Early
Developments
In the mid-1920s, the developments of the Shortwave Beam Wireless were quickly advancing.
Many advantages for sending high speed radio telegraphy had become apparent by
the use of shortwave. Prior to this, radio telegraphy had been associated with high capital cost transmitting stations operating
in very low frequencies (very long waves), using tremendous powers.
It was commonly believed that satisfactory 24-hr ship to shore communication
would only be achieved by such a system, where fading problems were not significant. However, transmission of high speed wireless
telegraphy was limited by the relatively low frequencies of the stations, and during the mid-1920s, it was recognized that
some other form of broadcasting would need to be developed, to compete satisfactorily with the submarine cable systems.
The concept of the Beam Wireless was introduced, in which radio frequency energy
was concentrated into a narrow path, using a complex system of antenna arrays, using shortwaves. The first such Beam transmitter
in the world was built at Bodmin, Moor, Cornwall, England, and the first beam receiver at Bridgewater, Somerset, England.
The first beam stations on the American continent were at Drummondville and Yamachiohe,
Canada, being replicas of the English facilities.
The overseas longwave stations typically operated with up 200 words per minute,
for 18 hrs a day on frequencies between 10 kHz and 40 kHz, with powers of several hundred kilowatts. Antenna systems were
enormous.
One such station, at Long Island, USA, of RCA, had 12 antennae for various parts
of the world. Each antenna was supported on 12 440 ft. towers, and was about 8 km in length. It operated on 17 kHz, with between
200 and 400 kW of power.
This should be contrasted with the Australian installation at Ballan, where the
antenna system had six masts 250 ft high, with a power of 20 kW, and operating on about 12 MHz,
England
The original concept for worldwide communication was with the usage of super high power on very low frequencies. Then,
because of the subsequent experimentation with the broadcast of radio signals on shortwave frequencies, it was realized that
a more reliable form of international communication could be achieved with the usage of lower power on shortwave frequencies,
at a considerably lower cost.
Thus it was, that the Imperial Wireless
Scheme, with a chain of super high powered longwave stations stretching from England to Australia via the Middle East, Africa
and Asia was cancelled in the early 1920s, and in its place the Marconi company implemented a series of Beam Wireless Stations
at the same locations. These stations were to be installed with the usage of the new valve or tube equipment, and the stations
were to be located no more than 2,000 miles apart.
In the early and mid 1920s, several new
Beam Wireless Stations were erected in England with the intent that each would be a key station for a communication service
with a specific part of the world. Several of these stations were in use on occasions with the relay of radio programming
for broadcast elsewhere, and for the transmission of news and commentaries from one part of the world to another.
The first of these new Beam Wireless Stations
in England was installed at Leafield in Oxfordshire. Interest in this location began in the year 1912 when Marconi conducted
experimental wireless transmissions in Morse Code. The partially built location was protected by the Home Guard during World
War I, and a massive high powered longwave spark wireless station was installed in 1922 under the callsign GBL. Soon afterwards,
electronic transmitters were installed, and these were on the air on shortwave under the callsigns GBM and GBO.
During World War II, Leafield was an important
communication station, and in the 1960s it was upgraded and modernized, mainly for maritime communication, and it became one
of the major stations known as Portishead Radio. The receiver station for Leafield was located at Devizes in Wiltshire. This
Leafield station was finally closed in 1986 and the property was sold to a local college. Soon afterwards it was sold again,
and it is now in use as a closed circuit for motor car racing.
Another Beam Wireless Station was installed
at Bodmin in Cornwall and this station served as the England terminal for communication with Canada and South Africa under
the callsigns GBJ and GBK. This station was opened for service at the end of a week long series of test transmissions in October
1927. The receiver station for Bodmin was located at Bridgewater.
During the late 1930s, the equipment at
this station was dismantled, removed, transferred and re-erected at Dorchester, as a safety procedure due to political developments
on continental Europe.
Another important Beam Wireless Station
was erected at Grimsby in Cornwall in 1927. This was a very large station with a series of curtain antennas stretching for
one mile. In actual reality, this was a double station with twin 20 kW transmitters. The Grimsby side communicated with Australia,
and the Tetney side communicated with India.
This station was established and operated
by the Marconi Company, and it was later taken over by Cable & Wireless. The callsigns in use at Grimsby-Tetney were GBH
and GBI, and the receiver station was located at Winthorpe.
Another Beam Wireless Station during this
era was constructed by the Marconi Company at Dorchester in the south of England. This was a very large station with two transmitter
buildings and a bevy of curtain antenna systems on 460 acres of land.
The first transmitter hall at Dorchester
initially contained four Marconi transmitters at 10 kW each, and the second transmitter hall contained eight transmitters
at a similar power rating. Subsequently, at least a dozen higher powered transmitters rated around 30 kW were installed. The
receiver station for the Dorchester transmitting station was located at nearby Somerton.
The Dorchester station was constructed
specifically as the England terminal for communication circuits with Japan and Egypt, though subsequently, Asia, South Africa,
North America and Australia were added. The main callsign for the American circuit at the Dorchester station was GLH, and
for the South American circuit, GLW. This station was finally closed in April 1978.
The original concept for the terminals
of the Beam Wireless Stations in England called for six separate stations, though this number was soon afterwards expanded
to nine stations, and even more.
