
2620-575: A tower, the structure may be parallel-sided or taper over part or all of its height. When constructed of several sections which taper exponentially with height, in the manner of the Eiffel Tower , the tower is said to be an Eiffelized one. The Crystal Palace tower in London is an example. Guyed masts are sometimes also constructed out of steel tubes. This construction type has the advantage that cables and other components can be protected from weather inside
2751-484: A wood telecommunications tower – the first of its kind in Italy – replaced a previously-existing steel structure to blend in with its wooded surroundings. One of the most commonly cited reasons telecom companies opt for wood is because it is the only material in the industry that is climate positive . For this reason, some utility pole distributors started to offer wood towers to meet the growing demands of 5G infrastructure. In
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#17328561593272882-672: Is continuously cast into long slabs, cut and shaped into bars and extrusions and heat treated to produce a final product. Today, approximately 96% of steel is continuously cast, while only 4% is produced as ingots. The ingots are then heated in a soaking pit and hot rolled into slabs, billets , or blooms . Slabs are hot or cold rolled into sheet metal or plates. Billets are hot or cold rolled into bars, rods, and wire. Blooms are hot or cold rolled into structural steel , such as I-beams and rails . In modern steel mills these processes often occur in one assembly line , with ore coming in and finished steel products coming out. Sometimes after
3013-461: Is a lattice tower inspired by the Eiffel Tower , and is painted white and international orange to comply with air safety regulations. The tower's main sources of income are tourism and antenna leasing. FootTown, a four-story building directly under the tower, houses museums, restaurants, and shops. Departing from there, guests can visit two observation decks. The two-story Main Deck (formerly known as
3144-403: Is common for quench cracks to form when steel is water quenched, although they may not always be visible. There are many types of heat treating processes available to steel. The most common are annealing , quenching , and tempering . Annealing is the process of heating the steel to a sufficiently high temperature to relieve local internal stresses. It does not create a general softening of
3275-453: Is currently the tallest guyed tubular mast in the world after the Belmont transmitting station was reduced in height in 2010. Reinforced concrete towers are relatively expensive to build but provide a high degree of mechanical rigidity in strong winds. This can be important when antennas with narrow beamwidths are used, such as those used for microwave point-to-point links, and when the structure
3406-403: Is desirable. To become steel, it must be reprocessed to reduce the carbon to the correct amount, at which point other elements can be added. In the past, steel facilities would cast the raw steel product into ingots which would be stored until use in further refinement processes that resulted in the finished product. In modern facilities, the initial product is close to the final composition and
3537-449: Is distinguishable from wrought iron (now largely obsolete), which may contain a small amount of carbon but large amounts of slag . Iron is commonly found in the Earth's crust in the form of an ore , usually an iron oxide, such as magnetite or hematite . Iron is extracted from iron ore by removing the oxygen through its combination with a preferred chemical partner such as carbon which
3668-461: Is frequently used in the Japanese kaiju (giant monster) film genre. It has been the location of numerous battles and visitations by Godzilla , Mothra , Gamera and King Kong ( King Kong Escapes ) wherein it is frequently destroyed and rebuilt. Based on the popular manga series by Ryōhei Saigan, the 2005 film Always Sanchōme no Yūhi was a nostalgic view of life in the neighborhoods beneath
3799-408: Is heat treated to contain both a ferritic and martensitic microstructure to produce a formable, high strength steel. Transformation Induced Plasticity (TRIP) steel involves special alloying and heat treatments to stabilize amounts of austenite at room temperature in normally austenite-free low-alloy ferritic steels. By applying strain, the austenite undergoes a phase transition to martensite without
3930-623: Is home to the Guinness World Records Museum Tokyo, a museum that houses life-size figures, photo panels and memorabilia depicting interesting records that have been authenticated by the Guinness Book. The Tokyo Tower Wax Museum, opened in 1970, displayed wax figures imported from London where they were made until it was closed in 2013. The figures on display range from pop culture icons such as The Beatles to religious figures such as Jesus Christ . A hologram gallery named
4061-535: Is known as stainless steel . Tungsten slows the formation of cementite , keeping carbon in the iron matrix and allowing martensite to preferentially form at slower quench rates, resulting in high-speed steel . The addition of lead and sulphur decrease grain size, thereby making the steel easier to turn , but also more brittle and prone to corrosion. Such alloys are nevertheless frequently used for components such as nuts, bolts, and washers in applications where toughness and corrosion resistance are not paramount. For
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4192-578: Is not an essential feature. A special form of the radio tower is the telescopic mast . These can be erected very quickly. Telescopic masts are used predominantly in setting up temporary radio links for reporting on major news events, and for temporary communications in emergencies. They are also used in tactical military networks. They can save money by needing to withstand high winds only when raised, and as such are widely used in amateur radio . Telescopic masts consist of two or more concentric sections and come in two principal types: A tethered balloon or
