Invention of radio

"Great Radio Controversy" redirects here. For the album by the band Tesla, see The Great Radio Controversy.

Many people were involved in the invention of radio as we know it today. Experimental work on the connection between electricity and magnetism began around 1820 with the work of Hans Christian Ørsted, and continued with the work of André-Marie Ampère, Joseph Henry, and Michael Faraday. These investigations culminated in a theory of electromagnetism developed by James Clerk Maxwell, which predicted the existence of electromagnetic waves.

After Maxwell's theory was published many people experimented with diverse forms of wireless communication. The first intentional transmission and reception of a signal by means of electromagnetic waves was demonstrated by David Edward Hughes around 1880, although some observers were not convinced they were electromagnetic at the time. The first conclusive demonstration of the existence of electromagnetic waves was performed by Heinrich Rudolf Hertz, and described in papers published in 1887 and 1890. Hertz famously considered these results as being of little practical value.

After Hertz's work many people were involved in further development of the electronic components and methods used for communication via electromagnetic waves. Others, notably Guglielmo Marconi, were concerned with practical improvements and the commercial application of radio to wireless telegraphy. Later on Reginald A. Fessenden became the first to send an audio signal by means of electromagnetic waves.

Wireless signalling methods

Several different electrical, magnetic or electromagnetic physical phenomena can be used to transmit signals over a distance without intervening wires. The various methods for wireless signal transmissions include:

• Electrical conduction through the ground, or through water.
• Magnetic induction
• Capacitive coupling
• Electromagnetic radiation

All these physical phenomena, as well as various other ideas such as conduction through air, were tested for the purpose of communication. Early researchers may not have understood or disclosed which physical effects were responsible for transmitting signals. Early experiments used the existing theories of the movement of charged particles through an electrical conductor. There was no theory of electromagnetic wave propagation to guide experiments before Maxwell's treatise and its verification by Hertz and others.

Capacitive and inductive coupling systems today are used only for short-range special purpose systems. The physical phenomenon used today for long-distance wireless communications involves the use of modulated electromagnetic waves, which is radio.

Theory of electromagnetism

Main article: History of electromagnetism

Experiments and Theory

Joseph Henry Michael Faraday Hans Christian Ørsted

Various scientists proposed that electricity and magnetism were linked. Around 1800 Alessandro Volta developed the first means of producing an electrical current. In 1802 Gian Domenico Romagnosi may have suggested a relationship between electricity and magnetism but his reports went unnoticed. In 1820 Hans Christian Ørsted performed a simple and today widely known experiment on electric current and magnetism. He demonstrated that a wire carrying a current could deflect a magnetized compass needle. Ørsted's work influenced André-Marie Ampère to produce a theory of electromagnetism.

Several scientists speculated that light might be connected with electricity or magnetism. Around 1830 Francesco Zantedeschi suggested a connection between light, electricity, and magnetism.

In 1831, Michael Faraday began a series of experiments in which he discovered electromagnetic induction. The relation was mathematically modelled by Faraday's law, which subsequently became one of the four Maxwell equations. Faraday proposed that electromagnetic forces extended into the empty space around the conductor, but did not complete his work involving that proposal. In 1846 Michael Faraday speculated that light was a wave disturbance in a force field".

In 1832 Joseph Henry performed experiments detecting inductive magnetic effects over a distance of 200 feet (61 m). He was the first (1838–42) to produce high frequency AC electrical oscillations, and to point out and experimentally demonstrate that the discharge of a condenser under certain conditions is oscillatory, or, as he puts it, consists "of a principal discharge in one direction and then several reflex actions backward and forward, each more feeble than the preceding until equilibrium is attained". This view was also later adopted by Helmholtz, but the mathematical demonstration of this fact was first given by Lord Kelvin in his paper on "Transient Electric Currents".

Maxwell and the theoretical prediction of electromagnetic waves

James Clark Maxwell

Between 1861 and 1865, based on the earlier experimental work of Faraday and other scientists, and on his own modification to Ampere's law James Clerk Maxwell, developed his theory of electromagnetism, which predicted the existence of electromagnetic waves. In 1873 Maxwell described the theoretical basis of the propagation of electromagnetic waves in his paper to the Royal Society, "A Dynamical Theory of the Electromagnetic Field." This theory united all previously unrelated observations, experiments and equations of electricity, magnetism, and optics into a consistent theory. His set of equations—Maxwell's equations—demonstrated that electricity, magnetism, and light are all manifestations of the same phenomenon, the electromagnetic field. Subsequently, all other classic laws or equations of these disciplines were special cases of Maxwell's equations. Maxwell's work in electromagnetism has been called the "second great unification in physics".

Although Maxwell did not transmit or receive radio waves his equations still remain the basis of all radio design.

Early attempts at wireless communication

Wireless telegraphy

Before the discovery electromagnetic waves and the development of radio communication there were many wireless telegraph systems proposed or tried out.

