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THE TRANSMISSION GALLERY

BROOKMANS PARK

The Brookmans Park station was opened on 14th October 1929 and was the first of the BBC's high-power, two programme Regional transmitting stations. It radiated the London Regional Programme and the National Programme with powers of 30 kW and 45 kW respectively. The station, which stands on a 57-acre site, generated its own electric power. The two original aerials were each supported by two 200-ft lattice steel towers. This arrangement remained substantially unaltered until 1939.

In the autumn of that year a 140kW medium-wave transmitter was installed in an extension to the original building. From this time the station has derived all its electric power from the public electricity supply.

With the re-arrangement of services after the war the 140kW transmitter carried the Home Service. This was radiated from a 500ft mast-radiator, which improved the range of the transmissions. The original National transmitter was kept as a reserve. The Regional transmitter, with an increased power of 50kW, was used for the Light Programme transmissions from the aerial and mast reflector on the south side of the transmitter building. Except for a change in frequencies (wavelengths) in 1950 to 908kc/s (330metres) for the Home Service and 1214kc/s (247metres) for the Light Programme, this arrangement is still in operation.

In the transmitter hall are installed the two original transmitters and the power control switchboard for them. Beyond this is the machine room in which the filament, grid bias and high tension supplies are generated. Also in this room are the rectifiers which were installed when electric power was first taken from the public supply. At the rear of the building is the engine room with four six-cylinder diesel generators each rated at 200 kW. These were formerly used to provide the electric power for the station but are now used only in case of failure of the mains supply.

The water cooling equipment for the valves of the original transmitters is installed beneath the transmitter hall and the associated water cooler stands outside at the rear of the building.

The Home Service transmitter and control cubicle together with the associated auxiliary equipment are on the first floor of the extension on the north side of the building. The power supply and valve cooling equipment are installed on the ground floor below the transmitter.

The Home Service transmitter serves the greater part of south-east England. During daylight the area extends to the counties of Suffolk, Lincoln, Leicester, Warwick, Worcester, Gloucester, Wiltshire, Hampshire, Surrey and Kent, although foreign interference severely reduces the area in which reception is satisfactory after dark.

The Light Programme transmitter serves an area including Greater London and extending to parts of the Home Counties. It provides a service which is less subject to the high level of electrical interference in urban areas than is the alternative Light Programme service on long waves (1500metres).

BBC Engineering Information Sheet No. 1001/1
May 1961

BP index | A History of Brookman's Park

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