Guglielmo Giovanni Maria Marconi, 1st Marquis of Marconi was an Italian inventor and electrical engineer, known for his creation of a practical radio wave-based wireless telegraph system. This led to Marconi being credited as the inventor of radio, and he shared the 1909 Nobel Prize in Physics with Karl Ferdinand Braun "in recognition of their contributions to the development of wireless telegraphy".
The early history of radio is the history of technology that produces and uses radio instruments that use radio waves. Within the timeline of radio, many people contributed theory and inventions in what became radio. Radio development began as "wireless telegraphy". Later radio history increasingly involves matters of broadcasting.
Wireless telegraphy or radiotelegraphy is transmission of text messages by radio waves, analogous to electrical telegraphy using cables. Before about 1910, the term wireless telegraphy was also used for other experimental technologies for transmitting telegraph signals without wires. In radiotelegraphy, information is transmitted by pulses of radio waves of two different lengths called "dots" and "dashes", which spell out text messages, usually in Morse code. In a manual system, the sending operator taps on a switch called a telegraph key which turns the transmitter on and off, producing the pulses of radio waves. At the receiver the pulses are audible in the receiver's speaker as beeps, which are translated back to text by an operator who knows Morse code.
In telecommunication, especially radio communication, spread spectrum designates techniques by which a signal generated with a particular bandwidth is deliberately spread in the frequency domain, resulting in a signal with a wider bandwidth. Spread-spectrum techniques are used for the establishment of secure communications, increasing resistance to natural interference, noise, and jamming, to prevent detection, to limit power flux density, and to enable multiple-access communications.
Frequency-hopping spread spectrum (FHSS) is a method of transmitting radio signals by rapidly changing the carrier frequency among many frequencies occupying a large spectral band. The changes are controlled by a code known to both transmitter and receiver. FHSS is used to avoid interference, to prevent eavesdropping, and to enable code-division multiple access (CDMA) communications.
The coherer was a primitive form of radio signal detector used in the first radio receivers during the wireless telegraphy era at the beginning of the 20th century. Its use in radio was based on the 1890 findings of French physicist Édouard Branly and adapted by other physicists and inventors over the next ten years. The device consists of a tube or capsule containing two electrodes spaced a small distance apart with loose metal filings in the space between. When a radio frequency signal is applied to the device, the metal particles would cling together or "cohere", reducing the initial high resistance of the device, thereby allowing a much greater direct current to flow through it. In a receiver, the current would activate a bell, or a Morse paper tape recorder to make a record of the received signal. The metal filings in the coherer remained conductive after the signal (pulse) ended so that the coherer had to be "decohered" by tapping it with a clapper actuated by an electromagnet, each time a signal was received, thereby restoring the coherer to its original state. Coherers remained in widespread use until about 1907, when they were replaced by more sensitive electrolytic and crystal detectors.
The Audion was an electronic detecting or amplifying vacuum tube invented by American electrical engineer Lee de Forest in 1906. It was the first triode, consisting of an evacuated glass tube containing three electrodes: a heated filament, a grid, and a plate. It is important in the history of technology because it was the first widely used electronic device which could amplify. A low power signal at the grid could control much more power in the plate circuit.
Greenleaf Whittier Pickard was a United States radio pioneer. Pickard was a researcher in the early days of wireless. While not the earliest discoverer of the rectifying properties of contact between certain solid materials, he was largely responsible and most famous for the development of the crystal detector, the earliest type of diode detector. The crystal detector was the central component in many early radio receivers from around 1906 until about 1920. Pickard also experimented with antennas, radio wave propagation and noise suppression. On August 30, 1906 he filed a patent for a silicon crystal detector, which was granted on November 20, 1906. On June 10, 1907 he filed a patent for a Magnetic Aerial which was granted on January 21, 1908. Pickard's loop antenna had directional properties that could be used to reduce interference to the intended wireless communications. On June 21, 1911 he filed a patent on a crystal detector incorporating a springy low inertia wire of about 24 gauge formed with a loop or helix and pointed to make contact with the crystal. Crystal detectors incorporating this construction would become the most widely used and popularly known by the term cat whisker detector. This patent was granted on July 21, 1914. Greenleaf Whittier Pickard was named after his great-uncle, the American Quaker John Greenleaf Whittier (1807-1892). Pickard was president of the Institute of Radio Engineers in 1913.