In April 1872 William Henry Ward received U.S. patent 126,356 for a wireless telegraphy system where he theorized that convection currents in the atmosphere could carry signals like a telegraph wire. A few months after Ward received his patent, Mahlon Loomis of West Virginia received U.S. patent 129,971 for a "wireless telegraph" in July 1872. This claimed to utilize atmospheric electricity to eliminate the overhead wire used by the existing telegraph systems. It did not contain diagrams or specific methods and it did not refer to or incorporate any known scientific theory. It is similar to William Henry Ward's patent.

Edison's U.S. patent 465,971

Towards the end of 1875, while experimenting with the telegraph, Thomas Edison noted a phenomenon that he termed "etheric force", announcing it to the press on November 28. He abandoned this research when Elihu Thomson, among others, ridiculed the idea. The idea was not based on the electromagnetic waves described by Maxwell. In 1885, Edison took out U.S. patent 465,971 on a system of electrical wireless communication between ships (which later he sold to the Marconi Company). The patent, however, was based on the mutual-inductively coupled or magnetically coupled communication.

An alternative form of Wireless telephony is recorded in four patents for the photophone, invented jointly by Alexander Graham Bell and Charles Sumner Tainter in 1880. The photophone allowed for the transmission of sound on a beam of light, and on June 3, 1880 Bell and Tainter transmitted the world's first wireless telephone message on their newly invented form of telecommunication.

Nathan Stubblefield claimed to have developed radio between 1885 and 1892, but his devices seemed to have worked by induction transmission rather than radio transmission.

"The Wireless Telephone" U S Patent Office in Washington, DC

Experiments and proposals

Berend Wilhelm Feddersen (German physicist) in 1859, as a private scholar in Leipzig, succeeded in experiments with the Leyden jar to prove that electric sparks were composed of damped oscillations. He realized that they arise from a coil, capacitor and resistor existing electrical circuit oscillations.

In 1870 the German physicist Wilhelm von Bezold discovered and demonstrated the fact that the advancing and reflected oscillations produced in conductors by a capacitor discharge gave rise to interference phenomena. Professors Elihu Thomson and E. J. Houston in 1876 made a number of experiments and observations on high frequency oscillatory discharges. In 1883 George FitzGerald suggested at a British Association meeting that electromagnetic waves could be generated by the discharge of a capacitor, but the suggestion was not followed up, possibly because no means was known for detecting the waves.

Hughes

In 1879, David Edward Hughes discovered that sparks would generate a radio signal that could be detected by listening to a telephone receiver connected to his new microphone design. He developed his spark-gap transmitter and receiver into a working communication system using trial and error experiments, until eventually he could demonstrate the ability to send and receive Morse code signals out to a range limited to 500 yards (460 m). Prominent attendees of the demonstrations were Sir William Crookes Sir William Henry Preece, William Grylls Adams, and James Dewar.

Hughes demonstrated his technology to representatives of the Royal Society in February 1880, but they were not convinced that it was truly radio, and not merely induction. Hughes' work was not published until a brief mention of it in 1892, and a full magazine article was written about it in 1899.

Hughes "abundantly proved his claim to have been the first to transmit actual signals..." "Hughes's experiments of 1879 were virtually a discovery of Hertzian waves before Hertz, of the coherer before Branly, and of wireless telegraphy before Marconi and others."

Hughes discovered that his microphone design exhibited unusual properties in the presence of radio signals. He experimented with the discovery, and described his creation of both the device later known as a "coherer", and an improved semiconductor carbon and steel point-contact rectifying diode, which he also called a "coherer". The point-contact diode version of the device is now known as a crystal radio detector, and was the key component of his sensitive crystal radio receiver.

Point-contact diodes had been independently discovered by other scientists. They were later studied and described in detail by J.C. Bose, in his research on their use in radio receivers. John Ambrose Fleming earned a Hughes Medal after he improved the Hughes diode receiver component with his invention of a vacuum tube diode, which could be operated more reliably than the semiconductor technology of the time. Fleming's U.S. patent for the vacuum tube rectifier diode was invalidated due to the prior art of the other diode researchers who preceded him.

Elihu Thomson recognized the Hughes claim to be the first to transmit radio. Hughes himself said "with characteristic modesty" that Hertz's experiments were "far more conclusive than mine", and that Marconi's "efforts at demonstration merit the success he has received...[and] the world will be right in placing his name on the highest pinnacle, in relation to aerial electric telegraphy".

Hertz experimentally verifies Maxwell's theory

Heinrich Hertz

Between 1886 and 1888 Heinrich Rudolf Hertz studied Maxwell's theory and conducted experiments that validated it through more rigorous scientific techniques than Hughes had used. He engineered a method of detecting spark-gap radio waves by observing that another unpowered spark-gap, acting as an antenna, would absorb the radio energy and convert it back into an electric spark. Hertz published his results in a series of papers between 1887 and 1890, and again in complete book form in 1893.

The first of the papers published, "On Very Rapid Electric Oscillations", gives an account of the chronological course of his investigation, as far as it was carried out up to the end of the year 1886 and the beginning of 1887.

