1800s

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.

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.

1844

• Samuel Finley Breese Morse: 1791-1872

  By the age of 21, Samuel Morse showed an interest in electrical experimentation. A shipboard conversation in 1832 planted the seed for a method of telegraphy, and by 1835 the basic physical elements of a relay system were in place. A patent was issued in 1840, and the U.S. Congress gave him a grant for $30,000 to construct a line between Washington and Baltimore. The first message on this line was sent on May 24th, 1844. The "Morse Code" was invented by Morse, and his assistant Alfred Vail about 1840. The original code was simplified in 1851, and is called the 'Continental', or 'International' Morse code.

  Samuel F.B. Morse sends the first message of any distance by Telegraph - about 40 miles. The message -"What hath God wrought!" The wired Telegraph and Morse Code are the first long distance, instant communication system the world has known.

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'.

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.

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 termes a new "etheric force".
• December: 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 miss-identifying a rapidly switching polarity.

1878

• David E. Hughes notices that sparks generated by a induction balance causes 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

• Radio waves discovered.

1876

• Alexander Graham Bell: 1847-1922
  
  Bell was born in Scottland, and was home schooled until the age of ten. As a boy, his experiments with speech and sound reproduction led to a lifelong interest in the field. He was granted a patent in 1874 on a method of sending two or more telegraphic messages on the same wire, at the same time. The next year, as a result of an accident, words to the effect of "Watson - come here, I want you" were reproduced electronically by his 'telephone'. In August of 1876 the distance spanned by telephone was 8 miles, and 'long distance' became a reality by the end of that year, as he communicated over 143 miles. In 1880 Bell achieved the first wireless transmission of speech - using his invention -- the 'photophone' -- to transmit words on a beam of light. Alexander G. Bell demonstrates the telephone.

1888

• Heinrich Hertz detects and produces radio waves.

1892

• February: 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: Elihu Thompson writes that "signalling or telegraphing for moderate distances without wires, and even through dense fog may be an accomplished fact soon".
• Branly's filing tube comes to light when it is described by Dr. Dawson Turner at a meeting of the British Association in Edinburgh.
•  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. Tesla did not think air-born radio waves existed but saw wireless and electromagnetic phenomenon as a promising wireless lighting and power distribution system with communication as a side aspect.
• March: American physicist Amos Dolbear predicts telegraphing without wires using "A beam of Hertzian rays" in Donahoe's Magazine.
• 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.
• Irish physicist George Francis FitzGerald publishes a formula for the radiating power of electromagnetic waves from a loop antenna that seems to show these (radio) waves would only ever have a useful range of 1/2 mile, a value Oliver Lodge agrees with.

1892 to 1893

• Nikola Tesla wirelessly transmitted electromagnetic energy. He made the first public demonstration of radio in St. Louis in 1893.

1894

• January 1: Heinrich Rudolf Hertz dies.
• June 1: 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: In Calcutta the Indian physicist Jagdish Chandra Bose, building on Lodges published work, pursues the study of radio microwave optics and uses them to ignite gunpowder and rang a bell at a distance.
• December: 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. 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.
• Guglielmo Marconi: 1874-1937
  
  Probably the name associated most with the invention of radio, Marconi was certainly a visionary of what it could become. Born into a very well-to-do family in Bologna, Italy, Marconi first read of the pioneering work in radio in 1894, in an obituary of Heinrich Hertz. He was the first to realized the possibility of using this new technology as a form of communication, and he began his life work. Within the year he was ringing a bell by wireless control a few yards away, and by 1897 the distance spanned by his wireless was nearly 10 miles.
  
  Among his innovations were a greatly improved 'coherer' or detector, antenna work - including an earth ground which greatly increased his range, and the use of a high antenna. A vertical antenna with an earth ground is still referred to as a 'Marconi'. He also worked with directional antenna's.

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. Unfortunately they were not impressed, and as a result Marconi moved to England.

• 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 of a spark transmitter. The idea was popularised by Oliver Lodge, especially as a result of a lecture he gave in 1894.

 1895

• Marconi succeeds in signaling across the family estate by radio - a distance of about 1.2 miles.
• May: After reading about Lodge's demonstrations, the Russian physicist Alexander Popov builds a "Hertzian wave" (radio wave) based lightning detector using a coherer.

1896

•  Marconi transports his wireless invention to England. Upon entry to the country, nervous customs officials smash his apparatus under suspicion that it may be part of an Italian anarchist plot.
• Nikola Tesla introduces the use of a rotary gap for his spark transmitter.
• Marconi takes out patents in England for 'wireless telegraphy'. At the age of 22 he filed for his first patent (#7777) for a system of radio communication. Five years later he succeeded in signaling across the Atlantic Ocean. Guglielmo Marconi reads about Heinrich Hertz's discovery of electro-magnetic waves.
• Alexander Popov demonstrates the transmission of signals between building at the University of St. Petersburg.
• Marconi was awarded a patent for radio with British Patent 12039, Improvements in Transmitting Electrical Impulses and Signals and in Apparatus There-for. This is the initial patent for radio based wireless telegraphy.
• Bose goes to London on a lecture tour and meets Marconi, who was conducting wireless experiments for the British post office.

1897

• The Marconi Company is formed in England.
• Marconi established the Wireless Telegraph and Signal Company.
• 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. Accordingly 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.
• In the U.S. during 1897, Tesla applies for several wireless power patents. Those two patents were issued in early 1900.
• Although Australia's first officially recognised broadcast was made in 1906, some sources claim that there were transmissions in Australia in 1897, either conducted solely by Professor William Henry Bragg of Adelaide University or by Prof. Bragg in conjunction with G.W. Selby of Melbourne.

1898

• Marconi installs the worlds first commercial radio service on Rathlin Island off the coast of Ireland.
• Marconi opened the first radio factory, on Hall Street, Chelmsford, England, employing around 50 people.

1899

• Marconi installs wireless equipment on three British battleships.
• Nathan B. Stubblefield reportedly transmits voice messages by wireless.
• Marconi sends radio messages across the English Channel. 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.
• Marconi arrives in New York with his wireless equipment to issue radio reports on a yacht race.
• Bose announced his invention of the "iron-mercury-iron coherer with telephone detector" in a paper presented at Royal Society, London.
• Tesla experiments with wireless power in Colorado Springs. He listens to static from thunderstorms trying to determine values for what he believes is a native electrical charge and frequency of the Earth. Using sensitive electromagnetic receivers he picks up repeating signals he thinks may be from beings on another planet. An alternative explanation is that Tesla may have heard Marconi's wireless telegraphy demonstrations in Europe.

 Sources: Radio History
Radio Timeline
Timeline of Radio