Bose’s microwave demonstration (1895)
Up to 1900 the focus of invention had been on sending and receiving
communication signals. As the 20th century progressed scientists
worked with longer radio wavelengths (lower frequency signals) to
achieve ever-greater distances. But some scientists were going the
other way, looking at the properties of very short wavelengths. The
theory was that by shortening the wave, you could pack more
electromagnetic energy into the signal. One of the pioneers was J.C.
Bose in India. In 1895 he gave his first public demonstration of
very short wavelengths, ranging from 2.5cm down to 5mm - equivalent
to a frequency of 60 Gigahertz (GHz). He used these transmissions to
ring a bell remotely and to explode a charge of gunpowder.
The first microwave links (1930)
Microwave links first came into practical use during
the 1930s. In 1931 Britain's Standard Telephone & Cable Ltd (STC)
demonstrated its 'Micro-Ray' microwave communications link across
the Channel between Dover and Calais. The following year, Britain's
first ultra short wave radio telephone link was set up by The Post
Office across the Bristol Channel, spanning a distance of 13 miles.
first radar (1935)
In 1932 Sir Robert Watson-Watt figured out a way to harness the
power of very short waves to detect objects far away. He came up
with the idea of pulsing energy out on very short wavelengths in
order to 'bounce' it off a target and detect the reflected signals.
He wrote a paper (with A.F. Wilkins) describing this new technique
in 1935 and the idea was taken up rapidly.
By the autumn of 1938 his Radio Direction Finding (RDF) systems were
in place along the south and east coasts of Britain. During the
Battle of Britain in 1940, the British were able to detect enemy
aircraft at any time of day and night and in any weather conditions,
proving the defensive value of RDF or, as it would soon come to be
called, 'radar' - short for Radio Detection And Ranging.
Arthur C. Clerk’s proposal for
Once Werner von Braun's V2
missiles ceased raining destruction on London and other cities, a
young RAF technician called
Arthur C. Clarke conceived a
vision for the post-war future in a magazine called Wireless World.
In a letter headed 'V2 for Ionospheric Research', Clarke explained
how a network of satellites could be placed in stationary orbit,
22,300 miles above the Earth's surface. Later, in an article titled
'Extra-Terrestrial Relays' published in October 1945, Clarke
explained how these satellites could be used to transmit radio, TV
and telephone signals around the world.
Geostationary orbits (1945)
The notion of the geostationary (or geosynchronous) orbit was first
proposed in 1945 when the science fiction writer Arthur C. Clarke
published his visionary concept of relaying communication signals
from one ground station to another via artificial satellites
circling the Earth. Keeping a steady flow of information between two
ground stations and the satellite would need the satellite to remain
in a fixed position in sight of both stations.
Clarke reasoned that if the satellite orbited in the same direction
and the same orbital speed as the Earth's rotation, it would appear
to remain in a fixed position in the sky. He correctly calculated
that the satellite would exactly match the speed of the Earth's
rotation and keep in constant orbit at an altitude of 35,800km
(22,300 miles) above the equator.
NASA’s syncom programme (1963)
In July 1963 the Hughes Aircraft Corporation launched the
experimental Syncom 2 for NASA, the world's first geosynchronous
communications satellite. Its earlier sister, Syncom 1, had been
blown up on launch earlier that year, but version two was a huge
success. It carried the first live two-way satellite call between
heads of state when President John F. Kennedy in Washington, D.C.,
telephoned Nigerian Prime Minister Abubaker Balewa in Africa.
The third Syncom satellite transmitted live television coverage of
the 1964 Olympic Games from Tokyo. Syncom blazed the trail for the
new generation of communications satellites in geosynchronous orbit.