For the first time, electromagnetic radio waves ("Hertzian waves") were intentionally and unequivocally proven to have been transmitted through free space by a spark-gap device, and detected over a short distance.

1887 experimental setup of Hertz's apparatus.

Hertz was able to have some control over the frequencies of his radiated waves by altering the inductance and capacitance of his transmitting and receiving antennas. He focused the electromagnetic waves using a corner reflector and a parabolic reflector, to demonstrate that radio behaved the same as light, as Maxwell's electromagnetic theory had predicted more than 20 years earlier. He demonstrated that radio had all the properties of waves, and discovered that the electromagnetic equations could be reformulated into a partial differential equation called the wave equation.

Hertz did not devise a system for practical utilization of electromagnetic waves, nor did he describe any potential applications of the technology. Hertz was asked by his students at the University of Bonn what use there might be for these waves. He replied, “It's of no use whatsoever. This is just an experiment that proves Maestro Maxwell was right, we just have these mysterious electromagnetic waves that we cannot see with the naked eye. But they are there.”

Hertz died in 1894, and the art of radio wave communication was left to others to implement into a practical form. After Hertz's experiments, Sir William Crookes published an article in 1892 with his thoughts on possibility of wireless communication based on the research of Lodge and Hertz, and the American physicist Amos Emerson Dolbear brought similar attention to the idea.

Wireless Telegraphy

Branly

In 1890, Édouard Branly demonstrated what he later called the "radio-conductor," which Lodge in 1893 named the coherer, the first sensitive device for detecting radio waves. Shortly after the experiments of Hertz, Branly discovered that loose metal filings, which in a normal state have a high electrical resistance, lose this resistance in the presence of electric oscillations and become practically conductors of electricity. This Branly showed by placing metal filings in a glass box or tube, and making them part of an ordinary electric circuit. According to the common explanation, when electric waves are set up in the neighborhood of this circuit, electromotive forces are generated in it which appear to bring the filings more closely together, that is, to cohere, and thus their electrical resistance decreases, from which cause this piece of apparatus was termed by Sir Oliver Lodge a coherer. Hence the receiving instrument, which may be a telegraph relay, that normally would not indicate any sign of current from the small battery, can be operated when electric oscillations are set up. Branly further found that when the filings had once cohered they retained their low resistance until shaken apart, for instance, by tapping on the tube. The coherer, however, was not sensitive enough to be used reliably as radio developed.

Tesla

In the early 1890s Nikola Tesla began research into high frequency electricity. During his visit to the Paris Exposition Universelle in 1889 Tesla learned of Hertz's experiments with electromagnetic waves using coils and spark gaps and proceeded to duplicate those experiments. Tesla came to the conclusion that Maxwell, Lodge, and Hertz were wrong in their findings that air born electromagnetic waves (radio waves) were being transmitted and instead attributed it to what he called “electrostatic thrusts”, with the real signals being conducted by Earth currents.

In 1891 he developed various alternator apparatus that produced 15,000 cycles per second and developed his own very large air gaped coil, known now as a Tesla coil. Tesla's primary interest in wireless phenomenon was as a power distribution system. By 1892 he was delivering lectures on high potential/high frequency alternate currents" and went on to demonstrate "wireless lighting" in 1893 including lighting Geissler tubes wirelessly. Tesla proposed this wireless technology could be developed into a system for the telecommunication of information.

Tesla (like many scientists of that time) thought, even if radio waves existed, they would probably only travel in straight lines making them useless for long range transmission. His laboratory work and later large scale experiments at Colorado Springs led him to the conclusion that a world wide wireless system would have to use the Earth itself (via injecting very large amounts of electrical current into the ground) as the means to conduct the signal to overcome this limitation. He went on to try to implement his ideas of power transmission and wireless telecommunication in his very large but unsuccessful Wardenclyffe Tower project.

Tesla also developed a wireless remote controlled boat with secure communication between transmitter and receiver. which he demonstrated in 1898.

de Moura

Roberto Landell de Moura, a Brazilian priest and scientist, conducted experiments in wireless in Campinas and São Paulo (1892–1893). According to the newspaper Jornal do Comercio (June 10, 1900), he conducted his first public experiment on June 3, 1900, in front of journalists and the General Consul of Great Britain, in the City of São Paulo, Brazil, reaching a distance of approximately 8 km from Alto de Santana to Paulista Avenue. One year after the above experiment in public, he received his first patent from the Brazilian government. It was described as "equipment for the purpose of phonetic transmissions through space, land and water elements at a distance with or without the use of wires". De Moura later obtained several patents on wireless technology. Four months later, he left Brazil for the United States of America with the intent of patenting the machine in the U S, eventually obtaining three patents: "The Wave Transmitter" (October 11, 1904), "The Wireless Telephone", and the "Wireless Telegraph", both dated November 22, 1904.

