Radio transmission and reception. We all take it for granted when listening to radio. Italian wireless pioneer Guglielmo Marconi used to experiment with sending and receiving radio messages, without that tinkering we would be without the wonders of radio and television. In 1895 Marconi achieved radio communication over more than a mile, and in England in 1896 he conducted successful experiments that led to the formation of the company that became Marconi's Wireless Telegraph Company Ltd. He shared the Nobel Prize for Physics in 1909 for the development of wireless telegraphy. After reading about radio waves, Marconi built a device to transmit these electromagnetic waves and receive them as electrical signals. He then tried to transmit and receive radio waves over increasing distances. In 1898 he successfully transmitted signals across the English Channel, and in 1901 established communication with St John's, Newfoundland, from Poldhu in Cornwall, and in 1918 with Australia

The pioneer of radio telegraphy, spoke from his 700-ton yacht, Elettra in Genoa, Italy, to an audience in Sydney, Australia. The yacht, purchased in 1919, was converted into a floating laboratory where he tested short-wave reception and transmission. By the end of the 1920s he had set up a worldwide system of short-wave stations.

The radio frequency oscillator generates rapidly varying electrical signals, which are sent to the transmitting aerial. In the aerial, the signals produce radio waves (the carrier wave), which spread out at the speed of light. The sound signal is added to the carrier wave by the modulator. When the radio waves fall on the receiving aerial, they induce an electrical current in the aerial. The electrical current is sent to the tuning circuit, which picks out the signal from the particular transmitting station desired. The demodulator separates the sound signal from the carrier wave and sends it, after amplification, to the loudspeaker.

Transmission and reception of radio waves. In radio transmission a microphone converts sound waves (pressure variations in the air) into a varying electric current, which is amplified and used to modulate a carrier wave which is transmitted as electromagnetic waves, which are then picked up by a receiving aerial, amplified, and fed to a loudspeaker, which converts them back into sound waves.

The theory of electromagnetic waves was first developed by Scottish physicist James Clerk Maxwell in 1864, given practical confirmation in the laboratory in 1888 by German physicist Heinrich Hertz, and put to practical use by Italian inventor Guglielmo Marconi, who in 1901 achieved reception of a signal in Newfoundland, Canada, transmitted from Cornwall, England.

To carry the transmitted electrical signal, an oscillator produces a carrier wave of high frequency; different stations are allocated different transmitting carrier frequencies. A modulator superimposes the audio-frequency signal on the carrier. There are two main ways of doing this: amplitude modulation (AM), used for long- and medium-wave broadcasts, in which the strength of the carrier is made to fluctuate in time with the audio signal; and frequency modulation (FM), as used for VHF broadcasts, in which the frequency of the carrier is made to fluctuate. The transmitting aerial emits the modulated electromagnetic waves, which travel outwards from it.

	The Historic Poldhu Wireless Station www.hamradio.piatt.com Location of the first Transatlantic radio transmission on 12th December 1901. At 12:30 a.m GMT on December 12, 1901, in St. John's Newfoundland, Guglielmo Marconi distinguished three faint clicks through the earphones of his wireless receiver -- the Morse Code letter "S" -- and a new era was born.
	Guglielmo Marconi (1874 to 1937) www.gb4imd.org.uk In the first year of the 20th century, a well-tailored young man of 27 named Guglielmo Marconi sat in a shack on a cliff in Newfoundland trying to receive a message on his new invention, the wireless telegraph