Radio - History

The Radio History

James Clerk Maxwell, the Scottish physicist, was born on the 13th of June 1831, in Edinburgh. He was very interested in Michael Faraday’s work on electromagnetism. Faraday explained that electric and magnetic effects result from lines of force that surround conductors and magnets. Maxwell drew an analogy between the behavior of the lines of force and the flow of a liquid, deriving equations that represent electric and magnetic effects. In 1855 he produced a paper which built on Faraday’s ideas, and in 1861 developed a model for a hypothetical medium, that consisted of a fluid happen if the fluid became elastic and magnetic effects. He also considered what would happen if the fluid became elastic and a charge was applied to it. This would set up a disturbance in the fluid, which would produce waves travel through the medium. The German physicist Friedrich Kohlraush and Wilhelm Weber calculated that these waves would travel at the speed of light. Maxwell finally published this work in his ‘Treatise on Electricity and Magnetism’ in 1873. In 1888 German physicist Heinrich Hertz made the sensational discovery of radio waves, a form of electromagnetic radiation with wavelengths too long for our eyes to see, confirming Maxwell’s ideas. He devised a transmitting oscillator, which radiated radio waves, and detected them using a metal loop with a gap at one side. Then the loop was placed within the transmitter’s electromagnetic field, sparks were produced across the gap. This proved that electromagnetic waves could be sent out into space, and be remotely detected. These waves were know as ‘Hertzian Waves’ and Hertz managed to detect them across the length of his laboratory. Italian born Guglielmo Marconi was fascinated by Hertz’s discovery, and realized that if radio waves could be transmitted and detected over long distances, wireless telegraphy could be developed. He started experimenting in 1894 and set up rough aerials on opposite sides of the family garden. He managed to receive signals over a distance of 100 metres, and by the end of 1895 had extended the distance over a mile. He approached the Italian Ministry of Posts and Telegraphs, informing them of his experiments. The ;Ministry was not interested and so his cousin, Henry Jameson-Davis arranged an interview with Nyllian Preece, who was Engineer-in-Chief to the British Post Office. He came to England in February 1896 and gave demonstrations in London at the General Post Office Building. His transmissions were detected 1.5 miles away, and on 2th September at Salisbury plain the range was increased to 8 miles. In 1897 he obtain a patent for wireless, and established the Wireless Telegraph and Signal Company at Chelmsford. The world’s first radio factory was opened there in 1898. On 11th may 1897test were carried out to establish that contacts were possible over water. A transmitter was set up at Lavernock Point, near Penarth and the transmissions were received on the other side of Bristol Channel at the Island of Holm, a distance of 3.5 miles. The Daily Express was the first newspaper to obtain news by wireless telegraphy in August 1898, and in December of that year communication was set up between Queen Victoria’s Royal yacht, off Cowes and Osborne House. The Queen received regular bulletins on the Prince of Wale’s health, by the radio, from the yacht, where he was convalescing. Also in December of that year, wireless communication was set up between the East Goodwin light ship and the South Foeland lighthouse. On 3rd March 1899 Marconi obtained a lot of publicity when the first life was saved by wireless telegraphy, which was used to save a ship in distress in the North Sea. By the summer cross channel communication had been established and the first ocean newspaper published bulletins sent by wireless. About this time Marconi began to develop tuned circuits for wireless transmission, so that a wireless can be tuned to a particular frequency, to remove all other transmissions except the one of interest. He patented this on 26th April 1900, under the name of ‘Tuned Syntonic Telegraphy’. On Thursday 12th December 1901, Marconi and his associates succeeded in transmitting a signal across the Atlantic Ocean. He sailed to Newfoundland with G.S. Kemp and P.W. Paget, and received a transmission from Podlhu, Cornwall. The transmission was received at Signal Hill using a kite aerial. The British government and admiralty were greatly impressed and many people wanted to invest in the new technology. Demand grew and large numbers of ship carried the new apparatus, which saved many lives at sea. One of the most famous occasions was when the Titanic sank . signal transmitted by its Marconi wireless help and saved many lives. Receivers at this time were mainly crystal sets, which were extremely insensitive and unselective. They were connected to a pair of headphones and required a long aerial.