Aerial Systems
The station has two directional aerial systems: one for 648 kHz and one for 1296 kHz.
The directional aerial for 648 kHz (erected in 1981-82) consists of a row of five 106.7 metre (350 ft) freestanding steel lattice towers of triangular cross section, insulated at their base. All five towers are driven. It is beamed at 131 degrees (i.e. south-east) though for practical purposes the exact bearing is nominal as the beam is very broad towards the east and south. It provides daytime coverage of Belgium, the Netherlands, Luxembourg, north-east France and north-west Germany by ground wave propagation; and night-time coverage of much of Europe by skywave propagation.
The directional aerial for 1296 kHz (erected in 1978) consists of six freestanding steel lattice towers. Unlike the directional aerial for 648 kHz, they are arranged in two parallel rows with three towers in each. Only the middle tower of each three is driven: the other towers act as passive reflector and director elements. It is beamed at 96 degrees (i.e. east) and was originally mainly intended for night-time (skywave) coverage of Poland, Czechoslovakia, Hungary and the western USSR, key target areas for the BBC during the Cold War. It can also be used for daytime coverage of the Netherlands and Belgium.
Both the 648 and 1296 directional aerials have limited radiation to the west, meaning that, despite the high power of the transmitters, reception of Orfordness within the UK was poor or non-existent, with the notable exception of parts of south-east England (including London) and East Anglia.
There is also a back-up omni-directional mast radiator for 648 kHz (erected in 1983), which can only handle transmitter powers of up to 250 kW. This was only used when maintenance work was being carried out on the directional antenna.
Read more about this topic: Orfordness Transmitting Station
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