The identity of the original inventor of radio, at the time called wireless telegraphy, is contentious.
In 1893 in St. Louis, Missouri, Nikola Tesla made the first public demonstration of radio communication. Addressing the Franklin Institute in Philadelphia and the National Electric Light Association, he described and demonstrated in detail the principles of radio communication. The apparatus that he used contained all the elements that were incorporated into radio systems before the development of the vacuum tube.
In 1894 British physicist Sir Oliver Lodge demonstrated the possibility of signalling using radio waves using a detecting device called a coherer, a tube filled with iron filings which had been invented by Temistocle Calzecchi-Onesti at Fermo in Italy in 1884. Edouard Branly of France and Alexander Popov of Russia later produced improved versions of the coherer. Popov, who developed a practical communication system based on the coherer, is often considered by his own countrymen to have been the inventor of radio.
In 1896 Guglielmo Marconi was awarded what is sometimes recognised as the world’s first patent for radio with British Patent 12039, Improvements in transmitting electrical impulses and signals and in apparatus there-for.
In 1897 in the USA, some key developments in radio’s early history were created and patented by Nikola Tesla. However the US Patent Office reversed its decision in 1904, awarding Guglielmo Marconi a patent for the invention of radio, possibly influenced by Marconi’s financial backers in the States, who included Thomas Edison and Andrew Carnegie. In 1909 Marconi, with Karl Ferdinand Braun, was also awarded the Nobel Prize in Physics for “contributions to the development of wireless telegraphy”.
However, Tesla’s patent (number 645576) was reinstated in 1943 by the US Supreme Court, shortly after his death. This decision was based on the fact that there was prior work existing before the establishment of Marconi’s patent. Some believe it was apparently made for financal reasons, to allow the US Government to avoid having to the pay damages that were being claimed by the Marconi Company for use of its patents during World War I.
Claims have also been made that Nathan Stubblefield invented radio before either Tesla or Marconi, but his device seems to have worked by induction transmission rather than radio transmission. Marconi opened the world’s first “wireless” factory in Hall Street, Chelmsford, England in 1898, employing around 50 people. The next great invention was the vacuum tube detector, invented by a team of Westinghouse engineers.
On Christmas Eve, 1906, using his heterodyne principle, Reginald Fessenden transmitted the first radio audio broadcast in history from Brant Rock Station, Massachusetts. Ships at sea heard a broadcast that included Fessenden playing the song O Holy Night on the violin and reading a passage from the Bible. The world’s first regular wireless broadcasts for entertainment commenced in 1922 from the Marconi Research Centre at Writtle near Chelmsford, England, which was also the location of the world’s first “wireless” factory.
Early radios ran the entire power of the transmitter through a carbon microphone. In the 1920s, amplifying vacuum tubes revolutionized both radio receivers and radio transmitters.
Developments in the 20th century:
- As a matter of course, aircraft used commercial AM radio stations for navigation. This continued through the early 1960s when VOR systems finally became widespread.
- In the early 1930s, single sideband and frequency modulation were invented by amateur radio operators. By the end of the decade, they were established commercial modes.
- In 1948, radio became visible as television.
- In 1960, Sony introduced the first transistorized radio, small enough to fit in a vest pocket, and able to be powered by a small battery. It was reliable, because there were no tubes to burn out. Over the next twenty years, transistors displaced tubes almost completely except for very high power, or very high frequency.
- In 1963 color television was commercially transmitted, and the first (radio) communication satellite was launched.
- In the late 1960s, the U.S. long-distance telephone network began to convert to a digital network, employing digital radios for many of its links.
- In the 1970s, LORAN became the premier radio navigation system. Soon, the U.S. Navy experimented with satellite navigation, culminating in the invention and launch of the GPS constellation in 1987.
- In the early 1990s, amateur radio experimenters began to use personal computers with audio cards to process radio signals. In 1994, the U.S. Army and DARPA launched an aggressive, successful project to construct a software radio that could become a different radio on the fly by changing software.