Amos Emerson Dolbear was an American physicist and inventor. Dolbear researched electrical spark conversion into sound waves and electrical impulses. He was a professor at University of Kentucky in Lexington from 1868 until 1874. In 1874 he became the chair of the physics department at Tufts University in Medford, Massachusetts. He is known for his 1882 invention of a system for transmitting telegraph signals without wires. In 1899 his patent for it was purchased in an unsuccessful attempt to interfere with Guglielmo Marconi's wireless telegraphy patents in the United States.
A spark-gap transmitter is an obsolete type of radio transmitter which generates radio waves by means of an electric spark. Spark-gap transmitters were the first type of radio transmitter, and were the main type used during the wireless telegraphy or "spark" era, the first three decades of radio, from 1887 to the end of World War I. German physicist Heinrich Hertz built the first experimental spark-gap transmitters in 1887, with which he proved the existence of radio waves and studied their properties.
John Stone Stone was an American mathematician, physicist and inventor. He initially worked in telephone research, followed by influential work developing early radio technology, where he was especially known for improvements in tuning. Despite his often advanced designs, the Stone Telegraph and Telephone Company failed in 1908, and he spent the remainder of his career as an engineering consultant.
Jozef Murgaš was a Slovak inventor, architect, botanist, painter and Roman Catholic priest. He contributed to radio development, which at the time was commonly known as "wireless telegraphy".
The invention of radio communication was preceded by many decades of establishing theoretical underpinnings, discovery and experimental investigation of radio waves, and engineering and technical developments related to their transmission and detection. These developments allowed Guglielmo Marconi to turn radio waves into a wireless communication system.
The timeline of radio lists within the history of radio, the technology and events that produced instruments that use radio waves and activities that people undertook. Later, the history is dominated by programming and contents, which is closer to general history.
The Fleming valve, also called the Fleming oscillation valve, was a thermionic valve or vacuum tube invented in 1904 by English physicist John Ambrose Fleming as a detector for early radio receivers used in electromagnetic wireless telegraphy. It was the first practical vacuum tube and the first thermionic diode, a vacuum tube whose purpose is to conduct current in one direction and block current flowing in the opposite direction. The thermionic diode was later widely used as a rectifier — a device which converts alternating current (AC) into direct current (DC) — in the power supplies of a wide range of electronic devices, until beginning to be replaced by the selenium rectifier in the early 1930s and almost completely replaced by the semiconductor diode in the 1960s. The Fleming valve was the forerunner of all vacuum tubes, which dominated electronics for 50 years. The IEEE has described it as "one of the most important developments in the history of electronics", and it is on the List of IEEE Milestones for electrical engineering.
Archie Frederick Collins, who generally went by A. Frederick Collins, was a prominent early American experimenter in wireless telephony and prolific author of books and articles covering a wide range of scientific and technical subjects. His reputation was tarnished in 1913 when he was convicted of mail fraud related to stock promotion. However, after serving a year in prison, he returned to writing, including, beginning in 1922, The Radio Amateur's Handbook, which continued to be updated and published until the mid-1980s.
The World Wireless System was a turn of the 20th century proposed telecommunications and electrical power delivery system designed by inventor Nikola Tesla based on his theories of using Earth and its atmosphere as electrical conductors. He claimed this system would allow for "the transmission of electric energy without wires" on a global scale as well as point-to-point wireless telecommunications and broadcasting. He made public statements citing two related methods to accomplish this from the mid-1890s on. By the end of 1900 he had convinced banker J. P. Morgan to finance construction of a wireless station based on his ideas intended to transmit messages across the Atlantic to England and to ships at sea. His decision to change the design to include wireless power transmission to better compete with Guglielmo Marconi's new radio based telegraph system was met with Morgan's refusal to fund the changes. The project was abandoned in 1906, never to become operational.
Homer Clyde Snook was an American electrical engineer and inventor. He developed the Snook apparatus, the first interrupterless device produced for X-ray work.