necessary to provide several fill-in transmitters for the more distant regions. It
was therefore decided that a single new ‘super high-power’ long-wave transmitter (taking 5XX as its call sign) should be built radiating the national
programme on long-wave from a site where it would serve most of the highly
populated areas of the UK. In this respect the seven regional areas; London, the
Midlands, South Wales and South West England, Yorkshire and Lancashire,
Glasgow, Edinburgh and Belfast were all to receive their national broadcast
from this new transmitter. Areas outside these regions being served by the
existing services. The ‘centre-of-gravity’ of this population map was
Birmingham but technical reasons made it difficult to locate a high-powered
transmitter in such a built-up area. An alternative site had to be found to the
south of Birmingham and the short-list included Barnt Green and Wychbold,
Droitwich Spa. In 1932, after the BBC conducted a series of transmission tests
with a mobile transmitter and discounted the existence of underground brine
streams, Droitwich was selected. The purchase of a 24-acre site was completed
in February 1933 and in addition to a national service by means of the long
wave transmitter (at an initial 200 kW), a regional service for the midlands was
to be provided by means of a medium wave transmitter (50 kW).
The later CAT valves were designed specifically for ‘super high-power’
broadcasting. Working closely with the BBC engineers, construction of the
valves and the transmitter began at Wembley under the direction of the valve
group. The system of modulation chosen by Marconi was Robert’s ‘series
modulation’ and it was expected to provide faithful reproduction of sound
broadcasts between 30 and 10,000 cycles. But the original (long wave)
transmitter output power was planned to be 200 kilowatts and this caused
concern in certain quarters. Some said Droitwich would be the ‘loudest voice
in the world’ and cause interference with other stations on an unprecedented
scale. As a compromise it was eventually agreed to operate at a lower radiated
power. Even so, some curious things happened.
By April 1933 the approach road to the new transmitter site was started; by
September the two 700-foot steel lattice aerial masts were nearing completion;
by November the transmitter building was well advanced; by July 1934 testing
of the transmitter began and an opening date for the station was set for 06
September 1934. In August, listeners who happened to tune to the long-wave
band of their radios (or ‘wireless sets’) in the early hours of the morning would
hear an announcement ‘This is the long-wave National transmitter at Droitwich
testing’ followed by a programme of ‘gramophone records’. Reports on the
reception from all over the country confirmed the high-quality signal that had
been the promise of the new Marconi series-modulation system. A trade boom
was already apparent and GEC/Marconi received orders to build similar
16 The GEC Laboratories 1930–1939
393
was therefore decided that a single new ‘super high-power’ long-wave transmitter (taking 5XX as its call sign) should be built radiating the national
programme on long-wave from a site where it would serve most of the highly
populated areas of the UK. In this respect the seven regional areas; London, the
Midlands, South Wales and South West England, Yorkshire and Lancashire,
Glasgow, Edinburgh and Belfast were all to receive their national broadcast
from this new transmitter. Areas outside these regions being served by the
existing services. The ‘centre-of-gravity’ of this population map was
Birmingham but technical reasons made it difficult to locate a high-powered
transmitter in such a built-up area. An alternative site had to be found to the
south of Birmingham and the short-list included Barnt Green and Wychbold,
Droitwich Spa. In 1932, after the BBC conducted a series of transmission tests
with a mobile transmitter and discounted the existence of underground brine
streams, Droitwich was selected. The purchase of a 24-acre site was completed
in February 1933 and in addition to a national service by means of the long
wave transmitter (at an initial 200 kW), a regional service for the midlands was
to be provided by means of a medium wave transmitter (50 kW).
The later CAT valves were designed specifically for ‘super high-power’
broadcasting. Working closely with the BBC engineers, construction of the
valves and the transmitter began at Wembley under the direction of the valve
group. The system of modulation chosen by Marconi was Robert’s ‘series
modulation’ and it was expected to provide faithful reproduction of sound
broadcasts between 30 and 10,000 cycles. But the original (long wave)
transmitter output power was planned to be 200 kilowatts and this caused
concern in certain quarters. Some said Droitwich would be the ‘loudest voice
in the world’ and cause interference with other stations on an unprecedented
scale. As a compromise it was eventually agreed to operate at a lower radiated
power. Even so, some curious things happened.
By April 1933 the approach road to the new transmitter site was started; by
September the two 700-foot steel lattice aerial masts were nearing completion;
by November the transmitter building was well advanced; by July 1934 testing
of the transmitter began and an opening date for the station was set for 06
September 1934. In August, listeners who happened to tune to the long-wave
band of their radios (or ‘wireless sets’) in the early hours of the morning would
hear an announcement ‘This is the long-wave National transmitter at Droitwich
testing’ followed by a programme of ‘gramophone records’. Reports on the
reception from all over the country confirmed the high-quality signal that had
been the promise of the new Marconi series-modulation system. A trade boom
was already apparent and GEC/Marconi received orders to build similar
16 The GEC Laboratories 1930–1939
393