4323-687: Is often considered an indicator of economic progress, because of the critical role played by steel in infrastructural and overall economic development . In 1980, there were more than 500,000 U.S. steelworkers. By 2000, the number of steelworkers had fallen to 224,000. The economic boom in China and India caused a massive increase in the demand for steel. Between 2000 and 2005, world steel demand increased by 6%. Since 2000, several Indian and Chinese steel firms have expanded to meet demand, such as Tata Steel (which bought Corus Group in 2007), Baosteel Group and Shagang Group . As of 2017 , though, ArcelorMittal
4454-507: Is one of the largest manufacturing industries in the world, but also one of the most energy and greenhouse gas emission intense industries, contributing 8% of global emissions. However, steel is also very reusable: it is one of the world's most-recycled materials, with a recycling rate of over 60% globally . The noun steel originates from the Proto-Germanic adjective * * stahliją or * * stakhlijan 'made of steel', which
4585-463: Is one of the most commonly manufactured materials in the world. Steel is used in buildings, as concrete reinforcing rods, in bridges, infrastructure, tools, ships, trains, cars, bicycles, machines, electrical appliances, furniture, and weapons. Iron is always the main element in steel, but many other elements may be present or added. Stainless steels , which are resistant to corrosion and oxidation , typically need an additional 11% chromium . Iron
4716-544: Is one of the world's most-recycled materials, with a recycling rate of over 60% globally; in the United States alone, over 82,000,000 metric tons (81,000,000 long tons; 90,000,000 short tons) were recycled in the year 2008, for an overall recycling rate of 83%. As more steel is produced than is scrapped, the amount of recycled raw materials is about 40% of the total of steel produced - in 2016, 1,628,000,000 tonnes (1.602 × 10 long tons; 1.795 × 10 short tons) of crude steel
4847-510: Is possible only by reducing iron's ductility. Steel was produced in bloomery furnaces for thousands of years, but its large-scale, industrial use began only after more efficient production methods were devised in the 17th century, with the introduction of the blast furnace and production of crucible steel . This was followed by the Bessemer process in England in the mid-19th century, and then by
4978-434: Is possible to make very high-carbon (and other alloy material) steels, but such are not common. Cast iron is not malleable even when hot, but it can be formed by casting as it has a lower melting point than steel and good castability properties. Certain compositions of cast iron, while retaining the economies of melting and casting, can be heat treated after casting to make malleable iron or ductile iron objects. Steel
5109-400: Is quite ductile , or soft and easily formed. In steel, small amounts of carbon, other elements, and inclusions within the iron act as hardening agents that prevent the movement of dislocations . The carbon in typical steel alloys may contribute up to 2.14% of its weight. Varying the amount of carbon and many other alloying elements, as well as controlling their chemical and physical makeup in
5240-457: Is related to * * stahlaz or * * stahliją 'standing firm'. The carbon content of steel is between 0.02% and 2.14% by weight for plain carbon steel ( iron - carbon alloys ). Too little carbon content leaves (pure) iron quite soft, ductile, and weak. Carbon contents higher than those of steel make a brittle alloy commonly called pig iron . Alloy steel is steel to which other alloying elements have been intentionally added to modify
5371-410: Is specially lit for some annual events. Since 2000, the entire tower has been illuminated in a pink light on 1 October to highlight the beginning of National Breast Cancer Awareness Month . The tower has also had a variety of special lighting arrangements for Christmas since 1994. During New Year's Eve , the tower lights up at midnight with a year number displayed on one side of the observatory to mark
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5502-619: Is still in use. Disguised cell sites sometimes can be introduced into environments that require a low-impact visual outcome, by being made to look like trees, chimneys or other common structures. Many people view bare cellphone towers as ugly and an intrusion into their neighbourhoods. Even though people increasingly depend upon cellular communications, they are opposed to the bare towers spoiling otherwise scenic views. Many companies offer to 'hide' cellphone towers in, or as, trees, church towers, flag poles, water tanks and other features. There are many providers that offer these services as part of
5633-441: Is the base metal of steel. Depending on the temperature, it can take two crystalline forms (allotropic forms): body-centred cubic and face-centred cubic . The interaction of the allotropes of iron with the alloying elements, primarily carbon, gives steel and cast iron their range of unique properties. In pure iron, the crystal structure has relatively little resistance to the iron atoms slipping past one another, and so pure iron
5764-489: Is the danger of wind-induced oscillations. This is particularly a concern with steel tube construction. One can reduce this by building cylindrical shock-mounts into the construction. One finds such shock-mounts, which look like cylinders thicker than the mast, for example, at the radio masts of DHO38 in Saterland . There are also constructions, which consist of a free-standing tower, usually from reinforced concrete , onto which
5895-412: Is the most widespread form of construction. It provides great strength, low weight and wind resistance, and economy in the use of materials. Lattices of triangular cross-section are most common, and square lattices are also widely used. Guyed masts are often used; the supporting guy lines carry lateral forces such as wind loads, allowing the mast to be very narrow and simply constructed. When built as
6026-529: Is the world's largest steel producer . In 2005, the British Geological Survey stated China was the top steel producer with about one-third of the world share; Japan , Russia , and the United States were second, third, and fourth, respectively, according to the survey. The large production capacity of steel results also in a significant amount of carbon dioxide emissions inherent related to
