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Radio Communication

  Many forms of information transmission today are based on radio i.e. the use of electromagnetic waves. The preceding history since the middle of 18th century comprises the observations by a great number of physicists investigating the phenomena of electricity and magnetism and their search for a fitting theoretical explanation.

Based on this work Maxwell in 1864 postulated the relation between electric and magnetic field expressed in a new mathematical form. He introduced the subsequently much debated concept of "displacement current" for a non closed circuit and derived a wave equation in free space with light-like properties. Hertz proved from 1888 the validity of Maxwell's theory and discovered the advantage of tuning reception to transmission frequency.

Marconi was the experimenter who foresaw the practical application for message transmission, in particular for ships at sea. He started experiments from 1895 onwards over increasing distances until in 1901 he successfully bridged the Atlantic from England. It is astonishing to realise this happened barely one century ago.

Fleming, working for Marconi reported in 1904 the use of an incandescent lamp with an added electrode as a detection device, replacing the clumsy "cohearer". Two years later de Forest added another electrode to Fleming's diode thus giving birth to the triode.

Further developments led to the situation in 1927 when the Measurements Building was founded.


Marconi's receiving station
Marconi's receiving station at New Foundland (antenna wire attached to a kite) source: Nature 1902

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