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Radio masts and towers are, typically, tall structures designed to support antennas (also known as aerials) for telecommunications and broadcasting, including television. They are among the tallest man-made structures. Similar structures include electricity pylons and towers for wind turbines. Masts are usually named after the broadcasting organizations that use them, or after a nearby city or town. Until August 8, 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 (1968.5 ft) or taller.〔(Tallest structures in US, built or under-construction )〕 In the case of a mast radiator or radiating tower, the whole mast or tower is itself the transmitting antenna. ==Mast or tower?== The terms "mast" and "tower" are often 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. In US broadcast engineering, a tower is an antenna structure attached to the ground, whereas a mast is a vertical antenna support mounted on some other structure (which itself may be a tower, a building, or a vehicle). Masts (to use the civil engineering terminology) tend to be cheaper to build but require an extended area surrounding them to accommodate the guy wires. Towers are more commonly used in cities where land is in short supply. There are a few borderline designs that are partly free-standing and partly 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 (guys go to ground) *Torre de Collserola, a guyed tower with a guyed mast on top (tower portion is not free-standing) ==Materials== 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「Radio masts and towers」の詳細全文を読む スポンサード リンク
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