6157-498: Is then lost to the atmosphere as carbon dioxide. This process, known as smelting , was first applied to metals with lower melting points, such as tin , which melts at about 250 °C (482 °F), and copper , which melts at about 1,100 °C (2,010 °F), and the combination, bronze, which has a melting point lower than 1,083 °C (1,981 °F). In comparison, cast iron melts at about 1,375 °C (2,507 °F). Small quantities of iron were smelted in ancient times, in
6288-502: Is to be occupied by people. In the 1950s, AT&T built numerous concrete towers, more resembling silos than towers, for its first transcontinental microwave route. In Germany and the Netherlands most towers constructed for point-to-point microwave links are built of reinforced concrete , while in the UK most are lattice towers . Concrete towers can form prestigious landmarks, such as
6419-529: The CN Tower in Toronto , Canada. In addition to accommodating technical staff, these buildings may have public areas such as observation decks or restaurants. The Katanga TV tower near Jabalpur , Madhya Pradesh, in central India hosts a high-power transmitter for the public broadcasters Doordarshan and Prasar Bharati . The Stuttgart TV tower was the first tower in the world to be built in reinforced concrete. It
6550-631: The Golconda area in Andhra Pradesh and Karnataka , regions of India , as well as in Samanalawewa and Dehigaha Alakanda, regions of Sri Lanka . This came to be known as wootz steel , produced in South India by about the sixth century BC and exported globally. The steel technology existed prior to 326 BC in the region as they are mentioned in literature of Sangam Tamil , Arabic, and Latin as
6681-466: The Kantō region on 1 December 2005, each side of the Main Observatory displayed the characters 地デジ ( chi deji , an abbreviation for 地上デジタル放送 chijō dejitaru hōsō terrestrial digital broadcasting). More recently, the observatory displayed both "TOKYO" and "2016" to stress Tokyo's 2016 Olympic bid . Primitive images, such as hearts, have also been displayed using the observatory's windows. Operations at
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#17328561593276812-470: The Tokyo Skytree was opened in 2012. In an attempt to make Tokyo Tower more appealing to NHK and the five other commercial broadcasters who planned to move their transmitting stations to the new tower, Nihon Denpatō officials drafted a plan to extend its digital broadcasting antenna by 80 to 100 meters at a cost of approximately ¥4 billion (US$ 50 million). As a result of their move to
6943-586: The cementation process was described in a treatise published in Prague in 1574 and was in use in Nuremberg from 1601. A similar process for case hardening armour and files was described in a book published in Naples in 1589. The process was introduced to England in about 1614 and used to produce such steel by Sir Basil Brooke at Coalbrookdale during the 1610s. The raw material for this process were bars of iron. During
7074-592: The open-hearth furnace . With the invention of the Bessemer process, a new era of mass-produced steel began. Mild steel replaced wrought iron . The German states were the major steel producers in Europe in the 19th century. American steel production was centred in Pittsburgh , Bethlehem, Pennsylvania , and Cleveland until the late 20th century. Currently, world steel production is centered in China, which produced 54% of
7205-435: The shortwave range, there is little to be gained by raising the antenna more than a half to three quarters of a wavelength above ground level, and at lower frequencies and longer wavelengths, the height becomes infeasibly great (greater than 85 metres (279 ft)). Shortwave transmitters rarely use masts taller than about 100 metres. Because masts, towers and the antennas mounted on them require maintenance, access to
7336-445: The very low frequency band – such long waves that they are nearly unused at present. Because the extreme wavelengths were one to several kilometers long, even the tallest feasible antennas by comparison were still too short, electrically , and consequently had inherently very low radiation resistance (only 5~25 Ohms). In any antenna, low radiation resistance leads to excessive power losses in its surrounding ground system , since
7467-525: The visual horizon . The only way to cover larger areas is to raise the antenna high enough so it has a line-of-sight path to them. Until 8 August 1991, the Warsaw radio mast was the world's tallest supported structure on land; its collapse left the KVLY / KTHI-TV mast as the tallest. There are over 50 radio structures in the United States that are 600 m ( 1 968.5 ft ) or taller. The steel lattice
7598-425: The whole structure is an antenna. Mast antennas are the transmitting antennas typical for long or medium wave broadcasting. Structurally, the only difference is that some mast radiators require the mast base to be insulated from the ground. In the case of an insulated tower, there will usually be one insulator supporting each leg. Some mast antenna designs do not require insulation, however, so base insulation
7729-445: The 17th century, it was realized that the best steel came from oregrounds iron of a region north of Stockholm , Sweden. This was still the usual raw material source in the 19th century, almost as long as the process was used. Crucible steel is steel that has been melted in a crucible rather than having been forged , with the result that it is more homogeneous. Most previous furnaces could not reach high enough temperatures to melt
7860-470: The 17th century, the first step in European steel production has been the smelting of iron ore into pig iron in a blast furnace . Originally employing charcoal, modern methods use coke , which has proven more economical. In these processes, pig iron made from raw iron ore was refined (fined) in a finery forge to produce bar iron , which was then used in steel-making. The production of steel by
7991-540: The 1930s it was found that the diamond shape of the Blaw-Knox tower had an unfavorable current distribution which increased the power emitted at high angles, causing multipath fading in the listening area. By the 1940s the AM broadcast industry had abandoned the Blaw-Knox design for the narrow, uniform cross section lattice mast used today, which had a better radiation pattern. The rise of FM radio and television broadcasting in
