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The Warsaw Radio Mast was the world's tallest structure until its collapse on 8 August 1991. It is the second tallest structure ever built, being surpassed as tallest by the Burj Khalifa, completed in 2010. The mast, which was designed by Jan Polak, was tall. Its construction, started in July 1970, was completed on 18 May 1974, and its transmitter entered regular service on 22 July of that year. It was located in Konstantynów, Gąbin, Poland, and was used by Warsaw Radio-Television (Centrum Radiowo-Telewizyjne) for longwave radio broadcasting on a frequency of AM-LW (long wave) 227 kHz before 1 February 1988 and AM-LW (long wave) 225 kHz afterwards. Its base was above sea level. Because a voltage potential of 120 kV existed between the mast and ground, it stood on a -high insulator. It operated as a mast radiator (half wave radiator), so its height was chosen in order to function as a half-wavelength antenna at its broadcasting frequency. The signals from its 2 megawatt transmitters could be received across essentially the entire globe. Its weight was debated: Polish sources claimed . ==Construction== The Warsaw radio mast was a guyed steel lattice mast of equilateral triangular cross section, with a face width of . The vertical steel tubes forming the vertices of the mast had a diameter of 245 millimetres (10 in); the thickness of the walls of these tubes varied between 8 and 34 mm (0.31 to 1.33 in) depending on height. The mast consisted of 86 elements, each of which had a length of . The mast had 3 arrays of guy wires, each attached to the mast at 5 levels: , , , , and above ground.〔()〕] Each guy was fixed on a separate anchor block at the ground and was ) in diameter. To prevent the guy wires from interfering with the radio transmissions, the guys were insulated at regular intervals. The weight of guys and insulators used to anchor the mast was . An elevator and separate protected ladders were installed in the interior of the mast to facilitate access to the various mast components, including the aircraft warning lamps. The elevator had a maximum speed of and required 30 minutes for a trip from the bottom of the structure to the top. In the lower half of the mast, there was a vertical steel tube, attached to the mast's outer structure with large insulators. This tube was grounded at the bottom, and connected electrically to the mast structure by an adjustable metal bar at a height of when the tower transmitted on 227 kHz longwave and at a height of 334.18 m when it switched to 225 kHz on February 1, 1988. This technique allowed adjusting the impedance of the mast for the transmitter and worked by applying a DC ground at a point of low radio frequency voltage, to conduct static charge to ground without diminishing the radio energy. Static electrical charge can build up to high values, even at times of no thunderstorm activity, when such tall structures are insulated from ground. Use of this technique provides better lightning protection than using just a spark gap at the mast base, as it is standard at most mast radiators insulated against ground. The mast was equipped in 16 levels with air traffic warning lights with 200 watts power. Their height above ground was , , , , , , ,, , , , , , , , and . At the top there was a flashing beacon consisting of two lamps with 1000 watts power. A special overhead radio frequency transmission line was used to transfer the signal from the transmitter building to the mast. The transmitter building, situated at , had a volume of and was approximately from the mast. The transmitter consisted of two 1,000 kilowatt units built by Brown Boveri and Cie. An atomic clock was used to generate the transmission frequency in order to provide a very accurate, stable signal source which could be used as a frequency standard by anyone within signal range. The station, which had an area of 65 hectares, also had a lattice tower of rectangular cross-section close to the transmitter building, at . This tower was used to provide a radio link for programme feeds from the studio, which ran from the Palace of Culture and Science, Warsaw via a radio relay tower at Wiejca. To supply power to the station a 110 kV substation was built. The substation was over-engineered due to the strategic importance of the station as Poland's central transmitter. Although the power consumption of the transmitting station was large (estimated 6,000 kW), the substation was capable of supplying much more than was required. Six small towers were erected around the periphery of the station's grounds in order to support aircraft warning lamps where the guy ropes were located. They are situated at , , , , , and . The official name of the facility was ''Radiofoniczny Ośrodek Nadawczy w Konstantynowie'' (Radiophonic Transmission Center Konstantynow), ''Radiowe Centrum Nadawcze w Konstantynowie'' (Radio Transmission Center Konstantynow) or ''Warszawska Radiostacja Centralna (WRC) w Gąbinie'' (Warsaw Central Radio Station Gabin). It broadcast Polskie Radio's Program I. Approximately ten years after completion of the mast, inspections revealed structural damage caused by wind-induced oscillations at the mast, the backstage insulators and the guys. Repair work was very difficult and replacement of the mast by a stronger construction of the same height was considered. However, this was not realized, as a result of Poland's economic situation. In 1988 the mast was repainted, but this could not be done to the desired extent, as there was not enough paint available. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Warsaw radio mast」の詳細全文を読む スポンサード リンク
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