Lodge

One of the first investigators to notice and measure stationary waves on wires produced by direct coupling (resonance) with the coatings of a Leyden jar was Sir Oliver Lodge, entitled "Experiments On The Discharge Of Leyden Jars" (1891). On June 1, 1894, Oliver Lodge at the Royal Institution lectures, delivered "The Work of Hertz and Some of His Successors". Lodge performed a transmission on August 14, 1894. Lodge did this at a meeting of the British Association for the Advancement of Science at Oxford University. Also in 1894, Lodge would state that Alexander Muirhead clearly foresaw the telegraphic importance of the transmission of transverse Hertzian waves. A convenient method of establishing stationary electric waves on wires is one which generally attribute to Ernst Lecher, and call the Lecher arrangement. As a matter of fact, it originated with Lodge and Hertz, whilst Edouard Sarasin and Lucien de la Rive gave it an improved form.

On that day in August 1894, Lodge demonstrated the reception of Morse code signalling via radio waves using a "coherer". He later improved Branly's coherer by adding a "trembler" which dislodged clumped filings, thus restoring the device's sensitivity. In August 1898 he got U.S. patent 609,154, "Electric Telegraphy", that made wireless signals using Ruhmkorff coils or Tesla coils for the transmitter and a Branly coherer for the detector. This patent utilized the concept of "syntonic" tuning. In 1912 Lodge sold the patent to Marconi.

In 1894 Lodge showed that the Branly coherer could be employed to transmit telegraphic signals, and in order that the filings should not remain "cohered" after the cessation of the electric oscillations, he devised an electro-mechanical "tapper" on the principle of the ordinary "buzzer," or electric door-bell, the hammer of which was caused to tap the glass tube as long as the electric oscillations continued. The filings thus virtually take the place of a key in the ordinary telegraph circuit. In the normal state the key is open; in the presence of electrical oscillations the key is closed. Thus, by opening and closing the key for a longer or shorter period, signals corresponding to dots and dashes may be produced. In other words, by setting up electric oscillations for periods of time corresponding to dots and dashes, messages may be transmitted from the sending station, and if, at the receiving station, a recording instrument (controlled by the coherer), such as the ordinary Morse register, be provided, a record of the message in dots and dashes may be obtained. Dr. Lodge in fact used a tapper operated continuously by clockwork.

In 1894, with the help of the Branly filings tube, Lodge gave a couple of demonstrations, one in June at the Royal Institution at Oxford and one in August at Oxford, to the British Association, using Hertz oscillators for transmitting signals, using a Morse key in connection with the sending coil, and a Thomson marine galvanometer for receiving them—sending the signals from one room to another through walls, and so on. Lodge sent them also across the quadrangle of Liverpool College, but he applied very small power and did not try for big distances. At that time Dr. Alexander Muirhead was struck with its applicability to practical telegraphy, and when in 1896 Sir William Preece told the British Association meeting (as it happened in his laboratory) at Liverpool that an Italian gentleman (at that time unknown) was interesting the Post Office in a secret box, Lodge knew practically what the box must contain, and immediately afterwards (the same day) he showed to a few friends a Morse tape instrument, very roughly working on that plan. Mr. Marconi and Sir William Preece together interested the whole world in the subject; great power was applied to the sender, and the matter became of financial importance. However, the American Patent Office gave Lodge a telegraphic patent based on his work, as published in 1894, after proof that this book had reached America in or before 1895.

J.C.Bose

In November 1894, the Indian physicist, Jagadish Chandra Bose, demonstrated publicly the use of radio waves in Calcutta, but he was not interested in patenting his work. Bose ignited gunpowder and rang a bell at a distance using electromagnetic waves, confirming that communication signals can be sent without using wires. He sent and received radio waves over distance but did not commercially exploit this achievement.

Bose demonstrated the ability of the electric rays to travel from the lecture room, and through an intervening room and passage, to a third room 75 feet (23 m) distant from the radiator, thus passing through three solid walls on the way, as well as the body of the chairman (who happened to be the Lieutenant-Governor). The receiver at this distance still had energy enough to make a contact which set a bell ringing, discharged a pistol, and exploded a miniature mine. To get this result from his small radiator, Bose set up an apparatus which curiously anticipated the lofty 'antennae' of modern wireless telegraphy— a circular metal plate at the top of a pole, 20 feet (6.1 m) high, being put in connection with the radiator and a similar one with the receiving apparatus.

The form of 'Coherer' devised by Professor Bose, and described by him at the end of his paper 'On a new Electro Polariscope' allowed for the sensibility and range to appear to leave little to be desired at the time. In 1896, the Daily Chronicle of England reported on his UHF experiments: "The inventor (J.C. Bose) has transmitted signals to a distance of nearly a mile and herein lies the first and obvious and exceedingly valuable application of this new theoretical marvel."

After Bose's Friday Evening Discourses at the Royal Institution, The Electric Engineer expressed 'surprise that no secret was at any time made as to its construction, so that it has been open to all the world to adopt it for practical and possibly money-making purposes.' Bose was sometimes, and not unnaturally, criticised as unpractical for making no profit from his inventions.