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#17328561593278122-476: The 1940s–1950s created a need for even taller masts. The earlier AM broadcasting used LF and MF bands, where radio waves propagate as ground waves which follow the contour of the Earth. The ground-hugging waves allowed the signals to travel beyond the horizon, out to hundreds of kilometers. However the newer FM and TV transmitters used the VHF band, in which radio waves travel by line-of-sight , so they are limited by
8253-619: The 1960s. In Germany the Bielstein transmitter collapsed in 1985. Tubular masts were not built in all countries. In Germany, France, UK, Czech Republic, Slovakia, Japan and the Soviet Union, many tubular guyed masts were built, while there are nearly none in Poland or North America. Several tubular guyed masts were built in cities in Russia and Ukraine. These masts featured horizontal crossbars running from
8384-496: The 40th anniversary of Tokyo Tower. Just as the Eiffel Tower is often used in popular culture to immediately locate a scene in Paris, Tokyo Tower is often used in the same way for Tokyo. It is used in anime and manga such as Doraemon , Tokyo Magnitude 8.0 , Magic Knight Rayearth , Please Save My Earth , Cardcaptor Sakura , Digimon , Detective Conan , Sailor Moon , Tenchi Muyo! and Death Note . The tower
8515-600: The Arabs from Persia, who took it from India. It was originally created from several different materials including various trace elements , apparently ultimately from the writings of Zosimos of Panopolis . In 327 BC, Alexander the Great was rewarded by the defeated King Porus , not with gold or silver but with 30 pounds of steel. A recent study has speculated that carbon nanotubes were included in its structure, which might explain some of its legendary qualities, though, given
8646-495: The Eiffel Tower as it is significantly thinner and simpler in construction. It was opened to the public on 23 December 1958 at a final cost of ¥ 2.8 billion ($ 8.4 million in 1958). Tokyo Tower was mortgaged for ¥10 billion in 2000. It was the tallest artificial structure in Japan until April 2010, when it was surpassed by the Tokyo Skytree . Planned as an antenna for telecommunications and brightly colored in accordance with
8777-570: The Gallery DeLux, a lounge and a few specialty stores are also located on this floor. Tokyo Tower's Trick Art Gallery is located on the building's fourth and final floor. This gallery displays optical illusions , including paintings and objects that visitors can interact with. On the roof of the FootTown building is a small amusement park that contains several small rides and hosts live performances for children. On weekends and holidays, visitors can use
8908-463: The Linz-Donawitz process of basic oxygen steelmaking (BOS), developed in 1952, and other oxygen steel making methods. Basic oxygen steelmaking is superior to previous steelmaking methods because the oxygen pumped into the furnace limited impurities, primarily nitrogen, that previously had entered from the air used, and because, with respect to the open hearth process, the same quantity of steel from
9039-615: The Main Observatory) is at 150 meters (490 ft), while the smaller Top Deck (formerly known as the "Special Observatory") reaches a height of 249.6 meters (819 ft). The names were changed following renovation of the top deck in 2018. The tower is repainted every five years, taking a year to complete the process. In 1961, transmission antennae were added to the tower. They are used for radio and television broadcasting and now broadcast signals for Japanese media outlets such as NHK , TBS Television , and Fuji Television . The height of
9170-631: The Skytree, only one digital television station remained on Tokyo Tower: that of the Open University of Japan , whose JOUD-DTV and JOUD-FM continued on the tower until shutting down in 2018. FM radio stations will continue to use the tower for broadcasting in the Tokyo area. Masahiro Kawada, the tower's planning director, raised the possibility of the tower becoming a backup for the Tokyo Skytree, depending on what
9301-573: The TV broadcasters want or need. The antenna's tip was damaged on 11 March 2011 by the Tōhoku earthquake . On 19 July 2012, Tokyo Tower's height shrank to 315 meters while the top antenna was repaired for damage from the earthquake. Located in the base of the tower is a 4-story building known as FootTown. The first floor includes the Aquarium Gallery, a reception hall, the 400-person-capacity "Tower Restaurant",
9432-613: The Tokyo Tower Top Deck (at the height of 250 m) were suspended in 2016. The Top Deck reopened on March 3, 2018. At that time, Tokyo Tower also announced the renaming of both decks. Renovations on the main deck, which began in September 2016, caused partial closure of the deck. The Tokyo Tower has two mascots named ノッポン Noppon . They are two brothers: Older Brother, who wears blue dungarees , and Younger Brother, who wears red dungarees. They were unveiled on 23 December 1998 to celebrate
9563-418: The United States, for example, wood utility pole distributor Bell Lumber & Pole began developing products for the telecommunications industry . Shorter masts may consist of a self-supporting or guyed wooden pole, similar to a telegraph pole. Sometimes self-supporting tubular galvanized steel poles are used: these may be termed monopoles. In some cases, it is possible to install transmitting antennas on
9694-558: The arrival of the new year. Special Japanese events have been cause to light the tower in several non-traditional ways. In 2002, alternating sections of the tower were lit blue to help celebrate the opening of the FIFA World Cup in Japan. Alternating sections of the tower were lit green on Saint Patrick's Day in 2007 to commemorate the 50th anniversary of Japanese–Irish relations. On a few occasions, Tokyo Tower has even been specially lit to correspond with corporate events. For example,
9825-436: The austenite grain boundaries until the percentage of carbon in the grains has decreased to the eutectoid composition (0.8% carbon), at which point the pearlite structure forms. For steels that have less than 0.8% carbon (hypoeutectoid), ferrite will first form within the grains until the remaining composition rises to 0.8% of carbon, at which point the pearlite structure will form. No large inclusions of cementite will form at
