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Early beginnings
It is impossible to say exactly where the story of radio starts. The early scientists who saw and investigated the effects of electricity and magnetism were crucial to the story. But a number of people also noticed effects that were probably caused by radio waves. Galvani is thought to have witnessed the effects of electromagnetic waves as he was investigating the conduction of electricity. Others too including Henry, Edison and others may also have witnessed effects as well. -
Maxwell proves the existence of e/m waves
It was James Clerk Maxwell who first proved the existence of an electromagnetic (e/m) wave. He proved it mathematically, and published his findings in a number of papers. Much of this early work was performed whilst he was at Kings College London. His work was summarised in a book entitled "Treatise on Electricity and Magnetism." In 1871 Maxwell moved to Cambridge where he became the first director of the Cavendish Research Laboratory. -
1887 Hertz discovers radio waves
In a series of experiments started in 1887 Heinrich Hertz proved the physical existence of radio waves that Maxwell had shown to exist mathematically. His transmitter consisted of a simple spark gap across an induction coil with a loop of wire to act as an antenna. The receiver consisted of a smaller gap in a loop the same size as that in the transmitter. In his experiments Hertz also discovered many of their properties. -
1894 Marconi's first experiments
- In the autumn of 1894 Marconi performed his first experiments with radio waves in the attic of his parents house in Bologna. Initially he was only able to achieve distances of a few metres, but he made significant progress, steadily increasing the distance over which he send the signals. He managed to send signals over a distance of about 2 kilometres, and realising the possibilities of the system for maritime communications he gave a demonstration to the Italian authorities.
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1897 Marconi demonstrates radio waves travel over water
Marconi gave his first public demonstrations in December 1896. One major use for radio could be in crossing stretches of water. Cables were expensive and very vulnerable. in the summer of 1897 Marconi set up a link spanning the 14 kilometres of the Bristol Channel. After this Marconi put on many other demonstrations and gave lectures: many were to the press and in this way he was able to gain the maximum amount of publicity. It also stimulated the interest of other experimenters. -
1899 First cross channel link
Marconi steadily increased the range of his wireless system. In the spring of 1899 a first link was set up to cross the English Channel between an existing station at South Foreland in England and a station set up at Wimereux near Bologne in France. This was the first international wireless transmission. Another demonstration was organised later in the year and it was found that the signals from Wimereux could be heard back at Marconi's factory in Chelmsford over 130 kilometres away. -
1901 First transatlantic transmission
With the successes in using radio waves to cross the English channel Marconi turned his eyes towards greater distances and being able to send messages across the Atlantic. If he could succeed in this he would be able to use his system to send messages across the Atlantic more cheaply than using a cable, and also keep in contact with ships over vast distances. Marconi started this venture by setting up stations at Polhu in Cornwall England and Cape Cod in Massachussetts, USA. -
1904 Fleming invents the diode valve
Professor Ambrose Fleming of University College London acted as a consultant to Marconi and he was very aware that detectors used in the receivers were the weak link in the receiving equipment of the day. Having seen the Edison effect - an effect Edison discovered when he was trying to extend the life of electric light bulbs, Fleming wondered whether this could be sued to detect radio signals. He gave details to his assistant who set up an experiment that worked. -
1906 De Forest invents the triode
In the USA de Forest, replicated Fleming's diode and went a stage further by adding an additional element to give a device he called and Audion. Although de Forest applied for several patents in the years between 1905 and 1907, the invention of the triode is normally taken to be 1906. Initially the triode was only used as a detector. Its operation was not understood, and this prevented its full potential from being utilised. -
1912 The triode used as an amplifier
It took some time before the full potential of the triode was realised. Eventually it was de Forest who succeeded in using it as an amplifier and in 1912 he built an amplifier using two devices. This was demonstrated to AT&T who understood its potential for use as a repeater in long distance telephone circuits. -
1918 Armstrong invents the superhet
Although thermionic valves (tubes) enabled far greater performance to be gained in radio receivers, the performance of the devices was still very poor and receivers of the day suffered from insensitivity and poor selectivity. During the First World War a considerable amount of effort was devoted into resolving these problems. An intermediate solution was developed by a Frenchman named Lucien Levy, but in 1918, Edwin Armstrong developed a receiver w -
1920 Early broadcasts by the Marconi Company
The possibilities of broadcasting entertainment and news using radio soon arose. In Britain initial transmissions were made by the Marconi Company from their Chelmsford works for experimental purposes. These broadcasts started in February 1920. Although only two daily programmes were broadcast they had an enormous impact. The famous international singer Dame Nellie Melba took part in one on 20th June 1920. -
1921-23 Short wave transatlantic success
Long distance communications had until now been concentrated on the long wavelengths. Accordingly radio amateurs had been only allowed to use the short wave bands which were thought to be of little commercial value. However in the USA a number of amateur stations had made contacts over considerable distances. This made people wonder whether it would be possible to make contact across the Atlantic. After several sets of tests commencing in 1921 contact was finally made -
1922 2LO and the BBC
In May 1922 the Marconi Company was allowed to set up a broadcast station in London. Later in the year the British Broadcasting Company was formed and this took over the station that had the famous call 2LO. Initially it only had a power of 100 watts, which gave it a maximum coverage of about 40 miles. Later with a power of 1.5 kW its coverage was greatly increased -
1925 International Broadcasting
The Westinghouse Company set up a short wave broadcasting station (KDKA) in East Pittsburgh which transmitted on a wavelength of 62.7 metres. This was successfully received and rebroadcast in Britain. In Britain the amateur station 2NM run by Gerald Marcuse started broadcasts in 1927. These gained great popularity and shortly after their start the BBC commenced broadcasts from an experimental station. -
1934 Frequency Modulatio
wideband FM is widely used today it took many years for its advantages to be discovered, previously everyone had tried to improve its performance by reducing the bandwidth. It was Edwin Armstrong who made the breakthrough. However it took many years for him to convince people about its superiority. In 1934 he brought his idea to the attention of RCA, and a year later he set up a demonstration. Then in 1939 he used his own money to finance a station to prove that the system worked. -
1945 Arthur C Clarke proposes geostationary satellites
Up until this time all international communications relied on either short wave radio transmissions or cable links. Short wave radio was unreliable and subject to high levels of interference, international telephone cables were exceedigly expensive. In 1945 the author Arthur C Clarke wrote a historic article in Wireless World describing a system that used satellites in geostationary orbit. Signals would be transmitted up to the satellite that would rebroadcast them back to the earth. -
1957 Sputnik 1 launched
On 4th October 1957 the USSR (Russia) launched the first satellite into orbit. The satellite was in a very low orbit which took 96 minutes to circle the earth. It only transmitted a bleep, but it was sufficient to prove that satellites could be successfully put into orbit. -
1962 Telstar launched
Several other satellites followed Sputnik. Some were launched by the Soviet Union, and others by the Americans. However the launch of Telstar proved to eb a major milestone in satellite development. On 23rd July 1962 it was used to make the first live transatlantic television transmissions. Signals from the USA were seen live in many homes around Europe, making communication shistory. -
1894 The coherer is popularised
The coherer, an item used to detect radio waves took many years to develop with the earliest observations dating back to 1850. The first person to use the idea of the coherer was a Frenchman named Edouard Branly. He discovered that the resistance of a glass tube filled with metal filings fell to a few hundred ohms when an electrical discharge occurred nearby. The filings could then be "de-cohered" by a sharp tap on the tube. These devices were effective in detecting the transmissions.