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Transmission towerA transmitting tower is, in contrast to a radio mast, a free standing construction, which serves either as carrier for transmitting antennas or directly as transmitting antenna (radiating transmitting tower). Besides there are also constructions, which consist of a free standing tower, on which a guyed mast sands. Such construction are however very rare. Transmitting towers are implemented either as steel framework construction or as reinforced concrete construction. In earlier years also wood towers were usual, which disappeared however today - with exception of the transmitting tower in Gliwice. Further execution forms are glass fiber constructions. Sometimes they are realized as transmitting towers for NDBs or medium-wave transmitters of small power. A special form of the transmitting tower is the telescope mast, with whose assistance in very short time a radio tower can be realized. Telescope masts are used predominantly for the setting up of transmitting straining for the reporting of large events and as replacement for radio towers destroyed by disasters. For the short term realization of a radio tower if necessary also a chaind balloon or a kite can serve. So it can carry on the one hand appropriate transmitting antennas, or hold on the other hand an antenna wire (for VLF, LW or MW) into an appropriate height. Such an arrangement is used occasionally by military agencies or radio amateurs. A guyed balloon as durable transmission mechanism uses to time the US-American transmitters TV Martí, which radiates a television program for Cuba by means of such a balloon. Transmitting towers can be implemented as grounded or as isolated construction. Isolated transmitting towers are used as antennas for long and medium wave. However such constructions are rather rare, since removed transmitting poles possess better radiation characteristics. Acquaintance of isolated transmitting towers are the citizen of Berlin radio tower, the Blosenbergturm in Beromuenster or the transmitting towers in Junglinster. Against earth isolated transmitting towers of concrete are not built because of the limited maximum stress of the insulators. For the maintenance to elements, which require maintenance, like antennas, guy anhors, operating rooms or flight safety lamps suitable entrance possibility is to be always created. This is realized at small transmitting towers and with such where only few such facilities are present, usually in form of a ladder, which is attached either outside or inside the construction. Towers with larger cross section and more frequent maintenance have stairs and often also an elevator. This elevator is realized in transmitting towers in reinforced concrete construction way as conventional rope elevator. Elevators in free standing steel framework towers are occasional and in guyed transmitting poles nearly always of statical reasions built as ascending elevator. In principle elevators can be installed also in radiating transmitting towers isolated against earth. However of it usually because of the usually small number of mechanisms, those is rather foreseen maintenance to require and the rarity of their mounting, which must be made either an interruption of the transmit mode necessarily or by special isolated platforms, under normal conditions. Transmitting towers, those except radio mechanisms still different installations, as plants of the water supply or routistic mechanisms order, always possess a stairway and in nearly all cases an elevator. The tourist cannot select as a rule however between the stairway and the elevator. Grounded transmitting towers from steel and concrete are frequently used for the admission of transmitting antennas within the UKW range and of directional antennas. They become occasional also for the admission of wire antennas for long- and medium wave, as well as carrying towers of planar arrays for short wave arranging emitters (in this use nearly always as steel tower) use. Concrete towers are usually used as carriers of transmitting antennas for UKW broadcast, TV, radio relay link and portable radio. Smaller towers are often built from finished concrete parts, while larger towers are usually manufactured in local concrete building method. Some transmitting towers - in particular such for radio relay link in concrete building method - have a highly situated operating room for the admission of transmitters, accessible by an elevator. In other cases the transmitters in a building are beside the transmitting tower. This is situated at UKW transmitting plants usually directly next to the transmitting tower, and at transmitters for long -, medium- and short wave for radiation-technical reasons usually in a distance of 30 to 600 meters. At later facilities one finds a little house with tuning elements beside (or sometimes under) the transmitting tower, the helix building. In some towers are instead or additionally areas with touristic facilities, lain highly, like an observation deck and a tower restaurant. Such towers are usually called TV tower, even if they do not serve for the radiation of television programs. Further gives transmitting towers, which find additionally as water tower use, like the TV tower in Heidelberg. In which way of construction a transmitting tower is built or whether instead of a free standing tower a removed transmitting pole is to be used, depends on many factors. For transmitting facilities for frequencies under 3 MHz one uses as a rule the removed transmitting pole - either against earth isolates, with prism aerial or feed up at the top. For transmitting towers with touristic installations nowadays a reinforced concrete tower is practically always used. In Germany this applies also to plants of the radio relay link, since concrete towers vary with same wind less strongly than steel towers. For other transmitting towers with pure UKW- and applications of radio relay links is not always comprehensible the choice of the design of the radio tower, since here every now and then also the aesthetic appearance of the construction and offers of appropriate companies play a role. For very high constructions as a rule the guyed radio mast is used In some cases it is possible to install transmitting antennas for radio services in the UKW range on the roofs of high buildings. In particular in North America this is made very often (transmitting antennas on the Empire State Building or the Sears Tower), in addition, in Europe are such facilities, in particular for portable radio services and UKW transmitters of small power quite common. Also pylons can serve if necessary for the admission of transmitting antennas. Usually are this portable radio antennas or directional antennas of the respective power supply firm. However different plants were already installed, like a radar facility of the water and shipping velvet Hamburg on a carrying mast of the Elbe crossing 1. High transmitting towers must be equipped with flight safety lamps. Their supply is not with grounded constructions a problem. With isolated towers the supply is made by in an induction coil, which forms if necessary with a parallel switched condenser an antiresonant circuit for the transmitter frequency and which between tower and earth is switched, shifted a cable. Catastrophic collapses of transmission towers
See also
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