9956-471: The austenite is for it to precipitate out of solution as cementite , leaving behind a surrounding phase of BCC iron called ferrite with a small percentage of carbon in solution. The two, cementite and ferrite, precipitate simultaneously producing a layered structure called pearlite , named for its resemblance to mother of pearl . In a hypereutectoid composition (greater than 0.8% carbon), the carbon will first precipitate out as large inclusions of cementite at
10087-494: The boundaries in hypoeutectoid steel. The above assumes that the cooling process is very slow, allowing enough time for the carbon to migrate. As the rate of cooling is increased the carbon will have less time to migrate to form carbide at the grain boundaries but will have increasingly large amounts of pearlite of a finer and finer structure within the grains; hence the carbide is more widely dispersed and acts to prevent slip of defects within those grains, resulting in hardening of
10218-559: The buildings collapsed, several local TV and radio stations were knocked off the air until backup transmitters could be put into service. Such facilities also exist in Europe , particularly for portable radio services and low-power FM radio stations. In London , the BBC erected in 1936 a mast for broadcasting early television on one of the towers of a Victorian building, the Alexandra Palace . It
10349-519: The central mast structure to the guys and were built in the 1960s. The crossbars of these masts are equipped with a gangway that holds smaller antennas, though their main purpose is oscillation damping. The design designation of these masts is 30107 KM and they are exclusively used for FM and TV and are between 150–200-metre (490–660 ft) tall with one exception. The exception being the mast in Vinnytsia which has height of 354 m (1161 ft) and
10480-521: The characteristics of steel. Common alloying elements include: manganese , nickel , chromium , molybdenum , boron , titanium , vanadium , tungsten , cobalt , and niobium . Additional elements, most frequently considered undesirable, are also important in steel: phosphorus , sulphur , silicon , and traces of oxygen , nitrogen , and copper . Plain carbon-iron alloys with a higher than 2.1% carbon content are known as cast iron . With modern steelmaking techniques such as powder metal forming, it
10611-436: The characters from Eiichiro Oda 's manga. Patrons enjoyed various games or attractions based on their favorite characters and enjoyed meals from the world of One Piece . There was a gift store that features exclusive goods for One Piece fans. Tokyo Tower requires 28,000 liters (7,400 U.S. gal) of paint to completely paint the structure white and international orange , complying with air safety regulations. Before
10742-415: The construction ofTokyo Tower. In the 2022 film Bubble , it is depicted as being destroyed by the titular reality-breaking bubbles. Radio masts and towers A mast radiator or radiating tower is one in which the metal mast or tower itself is energized and functions as the transmitting antenna. The terms "mast" and "tower" are often used interchangeably. However, in structural engineering terms,
10873-422: The desired properties. Nickel and manganese in steel add to its tensile strength and make the austenite form of the iron-carbon solution more stable, chromium increases hardness and melting temperature, and vanadium also increases hardness while making it less prone to metal fatigue . To inhibit corrosion, at least 11% chromium can be added to steel so that a hard oxide forms on the metal surface; this
11004-413: The final steel (either as solute elements, or as precipitated phases), impedes the movement of the dislocations that make pure iron ductile, and thus controls and enhances its qualities. These qualities include the hardness , quenching behaviour , need for annealing , tempering behaviour , yield strength , and tensile strength of the resulting steel. The increase in steel's strength compared to pure iron
11135-625: The finest steel in the world exported to the Roman, Egyptian, Chinese and Arab worlds at that time – what they called Seric Iron . A 200 BC Tamil trade guild in Tissamaharama , in the South East of Sri Lanka, brought with them some of the oldest iron and steel artifacts and production processes to the island from the classical period . The Chinese and locals in Anuradhapura , Sri Lanka had also adopted
11266-423: The first he derived the radiation resistance of a vertical conductor over a ground plane . He found that the radiation resistance increased to a maximum at a length of 1 / 2 wavelength , so a mast around that length had an input resistance that was much higher than the ground resistance, reducing the fraction of transmitter power that was lost in the ground system without assistance from
11397-503: The form of charcoal) in a crucible, was produced in Merv by the 9th to 10th century AD. In the 11th century, there is evidence of the production of steel in Song China using two techniques: a "berganesque" method that produced inferior, inhomogeneous steel, and a precursor to the modern Bessemer process that used partial decarburization via repeated forging under a cold blast . Since
11528-599: The hardenability of thick sections. High strength low alloy steel has small additions (usually < 2% by weight) of other elements, typically 1.5% manganese, to provide additional strength for a modest price increase. Recent corporate average fuel economy (CAFE) regulations have given rise to a new variety of steel known as Advanced High Strength Steel (AHSS). This material is both strong and ductile so that vehicle structures can maintain their current safety levels while using less material. There are several commercially available grades of AHSS, such as dual-phase steel , which
11659-418: The hazard that communications towers can pose to birds. There have also been instances of rare birds nesting in cell towers and thereby preventing repair work due to legislation intended to protect them. Steel Steel is an alloy of iron and carbon with improved strength and fracture resistance compared to other forms of iron. Because of its high tensile strength and low cost, steel
