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.
Origins and developments Although development of the first radio wave communication system is attributed to Guglielmo Marconi, his was just the practical application of 80 years of scientific advancement in the field including the predictions of Michael Faraday, the theoretical work of James Clerk Maxwell, and the experimental demonstrations of Heinrich Rudolf Hertz.
1780–1784: George Adams notices sparks between charged and uncharged conductors when a Leyden jar was discharged nearby."The Opposite Directions of the Two Electricities Proved by the Appearances of the Electric Light in Vacuo", Lectures on Natural and Experimental Philosophy by the Late George Adams (volume 4), 1807, page 307. 1789–1791: Luigi Galvani notices a spark generated nearby causes a convulsion in a frog's leg being touched by a scalpel.Lindell, pp. 258–261 In different experiments, he notices contractions in frogs' legs caused by lightning and a luminous discharge from a charged Leyden jar that disappeared over time and was renewed whenever a spark occurred nearby. 1820: Hans Christian Ørsted discovers the relationship between electricity and magnetism in a very simple experiment. He demonstrates that a wire carrying a current was able to deflect a magnetized compass needle. 1831: Michael Faraday begins a series of experiments in which he discovers electromagnetic induction. The relation was mathematically modeled by Faraday's law, which subsequently becomes one of the four Maxwell equations. Faraday proposes that electromagnetic forces extended into the empty space around the conductor but does not complete his work involving that proposal. 1835: Peter Samuel Munk observes the permanent increase of the electrical conductivity of a mixture of loose metal filings in a glass tube with two metal plugs in it resulting from the passage of a discharge current of a Leyden jar through it. This is an early example of the coherer effect."Electrical Conductivity in Granular Media and Branly's Coherer: A Simple Experiment" by Eric Falcon and Bernard Castaing, February 2, 2008, page 1 (arxiv.org) 1842: Joseph Henry publishes his experimental results showing the oscillatory nature of the discharge in leyden jars and describes how a generated spark could magnetize a needle surrounded by a coil up to 220 feet away. He also describes how a lightning strike 8 miles away magnetized a needle surrounded by a coil, an effect that was most probably caused by radio waves. He considered both of these effects to be due to electromagnetic induction at the time.Albert E. Moyer (1994) Joseph Henry: The Rise of an American Scientist, Smithsonian Institution Press, pp. 172–176, 1852: Samuel Alfred Varley notices a remarkable fall in the resistance of masses of metallic filings under the action of atmospheric electrical discharges. 1864: James Clerk Maxwell predicts the existence of electromagnetic waves in his paper 'a dynamical theory of the electromagnetic field'.Lindell, p. 260 1871: Edwin Houston, while setting up a large sparking Ruhmkorff coil to be used in a demonstration, notices he can draw sparks from metal objects throughout the room. He attributes this to induction.Carlson (2003), p. 59 1875: While experimenting with an acoustic telegraph, Thomas Edison notices an electromagnet producing unusual sparks. He finds this strange sparking could be conducted 25 miles along telegraph wires and be detected a few feet from the wire. To prove it was not electromagnetic induction he set up an experiment where he shows sparks in a spark detector but no effect in a gold-leaf electroscope and a galvanometer along the same line. On 28 November 1875 he announces to the press what he terms a new "etheric force".Carlson (2003), pp. 57–58 December 1875: Edwin Houston, with the help of Elihu Thomson, conducts an improved version Edison's experiment at Central High School in Philadelphia, Pennsylvania using a Ruhmkorff coil and a spark detector. Thompson notices he can draw sparks from metal objects throughout the building and looks on the phenomenon as a possible new form of communication. Houston publishes his results, concluding that the phenomenon they and Edison produced was simply an induction phenomenon he had identified in 1871, claiming Edison was misidentifying a rapidly switching polarity.Carlson (2003), p. 60 1878: David E. Hughes notices that sparks generated by an induction balance cause noise in an improved telephone microphone he was developing. He rigs up a portable version of his receiver and, carrying it down a street, finds the sparking can be detected at some distance. 1879: German physicist Hermann von Helmholtz proposes the "Berlin Prize" for anyone who could experimentally prove a key aspect of Maxwell's electromagnetic theory thinking his star student, Heinrich Rudolf Hertz, could win the prize. Hertz declines working on the prize, seeing no way to produce a test apparatus. 1880: David Hughes demonstrates his discovery to the Royal Society, but is told it is merely induction. 1883: Irish physicist George Francis FitzGerald publishes a formula for the power radiated by a small loop antenna, showing it as proportional to the fourth power of the frequency. 1884: During his time as a lecturer in theoretical physics at Kiel University, Heinrich Hertz produces an analysis of Maxwell's equations showing they did have more validity than the then prevalent "action at a distance" theories. 1884: Temistocle Calzecchi-Onesti at Fermo in Italy discovers that metal filings between two brass plates clump together in reaction to electric sparks occurring at a distance. He thinks it could be used for detecting lightning. His little noticed paper is published in an Italian journal and he does not pursue the phenomenon further. (Considered an early type of "coherer"). 1885: Edison takes out a patent"Means for Transmitting Signals Electrically", U.S. Patent 465,971, issued December 29, 1891 to Thomas Edison (edison.rutgers.edu) on a system of wireless communication between ships via electrostatic induction through sea water. The system proves to be too short range to be practical.
