Aholming transmitter

From Wikipedia, the free encyclopedia

Aholming transmitter is a facility for broadcasting the program of Deutschlandfunk on 207 kHz with a power of 500 kW at day and 250 kW at night between Aholming and Ottmaring in Bavaria. Aholming transmitter, which can be received in most parts of Europe, was built between 1986 and 1988 as replacement of Erching transmitter. This was necessary as night time operation on 207 kHz requires according to the waveplan of Geneva a directional radiation pattern for whose realization a second mast was required. This mast could not be built on the site of Erching, as the site had to be cleared from tall structures as in its proximity the new airport of Munich was under construction. Aholming transmitter, which went in service on January 1st, 1989 uses as antenna a directional antenna consisting of two grounded masts, which are guyed in three levels 101, 203 and 239 metres above ground. Over the guy level, which is fixed with the mast in a height of 203 metres, the transmission power is fed into the mast. Therefore from the top of the helix building close to the mast three conductor ropes run upward to a point of the 203 metre guy level, which is situated 110 metre away from its anchor point of the mast. Both masts, which are equipped in 6 levels with flight safety lamps are nearly of the same height to wavelength ratio as those of Sender Donebach ( 0.1829 ). The distance between them is 483 metres. At daytime the directional pattern of Aholming transmitter shows only a slight maximum toward Northwest and Southeast. At nighttime, when transmission power has to be reduced to 250 kW, both masts are fed with a phase shift of 117°. By this measure a strong directional radiation pattern occurs with a power reduction to 2.5 kW in azimuth ranges between 72 and 88°, 130 kW in azimuth range between 115 and 160° and 100 kW between 160 and 230°. The transmitter building odf Aholming transmitter is 420 metres away from both masts. It has an area of 1300 m*m and a volume of 6725 m*m*m. The transmitter consists of 2 250 kW-units, which are mostly identic to the devices used at Sender Donebach. They use dynamic amplitude modulation, which is generated by using pulse-wide modulation, a technique also used in modern static inverters.