11790-566: The help of engineering company Nikken Sekkei Ltd., Naitō claimed his design could withstand earthquakes with twice the intensity of the 1923 Great Kantō earthquake or typhoons with wind speeds of up to 220 kilometers per hour (140 mph). The new construction project attracted hundreds of tobi ( 鳶 ), traditional Japanese construction workers who specialized in the construction of high-rise structures. The Takenaka Corporation broke ground in June 1957 and each day at least 400 laborers worked on
11921-533: The lack of both funds and materials. The tower's height was eventually determined by the distance the TV stations needed to transmit throughout the Kantō region, a distance of about 150 kilometers (93 mi). Tachū Naitō , renowned designer of tall buildings in Japan, was chosen to design the newly proposed tower. Looking to the Western world for inspiration, Naitō based his design on the Eiffel Tower in Paris, France. With
12052-418: The lights are changed to metal halide lamps to illuminate the tower with a white color. The reasoning behind the change is a seasonal one. Ishii reasoned that orange is a warmer color and helps to offset the cold winter months. Conversely, white is thought a cool color that helps during the hot summer months. Occasionally, Tokyo Tower's lighting is changed to specific arrangements for special events. The tower
12183-445: The low-resistance antenna cannot effectively compete for power with the high-resistance earth. To partially compensate, radiotelegraph stations used huge capacitively top-loaded flattop antennas consisting of horizontal wires strung between multiple 100–300 meters (330–980 ft) steel towers to increase efficiency. AM radio broadcasting began around 1920. The allocation of the medium wave frequencies for broadcasting raised
12314-439: The main production route. At the end of 2008, the steel industry faced a sharp downturn that led to many cut-backs. In 2021, it was estimated that around 7% of the global greenhouse gas emissions resulted from the steel industry. Reduction of these emissions are expected to come from a shift in the main production route using cokes, more recycling of steel and the application of carbon capture and storage technology. Steel
12445-409: The months following the construction of NHK's own transmission tower. This communications boom led the Japanese government to believe that transmission towers would soon be built all over Tokyo, eventually overrunning the city. The proposed solution was the construction of one large tower capable of transmitting to the entire region. Furthermore, because of the country's postwar boom in the 1950s, Japan
12576-450: The most part, however, p-block elements such as sulphur, nitrogen , phosphorus , and lead are considered contaminants that make steel more brittle and are therefore removed from steel during the melting processing. The density of steel varies based on the alloying constituents but usually ranges between 7,750 and 8,050 kg/m (484 and 503 lb/cu ft), or 7.75 and 8.05 g/cm (4.48 and 4.65 oz/cu in). Even in
12707-593: The normal tower installation and maintenance service. These are generally called "stealth towers" or "stealth installations", or simply concealed cell sites . The level of detail and realism achieved by disguised cellphone towers is remarkably high; for example, such towers disguised as trees are nearly indistinguishable from the real thing. Such towers can be placed unobtrusively in national parks and other such protected places, such as towers disguised as cacti in United States' Coronado National Forest . Even when disguised, however, such towers can create controversy;
12838-436: The oxidation rate of iron increases rapidly beyond 800 °C (1,470 °F), it is important that smelting take place in a low-oxygen environment. Smelting, using carbon to reduce iron oxides, results in an alloy ( pig iron ) that retains too much carbon to be called steel. The excess carbon and other impurities are removed in a subsequent step. Other materials are often added to the iron/carbon mixture to produce steel with
12969-529: The past, ruggedized and under-run filament lamps were used to maximize the bulb life. Alternatively, neon lamps were used. Nowadays such lamps tend to use LED arrays. Height requirements vary across states and countries, and may include additional rules such as requiring a white flashing strobe in the daytime and pulsating red fixtures at night. Structures over a certain height may also be required to be painted with contrasting color schemes such as white and orange or white and red to make them more visible against
13100-410: The possibility of using single vertical masts without top loading. The antenna used for broadcasting through the 1920s was the T-antenna , which consisted of two masts with loading wires on top, strung between them, requiring twice the construction costs and land area of a single mast. In 1924 Stuart Ballantine published two historic papers which led to the development of the single mast antenna. In
13231-449: The product but only locally relieves strains and stresses locked up within the material. Annealing goes through three phases: recovery , recrystallization , and grain growth . The temperature required to anneal a particular steel depends on the type of annealing to be achieved and the alloying constituents. Quenching involves heating the steel to create the austenite phase then quenching it in water or oil . This rapid cooling results in
13362-741: The production methods of creating wootz steel from the Chera Dynasty Tamils of South India by the 5th century AD. In Sri Lanka, this early steel-making method employed a unique wind furnace, driven by the monsoon winds, capable of producing high-carbon steel. Since the technology was acquired from the Tamilians from South India, the origin of steel technology in India can be conservatively estimated at 400–500 BC. The manufacture of wootz steel and Damascus steel , famous for its durability and ability to hold an edge, may have been taken by
13493-424: The roof to access the tower's outside stairwell. At approximately 660 steps, the stairwell is an alternative to the tower's elevators and leads directly to the Main Observatory. Based on the hit manga and anime One Piece , Tokyo Tower featured a small One Piece themed amusement park that opened in 2015 and closed in 2020. The amusement park offered a range of attractions, shops, and restaurants, all based on