In 1899, Bose announced the development of an "iron-mercury-iron coherer with telephone detector" in a paper presented at the Royal Society, London. Later he received U.S. patent 755,840, "Detector for electrical disturbances" (1904), for a specific electromagnetic receiver. Bose would continue research and made other contributuions to the development of radio.

Practical and commercial development of wireless telegraphy

Main article: History of broadcasting

Popov

During the Chicago World's Columbian Exhibition and the Third International Electrical Congress, Alexander Stepanovich Popov of Kronstadt, Russia was a representative of the Russian Torpedo School. Afterward, he worked on his wireless designs. Popov conducted experiments along the lines of Hertz's research. In 1894-95 he built his first radio receiver, an improved version of coherer-based design by Oliver Lodge. In 1895, he built a coherer. Popov constructed a filings coherer, one form of which was used in some surveying experiments by the Russian government. He used early in 1895, the coherer auto-tapping mechanism, and substituted for the galvanometer an ordinary telegraphic relay. He operated this apparatus at a distance by means of a large radiator. One terminal of his coherer was connected to a conductor fastened to a mast about 30 ft. high on the top of the Institute building and the other terminal of the coherer was grounded.

Popov presented his radio receiver to the Russian Physical and Chemical Society on May 7, 1895 — the day has been celebrated in the Russian Federation as "Radio Day". On this day, Popov performed a public demonstration of transmission and reception of radio waves used for communication at the Russian Physical and Chemical Society, using his coherer. The paper on his findings was published the same year (December 15, 1895). Popov had recorded, at the end of 1895, that he was hoping for distant signaling with radio waves. He did not apply for a patent for this invention. Popov's early experiments were transmissions of only 600 yards (550 m). Popov was the first to develop a practical communication system based on the coherer, and is usually considered by the Russians to have been the inventor of radio.

In 1895-96 Popov and others utilized the coherer to show the existence of atmospheric electricity, using for the purpose a vertical wire attached to the coherer. On March 24, 1896, Popov demonstrated in public the transmission of radio waves, between different campus buildings, to the Saint Petersburg Physical Society. Per other accounts, however, Popov achieved these results only in December 1897—that is, after publication of Marconi's patent. In 1898 his signal was received 6 miles (9.7 km) away, and in 1899 130 miles (210 km) away.

His receiver proved to be able to sense lightning strikes at distances of up to 30 km, thus functioning as a lightning detector. In late 1895, Popov built a version of the receiver that was capable of automatically recording lightning strikes on paper rolls. Popov's system was eventually extended to function as a wireless telegraph, with a Morse key attached to the transmitter. There's some dispute regarding the first public test of this design. It is frequently stated that Popov used his radio to send a Morse code message over a distance of 250 m in 26 March 1896 (three months before Marconi's patent was filed). However, contemporary confirmations of this transmission are lacking. It is more likely that said experiment took place in December 1897.

In 1900, a radio station was established under Popov's instructions on Hogland island (Suursaari) to provide two-way communication by wireless telegraphy between the Russian naval base and the crew of the battleship General-Admiral Apraksin. By February 5 messages were being received reliably. The wireless messages were relayed to Hogland Island by a station some 25 miles (40 km) away at Kymi (nowadays Kotka) on the Finnish coast. Later Popov experimented with ship-to-shore communication. Popov died in 1905 and his claim was not pressed by the Russian government until 1945.

Cervera

In May–June 1899, Julio Cervera Baviera worked to develop his own system. After visiting Marconi’s radiotelegraphic installations on the English Channel, he began collaborating with Marconi on resolving the problem of a wireless communication system, obtaining some patents by the end of 1899. Cervera, who worked with Marconi and his assistant, George S. Kemp, in 1899, resolved the issues with their wireless telegraph. He obtained his first patents prior to the end of that year.

Marconi

Guglielmo Marconi studied at the Leghorn Technical School, and acquainted himself with the published writings of Professor Augusto Righi of the University of Bologna. In 1894, Sir William Preece delivered a paper to the Royal Institution in London on electric signalling without wires. In 1894 at the Royal Institution lectures, Lodge delivers "The Work of Hertz and Some of His Successors". Marconi is said to have read, while on vacation in 1894, about the experiments that Hertz did in the 1880s. Marconi also read about Tesla's work. It was at this time that Marconi began to understand that radio waves could be used for wireless communications. Marconi's early apparatus was a development of Hertz’s laboratory apparatus into a system designed for communications purposes. At first Marconi used a transmitter to ring a bell in a receiver in his attic laboratory. He then moved his experiments out-of-doors on the family estate near Bologna, Italy, to communicate further. He replaced Hertz’s vertical dipole with a vertical wire topped by a metal sheet, with an opposing terminal connected to the ground. On the receiver side, Marconi replaced the spark gap with a metal powder coherer, a detector developed by Edouard Branly and other experimenters. Marconi transmitted radio signals for about 1.5 miles (2.4 km) at the end of 1895.

