Radio masts and towers
Radio masts and towers are tall structures designed to support antennas for telecommunications and broadcasting, including television. There are two main types: self-supporting structures, they are among the tallest human-made structures. Masts are named after the broadcasting organizations that built them or use them. In the case of a mast radiator or radiating tower, the whole mast or tower is itself the transmitting antenna; the terms "mast" and "tower" are used interchangeably. However, in structural engineering terms, a tower is a self-supporting or cantilevered structure, while a mast is held up by stays or guys. Broadcast engineers in the UK use the same terminology. A mast is a ground-based or rooftop structure that supports antennas at a height where they can satisfactorily send or receive radio waves. Typical masts are of tubular steel construction. Masts themselves play no part in the transmission of mobile telecommunications. Masts tend to be cheaper to build but require an extended area surrounding them to accommodate the guy wires.
Towers are more used in cities where land is in short supply. There are a few borderline designs that are free-standing and guyed, called additionally guyed towers. For example: The Gerbrandy tower consists of a self-supporting tower with a guyed mast on top; the few remaining Blaw-Knox towers do the opposite: they have a guyed lower section surmounted by a freestanding part. Zendstation Smilde, a tall tower with a guyed mast on top with guys which go to ground. Torre de Collserola, a guyed tower with a guyed mast on top where the tower portion is not free-standing. Experimental radio broadcasting began in 1905, commercial radio broke through in the 1920s; until August 8, 1991, the Warsaw radio mast was the world's tallest supported structure on land. There are over 50 radio structures in the United States that are taller; the steel lattice is the most widespread form of construction. It provides great strength, low weight and wind resistance, economy in the use of materials. Lattices of triangular cross-section are most common, square lattices are widely used.
Guyed masts are used. When built as a tower, the structure may be 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 constructed out of steel tubes; this construction type has the advantage that cables and other components can be protected from weather inside the tube and the structure may look cleaner. These masts are used for FM-/TV-broadcasting, but sometimes 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 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 and the Soviet Union, many tubular guyed masts were built, while there are nearly none in Poland or North America.
In several cities in Russia and Ukraine several tubular guyed masts with crossbars running from the mast structure to the guys were built in the 1960s. All these masts, which are designed as 30107 KM, are used for FM and TV transmission and, except for the mast in Vinnytsia, are between 150–200-metre tall; the crossbars of these masts are equipped with a gangway that holds smaller antennas, though their main purpose is oscillation damping. Reinforced concrete towers are 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, when the structure 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 the CN Tower in Canada. In addition to accommodating technical staff, these buildings may have public areas such as observation decks or restaurants; the Stuttgart TV tower was the first tower in the world to be built in reinforced concrete. It was designed in 1956 by the local civil engineer Fritz Leonhardt. Fiberglass poles are 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 similar or exceeding steel for a fraction of the weight which has allowed monopoles and towers to be built in locations that were too expensive or difficult to access with the heavy lifting equipment, needed for a steel structure. Wood has been superseded in use by metal and composites for tower construction. Many wood towers were built in the UK during World War II because of a shortage of steel.
In Germany before World War II wooden towers were used at nearly all medium-wave transmission sites which hav
The Fernsehturm Heidelberg is a transmission tower for FM and DVB-T on the Königstuhl hill of Heidelberg at 49°24′16″N 8°43′46″E. It was the property of the City of Heidelberg and sold to the SWR; because of its exposed location on the crest of the hill the tower itself is only 82 meters high. The Heidelberg TV tower has an open-air observation deck 30 metres up its height, which can be reached by an elevator; the observation deck is now permanently closed for visitors due to safety concerns. The sale of the tower sealed the fate of the observation deck which used to enable tourist a spectacular 360 degrees view of the region. In the first years of its existence the tower was used as a water tower; the water tank is located within the main body behind the observation deck. 11 digital TV channels on 3 Multiplexes are broadcast from the TV tower. DVB-T Frequencies are channel 21 for the ZDF 49 and 60 for the ARD/SWR transponders. TV channels broadcast are ARD, ZDF, SWR, HR, WDR, BR, 3Sat, Doku/Kika, Phoenix and EinsPlus.
Each Multiplex is broadcast with plans to double that to 100 kW near or mid-term. On November 5, 2008, frequencies were changed for all 3 transponders; that transition canceled the SFN with the Stuttgart region. 4 analog FM radio channels are broadcast from this tower. SWR1 97.8 MHz, SWR2 88.8 MHz, SWR3 99.9 MHz and SWR4 104.1 MHz. One digital radio multiplex is broadcast from this tower on DAB channel 12A. Available channels on that digital channel are SWR 1 Baden–Württemberg, SWR 2, SWR 3, DASDING and SWR cont.ra. The Telecom Telecommunication Tower Heidelberg and former Telecommunication Tower of US-Forces Heidelberg are located close by. Both are off limits to the public. List of towers Fernsehturm Heidelberg at Structurae http://www.skyscraperpage.com/diagrams/?b7805