1886 to 1888: After noticing how discharging an electric current into a coil produced a spark in a second nearby coil, Heinrich Hertz sees a way to build a test apparatus to solve von Helmholtz "Berlin Prize" problem. Hertz conducts a series of experiments that validates Maxwell's theory of electromagnetic radiation and proves that it can travel through free space (radio). He demonstrates the radiation has the properties of visible light, the properties of waves (now called Transverse waves), and discovers that the electromagnetic equations could be reformulated into a partial differential equation called the wave equation. Spring 1888: British physicist Sir Oliver Lodge conducts experiments that seem to show electromagnetic waves traveling along wires. He took this as a way to prove Maxwell's electromagnetic theory but learns of Hertz' published proofs at the same time. 1885 to 1892: Murray, Kentucky farmer Nathan Stubblefield conducts wireless transmissions some claim to be radio, but his devices seem to have worked by induction transmission rather than radio transmission. 1890: French physicist and inventor Edouard Branly does a thorough investigation of metal filings in an evacuated tube and how they are sensitive to electric sparks at a distance, an effect later to be called the coherer by Lodge. 1891: Irish physicist Frederick Thomas Trouton suggests using a fast rotating alternator as a wireless transmitter and that the new "Hertzian waves" could be used to replace light houses with "electric houses" that would operate in fog. February 1892: British chemist and physicist William Crookes publishes an article suggesting "Hertzian waves" (radio waves) could be, and he claimed already were being used in wireless telegraphy. July 1892: Elihu Thompson writes that "signalling or telegraphing for moderate distances without wires, and even through dense fog may be an accomplished fact soon". 1892: Branly's filing tube comes to light when it is described by Dr. Dawson Turner at a meeting of the British Association in Edinburgh. 1892: Scottish electrical engineer and astronomer George Forbes suggests Branly's filing tube may react in the presence of Hertzian waves. 1893: Nikola Tesla delivers a lecture "On Light and other High Frequency Phenomena" before the Franklin Institute in Philadelphia and the National Electric Light Association St Louis. Dubious of the existence air-borne radio waves,Carlson (2013), p. 127 he proposes a wireless lighting and wireless electric power transmission system that would work on air and ground conduction. He also notes the system could carry messages.Carlson (2013), pp. H-45, 301Christopher Cooper (2015) The Truth About Tesla: The Myth of the Lone Genius in the History of Innovation, Race Point Publishing, p. 165, Marc J. Seifer (1996) Wizard: The Life and Times of Nikola Tesla: Biography of a Genius, Citadel Press, p. 107, March 1893: American physicist Amos Dolbear predicts telegraphing without wires using "A beam of Hertzian rays" in Donahoe's Magazine. 1893: Physicist W. B. Croft exhibits Branly's experiments at a meeting of the Physical Society in London. It is unclear to Croft and others whether the filings in the Branly filing tube are reacting to sparks or the light from the sparks. George Minchin notices the [Branly] tube may be reacting to Hertzian waves the same way his solar cell does and writes the paper "The Action of Electromagnetic Radiation on Films containing Metallic Powders". These papers are read by Lodge who sees a way to build a much improved Herzian wave detector. 1 January 1894: Heinrich Rudolf Hertz dies. 1 June 1894: Oliver Lodge delivers a memorial lecture on Hertz where he demonstrates the optical properties of "Hertzian waves" (radio), including transmitting them over a short distance, using an improved version of Branly's filing tube, which Lodge has named the "coherer", as a detector. He also demonstrates controlling frequency by changing inductance and capacitance in his circuits. November 1894: Building on Lodge's published work, Indian physicist Jagdish Chandra Bose, sets up a small laboratory at Presidency Collage, Calcutta to explore radio microwave optics. December 1894: In Italy, Guglielmo Marconi conducts experiments in pursuit of building a wireless telegraph system based on Herzian waves (radio), demonstrated a radio transmitter and receiver to his mother, a set-up that made a bell ring on the other side of the room by pushing a telegraphic button on a bench. (radiomarconi.com) Retrieved on 12 July 2012.Antony Brown (1969) Great Ideas in Communications. D. White Co., p. 141 Financed by his family, over the next year he works on adapting experimental equipment into a radio wave telegraphic transmitter and receiver system that could work over long distances. This is considered to be the first development of a radio system specifically for communication. May 1895: After reading about Lodge's demonstrations, the Russian physicist Alexander Popov builds a "Hertzian wave" (radio wave) based lightning detector using a coherer. November 1895: Jagdish Chandra Bose sets up a demonstration of radio microwave at the Town Hall in Calcutta where he ignites gunpowder in a nearby room and rings a bell. 1896: Alexander Popov demonstrates the transmission of signals between buildings at the University of St. Petersburg.