13624-526: The roofs of tall buildings. In North America , for instance, there are transmitting antennas on the Empire State Building , the Willis Tower , Prudential Tower , 4 Times Square , and One World Trade Center . The North Tower of the original World Trade Center also had a 110-metre (360 ft) telecommunications antenna atop its roof, constructed in 1978–1979, and began transmission in 1980. When
13755-494: The sky. In some countries where light pollution is a concern, tower heights may be restricted so as to reduce or eliminate the need for aircraft warning lights. For example, in the United States the 1996 Telecommunications Act allows local jurisdictions to set maximum heights for towers, such as limiting tower height to below 200 feet (61 m) and therefore not requiring aircraft illumination under US Federal Communications Commission (FCC) rules. One problem with radio masts
13886-471: The solid-state, by heating the ore in a charcoal fire and then welding the clumps together with a hammer and in the process squeezing out the impurities. With care, the carbon content could be controlled by moving it around in the fire. Unlike copper and tin, liquid or solid iron dissolves carbon quite readily. All of these temperatures could be reached with ancient methods used since the Bronze Age . Since
14017-401: The steel. At the very high cooling rates produced by quenching, the carbon has no time to migrate but is locked within the face-centred austenite and forms martensite . Martensite is a highly strained and stressed, supersaturated form of carbon and iron and is exceedingly hard but brittle. Depending on the carbon content, the martensitic phase takes different forms. Below 0.2% carbon, it takes on
14148-556: The steel. The early modern crucible steel industry resulted from the invention of Benjamin Huntsman in the 1740s. Blister steel (made as above) was melted in a crucible or in a furnace, and cast (usually) into ingots. The modern era in steelmaking began with the introduction of Henry Bessemer 's process in 1855, the raw material for which was pig iron. His method let him produce steel in large quantities cheaply, thus mild steel came to be used for most purposes for which wrought iron
14279-555: The technology of that time, such qualities were produced by chance rather than by design. Natural wind was used where the soil containing iron was heated by the use of wood. The ancient Sinhalese managed to extract a ton of steel for every 2 tons of soil, a remarkable feat at the time. One such furnace was found in Samanalawewa and archaeologists were able to produce steel as the ancients did. Crucible steel , formed by slowly heating and cooling pure iron and carbon (typically in
14410-457: The time's Aviation Law, the tower's two panoramic observatories are mostly frequented by tourists today. The tower constitutes a clear reference point in the center's skyline, forming a strong landmark, both night and day. Every five years, the tower is repainted in a process that takes about a year to complete. Tokyo Tower is next planned to be repainted in 2024. Tokyo Tower's two main revenue sources are antenna leasing and tourism. It functions as
14541-408: The top half of the tower was lit green to correspond with the Japanese premiere of The Matrix Reloaded and different sections of the tower were lit red, white and black to commemorate the first day of sales of Coca-Cola C2 . The tower was lit for the new millennium in 2000 with Motoko Ishii again reprising her role as the designer. In December 2008, Nihon Denpatō spent $ 6.5 million to create
14672-465: The tower was completely unlit except for the Main Observatory, which was lit with a bright white light. The resulting white ring represented the White Band referenced in the day's name. The two floors of windows that make up the exterior of the Main Observatory are utilized to display words or numbers. When the tower employed lighting to commemorate terrestrial digital broadcasting first being available in
14803-534: The tower was not suitable for Japan's planned terrestrial digital broadcasting planned for July 2011, and for the Tokyo area. A taller digital broadcasting tower, known as Tokyo Skytree , was completed on 29 February 2012. Tokyo Tower has become a prominent landmark in the city, and frequently appears in media set in Tokyo. A large broadcasting tower was needed in the Kantō region after NHK , Japan's public broadcasting station, began television broadcasting in 1953. Private broadcasting companies began operating in
14934-482: The tower's 30th anniversary in 1987, the only lighting on the tower were light bulbs located on the corner contours that extended from the base to the antenna. In the spring of 1987, Nihon Denpatō invited lighting designer Motoko Ishii to visit the tower. Since its opening 30 years earlier, the tower's annual ticket sales had dropped significantly, and in a bid to revitalize the tower and again establish it as an important tourist attraction and symbol of Tokyo, Ishii
15065-441: The tower's antenna include: Japan employs both analog and digital broadcasting. In July 2011 all television broadcasting was changed to solely digital. Tokyo Tower is not a reliable broadcasting antenna for completely digital broadcasting because the tower is not tall enough to transmit the higher frequency waves to areas surrounded by forests or high-rise buildings. As an alternative, a new 634-meter-tall (2,080 ft) tower called
15196-470: The tower. It was constructed of steel , a third of which was scrap metal taken from US tanks damaged in the Korean War . When the 90-meter-long antenna was bolted into place on 14 October 1958, Tokyo Tower was the tallest freestanding tower in the world, taking the title from the Eiffel Tower by nine meters. Though it is taller than the Eiffel Tower, Tokyo Tower weighs about 4,000 tons, 3,300 less than
15327-547: The tower. There, visitors can eat, shop, and visit several museums and galleries. Elevators that depart from the first floor of FootTown can be used to reach the first of two observation decks, the two-story Main Observatory. For the price of another ticket, visitors can board another set of elevators from the second floor of the Main Observatory to reach the final observation deck—the Special Observatory. Tokyo Tower,
