Radio communications are used to broadcast terrestrial and satellite radio and television as well as mobile phone signals.
Radio communications are used to broadcast terrestrial and satellite radio and television as well as mobile phone signals.
They were pioneered by a brilliant young Italian, Guglielmo Marconi, who made Britain his home.
Radio waves are produced whenever an electric current flows to-and-fro. They travel out in all directions at 300,000 kilometres per second (186,000 miles per second), the speed of light.
In modern communications, radio waves are produced by currents in wires called antennas.
But the first radio waves made deliberately were produced by electric current jumping through the air as a spark.
Scottish physicist James Clerk Maxwell (1831–1879) predicted the existence of radio waves in 1864 after working out the mathematical relationship between electric and magnetic fields.
But German physicist Heinrich Hertz (1857–1894) was first to prove they exist, in a remarkable experiment in 1888.
Hertz made a spark jump the gap between two metal electrodes, producing a burst of radio waves.
He set up a similar gap 1.5 metres (5 feet) away, which was connected to a battery and on the verge of sparking.
When the radio waves from the first gap reached the second gap, they caused a spark there.
The second spark always followed immediately after the first – showing a radio signal was passing ‘wirelessly’ through the air.
Marconi (1874–1937) was the man who set up the world’s first radio stations to broadcast ‘wireless telegraphy’ – bursts of radio waves sent across large distances, carrying Morse code.
He began experimenting with radio in Italy in 1894, reproducing and improving Hertz’s experiment. By attaching one end of each spark gap to a long wire, he made the apparatus much more sensitive – he had made the world’s first antennas.
Marconi extended the distance across which he could detect the radio waves – first to 9 metres (30 feet), then to 2.4 kilometres (1.5 miles).
He replaced the spark gaps with a more sensitive device called a ‘coherer’ and began sending messages as on-and-off pulses of Morse code.
In 1896 Marconi moved to England where he soon impressed executives of the Post Office and the Army with demonstrations on Salisbury Plain, Wiltshire, and across the Channel.
In 1901 he managed to send a message across the Atlantic, from Cornwall to Newfoundland, now in Canada.
He received the Nobel Prize for Physics in 1909.
In 1906 American inventor Lee de Forest (1873–1961) invented an electronic gadget called the Audion.
The device enabled engineers to produce radio waves of pure frequencies and manipulate them to carry sound rather than just Morse code.
It was not until 1915 that radio engineers were transmitting sound effectively, however.
The transistor was invented in 1948. It does the same thing as the Audion but is much smaller and uses less power.
The transistor made radio receivers more portable.
Today, most of the manipulation of radio signals is done on miniature circuits on microchips.