Marconi was awarded a patent for radio with British patent No. 12,039, Improvements in Transmitting Electrical Impulses and Signals and in Apparatus There-for. The complete specification was filed March 2, 1897. This was Marconi's initial patent for the radio, though it used various earlier techniques of various other experimenters and resembled the instrument demonstrated by others (including Popov). During this time spark-gap wireless telegraphy was widely researched. In July, 1896, Marconi got his invention and new method of telegraphy to the attention of Preece, then engineer-in-chief to the British Government Telegraph Service, who had for the previous twelve years interested himself in the development of wireless telegraphy by the inductive-conductive method. On June 4, 1897, he delivered "Signalling through Space without Wires". Preece devoted considerable time to exhibiting and explaining the Marconi apparatus at the Royal Institution in London, stating that Marconi invented a new relay which had high sensitiveness and delicacy.

Marconi plain aerial, 1896 receiver

Muirhead Morse inker

IThe Marconi Company Ltd. was founded by Marconi in 1897, known as the Wireless Telegraph Trading Signal Company. Also in 1897, Marconi established the radio station at Niton, Isle of Wight, England. Marconi's wireless telegraphy was inspected by the Post Office Telegraph authorities; they made a series of experiments with Marconi's system of telegraphy without connecting wires, in the Bristol Channel. The October wireless signals of 1897 were sent from Salisbury Plain to Bath, a distance of 34 miles (55 km). Around 1900 Marconi developed an empirical law that, for simple vertical sending and receiving antennas of equal height, the maximum working telegraphic distance varied as the square of the height of the antenna. This became known as Marconi's law.

Other experimental stations were established at Lavernock Point, near Penarth; on the Flat Holmes, an island in mid-channel, and at Brean Down, a promontory on the Somerset side. Signals were obtained between the first and last-named points, a distance of, approximately, 8 miles (13 km). The receiving instrument used was a Morse inkwriter of the Post Office pattern. In 1898, Marconi opened a radio factory in Hall Street, Chelmsford, England, employing around 50 people. In 1899, Marconi announced his invention of the "iron-mercury-iron coherer with telephone detector" in a paper presented at Royal Society, London.

In May, 1898, communication was established for the Corporation of Lloyds between Ballycastle and the Lighthouse on Rathlin Island in the North of Ireland. In July, 1898, the Marconi telegraphy was employed to report the results of yacht races at the Kingston Regatta for the Dublin Express newspaper. A set of instruments were fitted up in a room at Kingstown, and another on board a steamer, the Flying Huntress. The aerial conductor on shore was a strip of wire netting attached to a mast 40 feet (12 m) high, and several hundred messages were sent and correctly received during the progress of the races.

At this time His Majesty King Edward VII, then Prince of Wales, had the misfortune to injure his knee, and was confined on board the royal yacht Osltorm in Cowes Bay. Marconi fitted up his apparatus on board the royal yacht by request, and also at Osborne House, Isle of Wight, and kept up wireless communication for three weeks between these stations. The distances covered were small; but as the yacht moved about, on some occasions high hills were interposed, so that the aerial wires were overtopped by hundreds of feet, yet this was no obstacle to communication. These demonstrations led the Corporation of Trinity House to afford an opportunity for testing the system in practice between the South Foreland Lighthouse, near Dover, and the East Goodwin Lightship, on the Goodwin Sands. This installation was set in operation on December 24, 1898, and proved to be of value. It was shown that when once the apparatus was set up it could be worked by ordinary seamen with very little training.

At the end of 1898 electric wave telegraphy established by Marconi had demonstrated its utility, especially for communication between ship and ship and ship and shore.

The Haven Hotel station and Wireless Telegraph Mast was where much of Marconi's research work on wireless telegraphy was carried out after 1898. In 1899, he transmitted messages across the English Channel. Also in 1899, Marconi delivered "Wireless Telegraphy" to the Institution of Electrical Engineers. In addition, in 1899, W. H. Preece delivers "Aetheric Telegraphy", stating that the experimental stage in wireless telegraphy had been passed in 1894 and inventors were then entering the commercial stage. Preece, continuing in the lecture, details the work of Marconi and other British inventors. In October, 1899, the progress of the yachts in the international race between the Columbia and Shamrock was successfully reported by aerial telegraphy, as many as 4,000 words having been (as is said) despatched from the two ship stations to the shore stations. Immediately afterward the apparatus was placed by request at the service of the United States Navy Board, and some highly interesting experiments followed under Marconi's personal supervision. The Marconi Company was renamed Marconi's Wireless Telegraph Company in 1900.