15458-545: The tube and consequently the structure may look cleaner. These masts are mainly used for FM-/TV-broadcasting, but sometimes also as mast radiator. The big mast of Mühlacker transmitting station is a good example of this. A disadvantage of this mast type is that it is much more affected by winds than masts with open bodies. Several tubular guyed masts have collapsed. In the UK, the Emley Moor and Waltham TV stations masts collapsed in
15589-522: The upper carbon content of steel, beyond which is cast iron. When carbon moves out of solution with iron, it forms a very hard, but brittle material called cementite (Fe 3 C). When steels with exactly 0.8% carbon (known as a eutectoid steel), are cooled, the austenitic phase (FCC) of the mixture attempts to revert to the ferrite phase (BCC). The carbon no longer fits within the FCC austenite structure, resulting in an excess of carbon. One way for carbon to leave
15720-404: The whole of the structure is necessary. Small structures are typically accessed with a ladder . Larger structures, which tend to require more frequent maintenance, may have stairs and sometimes a lift, also called a service elevator. Tall structures in excess of certain legislated heights are often equipped with aircraft warning lamps , usually red, to warn pilots of the structure's existence. In
15851-428: The world's steel in 2023. Further refinements in the process, such as basic oxygen steelmaking (BOS), largely replaced earlier methods by further lowering the cost of production and increasing the quality of the final product. Today more than 1.6 billion tons of steel is produced annually. Modern steel is generally identified by various grades defined by assorted standards organizations . The modern steel industry
15982-425: Was also used at Criggion radio station . For ELF transmitters ground dipole antennas are used. Such structures require no tall masts. They consist of two electrodes buried deep in the ground at least a few dozen kilometres apart. From the transmitter building to the electrodes, overhead feeder lines run. These lines look like power lines of the 10 kV level, and are installed on similar pylons. For transmissions in
16113-405: Was designed in 1956 by the local civil engineer Fritz Leonhardt . Fiberglass poles are occasionally used for low-power non-directional beacons or medium-wave broadcast transmitters. Carbon fibre monopoles and towers have traditionally been too expensive but recent developments in the way the carbon fibre tow is spun have resulted in solutions that offer strengths exceeding steel (10 times) for
16244-697: Was developed in Southern India and Sri Lanka in the 1st millennium BCE. Metal production sites in Sri Lanka employed wind furnaces driven by the monsoon winds, capable of producing high-carbon steel. Large-scale wootz steel production in India using crucibles occurred by the sixth century BC, the pioneering precursor to modern steel production and metallurgy. High-carbon steel was produced in Britain at Broxmouth Hillfort from 490–375 BC, and ultrahigh-carbon steel
16375-502: Was formerly used. The Gilchrist-Thomas process (or basic Bessemer process ) was an improvement to the Bessemer process, made by lining the converter with a basic material to remove phosphorus. Another 19th-century steelmaking process was the Siemens-Martin process , which complemented the Bessemer process. It consisted of co-melting bar iron (or steel scrap) with pig iron. These methods of steel production were rendered obsolete by
16506-430: Was hired to redesign Tokyo Tower's lighting arrangement. Unveiled in 1989, the new lighting arrangement required the removal of the contour-outlining light bulbs and the installation of 176 floodlights in and around the tower's frame. From dusk to midnight, the floodlights illuminate the entire tower. Sodium vapor lamps are used from 2 October to 6 July to cover the tower in an orange color. From 7 July to 1 October,
16637-444: Was initially a wire suspended from a tall wooden pole. He found that the higher the antenna was suspended, the further he could transmit, the first recognition of the need for height in antennas. Radio began to be used commercially for radiotelegraphic communication around 1900. The first 20 years of commercial radio were dominated by radiotelegraph stations, transmitting over long distances by using very long wavelengths in
16768-438: Was produced globally, with 630,000,000 tonnes (620,000,000 long tons; 690,000,000 short tons) recycled. Modern steels are made with varying combinations of alloy metals to fulfil many purposes. Carbon steel , composed simply of iron and carbon, accounts for 90% of steel production. Low alloy steel is alloyed with other elements, usually molybdenum , manganese, chromium, or nickel, in amounts of up to 10% by weight to improve
16899-676: Was produced in the Netherlands from the 2nd-4th centuries AD. The Roman author Horace identifies steel weapons such as the falcata in the Iberian Peninsula , while Noric steel was used by the Roman military . The Chinese of the Warring States period (403–221 BC) had quench-hardened steel, while Chinese of the Han dynasty (202 BC—AD 220) created steel by melting together wrought iron with cast iron, thus producing
17030-424: Was searching for a monument to symbolize its national recovery from World War II , as one of the countries most ravaged by the war. Hisakichi Maeda, founder and president of Nippon Denpatō, the tower's owner and operator, originally planned for the tower to be taller than the Empire State Building , which at 381 meters was the highest structure in the world at the time. However, the plan fell through because of
17161-504: Was the diamond cantilever or Blaw-Knox tower . This had a diamond ( rhombohedral ) shape which made it rigid, so only one set of guy lines was needed, at its wide waist. The pointed lower end of the antenna ended in a large ceramic insulator in the form of a ball-and-socket joint on a concrete base, relieving bending moments on the structure. The first, a 665 foot (203 m) half-wave mast was installed at radio station WABC 's 50 kW transmitter at Wayne, New Jersey in 1931. During
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