Marconi watching associates raise kite antenna at St. John's, December 1901

In 1901, Marconi claimed to have received daytime transatlantic radio frequency signals at a wavelength of 366 metres (820 kHz). Marconi established a wireless transmitting station at Marconi House, Rosslare Strand, Co. Wexford in 1901 to act as a link between Poldhu in Cornwall and Clifden in Co. Galway. His announcement on 12 December 1901, using a 152.4-metre (500 ft) kite-supported antenna for reception, stated that the message was received at Signal Hill in St John's, Newfoundland (now part of Canada) via signals transmitted by the company's new high-power station at Poldhu, Cornwall. The message received had been prearranged and was known to Marconi, consisting of the Morse letter 'S' - three dots. Bradford has recently contested the reported success, however, based on theoretical work as well as a reenactment of the experiment. It is now well known that long-distance transmission at a wavelength of 366 meters is not possible during the daytime, because the skywave is heavily absorbed by the ionosphere. It is possible that what was heard was only random atmospheric noise, which was mistaken for a signal, or that Marconi may have heard a shortwave harmonic of the signal. The distance between the two points was about 3,500 kilometres (2,200 mi).

The Poldhu to Newfoundland transmission claim has been criticized. There are various science historians, such as Belrose and Bradford, who have cast doubt that the Atlantic was bridged in 1901, but other science historians have taken the position that this was the first transatlantic radio transmission. Critics have claimed that it is more likely that Marconi received stray atmospheric noise from atmospheric electricity in this experiment. The transmitting station in Poldhu, Cornwall used a spark-gap transmitter that could produce a signal in the medium frequency range and with high power levels.

Marconi transmitted from England to Canada and the United States. In this period, a particular electromagnetic receiver, called the Marconi magnetic detector or hysteresis magnetic detector, was developed further by Marconi and was successfully used in his early transatlantic work (1902) and in many of the smaller stations for a number of years. In 1902, a Marconi station was established in the village of Crookhaven, County Cork, Ireland to provide marine radio communications to ships arriving from the Americas. A ship's master could contact shipping line agents ashore to enquire which port was to receive their cargo without the need to come ashore at what was the first port of landfall. Ireland was also, due to its western location, to play a key role in early efforts to send trans-Atlantic messages. Marconi transmitted from his station in Glace Bay, Nova Scotia, Canada across the Atlantic, and on 18 January 1903 a Marconi station sent a message of greetings from Theodore Roosevelt, the President of the United States, to the King of the United Kingdom, marking the first transatlantic radio transmission originating in the United States

Cunard Daily Bulletin

In 1904, Marconi opened the ocean daily newspaper, the Cunard Daily Bulletin, on the R.M.S. "Campania." At the start, the passing events were printed in a little pamphlet of four pages called the Cunard Bulletin. The title would read Cunard Daily Bulletin, with subheads for "Marconigrams Direct to the Ship." All the passenger ships of the Cunard Company are fitted with Marconi's system of wireless telegraphy, by means of which constant communication was kept up, either with other ships or with land stations on the eastern or western hemisphere. The RMS Lucania, Oct., 1903, with Marconi on board, was the first vessel to hold communication with both sides of the Atlantic. The Cunard Daily Bulletin, a thirty-two page illustrated paper published on board these boats, recorded news received by wireless telegraphy, and is first ocean newspaper. In August, 1903, in agreement was made with the British Government by which the Cunard Co. were to build two steamers, to be, with all other Cunard ships, at the disposal of the British Admiralty for hire or purchase whenever they may be required, the Government lending the company £2,600,000 to build the ships and granting them a subsidy £150,000 a year. One was the RMS Lusitania and the RMS Mauritania.

In June and July 1923, Marconi's shortwave transmissions were completed during nights on 97 meters from Poldhu Wireless Station, Cornwall, to his yacht Elettra in the Cape Verde Islands. In September 1924, Marconi transmitted during daytime and nighttime on 32 meters from Poldhu to his yacht in Beirut. Marconi, in July 1924, entered into contracts with the British General Post Office (GPO) to install telegraphy circuits from London to Australia, India, South Africa and Canada as the main element of the Imperial Wireless Chain. The UK-to-Canada shortwave "Beam Wireless Service" went into commercial operation on 25 October 1926. Beam Wireless Services from the UK to Australia, South Africa and India went into service in 1927. Electronic components for the system were built at Marconi's New Street wireless factory in Chelmsford.

Marconi would jointly receive the 1909 Nobel Prize in Physics with Karl Ferdinand Braun for contributions to the existing radio sciences. Marconi's demonstrations of the use of radio for wireless communications, equipping ships with life saving wireless communications, establishing the first transatlantic radio service, and building the first stations for the British short wave service, have marked his place in history. Shortly after the turn of the 20th century, the US Patent Office re-awarded Marconi a patent for radio. The U.S. patent RE11913 was granted on June 4, 1901. Marconi's U.S. patent 676,332 was awarded on June 11, 1901, also. This system was more advanced than his previous works. The United States Supreme Court, decision of MARCONI WIRELESS T. CO. OF AMERICA v. U.S., 320 U.S. 1 (1943) stated that “Marconi's reputation as the man who first achieved successful [transatlantic] radio transmission … is not here in question” this statement is followed by “Marconi's patent involved no invention over Lodge, Tesla, and Stone”. The 1943 decision didn't overturn Marconi's original patents, or his reputation as the first person to develop practical radiotelegraphic communication. It just said that the adoption of adjustable transformers in the transmitting and receiving circuits, which was an improvement of the initial invention, was anticipated by patents issued to Oliver Lodge and John Stone. (This decision wasn't unanimous).

Braun

Braun's radiant energy U.S. patent 750,429.

Ferdinand Braun's major contributions were the introduction of a closed tuned circuit in the generating part of the transmitter, and its separation from the radiating part (the antenna) by means of inductive coupling, and later on the usage of crystals for receiving purposes. Braun experimented at first at the University of Strasbourg. Braun had written extensively on wireless subjects and was well known through his many contributions to the Electrician and other scientific journals. In 1899, he would apply for the patents, Electro telegraphy by means of condensers and induction colls and Wireless electro transmission of signals over surfaces.

Pioneers working on wireless devices eventually came to a limit of distance they could cover. Connecting the antenna directly to the spark gap produced only a heavily damped pulse train. There were only a few cycles before oscillations ceased. Braun's circuit afforded a much longer sustained oscillation because the energy encountered less loss swinging between coil and Leyden Jars. Also, by means of inductive antenna coupling the radiator was matched to the generator.

In spring 1899 Braun, accompanied by his colleagues Cantor and Zenneck, went to Cuxhaven to continue their experiments at the North Sea. On February 6, 1899, he would apply for the United States Patent, Wireless Electric Transmission of Signals Over Surfaces. Not before long he bridged a distance of 42 km to the city of Mutzing. On 24 September 1900 radio telegraphy signals were exchanged regularly with the island of Heligoland over a distance of 62 km. Lightvessels in the river Elbe and a coast station at Cuxhaven commenced a regular radio telegraph service. On August 6, 1901, he would apply for Means for Tuning and Adjusting Electric Circuits.

By 1904, the closed circuit system of wireless telegraphy, connected with the name of Braun, was well known and generally adopted in principle. The results of Braun's experiments, published in the Electrician, possess interest, apart from the method employed. Braun showed how the problem could be satisfactorily and economically solved. The closed circuit oscillator has the advantage, as was known, of being able to draw upon the kinetic energy in the oscillator circuit, and thus, because such a circuit can be given a much greater capacity than can be obtained with a radiating aerial alone, much more energy can be stored up and radiated by its employment. The emission is also prolonged, both results tending towards the attainment of the much desired train of undamped waves. The energy available, though greater than with the open system, was still inconsiderable unless very high potentials, with the attendant drawbacks, were used. Braun avoided the use of extremely high potentials for charging the gap and also makes use of a less wasteful gap by sub-dividing it. The chief point in his new arrangement, however, is not the sub-division of the gap merely but their arrangement, by which they are charged in parallel, at low voltages, and discharge in series. The Nobel Prize awarded to Braun in 1909 depicts this design.

Naval wireless

The United States Navy Board had issued an 1899 report on the results of investigations of the Marconi system of wireless telegraphy. The report, Notes On The Marconi Wireless Telegraphy was published in full in the Electrician, and from it the following statements concerning the efficiency of the system have been taken: It was well adapted for use in squadron signalling under conditions of rain, fog, darkness and motion of speed. Wind, rain, fog, and other conditions of weather do not affect the transmission through space, but dampness may reduce the range, rapidity, and accuracy by impairing the insulation of the aerial wire and the instruments. Darkness has no effect. When two transmitters are sending at the same time, all the receiving wires within range receive the impulses from transmitters, and the tapes, although unreadable, show unmistakably that such double sending was taking place. In every case, under a great number of varied conditions, the attempted interference was complete. Marconi, although he stated to the Board before these attempts were made that he could prevent interference, never explained how nor made any attempt to demonstrate that it could be done. Between large ships (heights of masts 130 feet (40 m) and 140 feet (43 m)) and a torpedo-boat (height of mast 45 feet (14 m)), across open water, signals can be read up to 7 miles (11 km) on the torpedo-boat and 85 miles (137 km) on the ship. Communication might be interrupted altogether when tall buildings of iron framing intervene. The rapidity was not greater than twelve words per minute for skilled operators. The sending apparatus and wire would injuriously affect the compass if placed near it. The exact distance were not known, and would be determined by experiment. The system was adapted for use on all vessels of the navy, including torpedo-boats and small vessels, as patrol boats, scout boats, and despatch boats, but it was impracticable in a small boat. For landing parties the only feasible method of use would be to erect a pole on shore and then communicate with the ship. The system could be adapted to the telegraphic determination of differences of longitude in surveying. According to the Proceedings of the United States Naval Institute, the Marconi instruments that were tested found that the

"[...] coherer, principle of which was discovered some twenty years ago, [was] the only electrical instrument or device contained in the apparatus that is at all new".

— United States Naval Institute, 1899

The Board respectfully recommended that the system be given a trial in the United States Navy.

The HMS Hector became the first British warship to have wireless telegraphy installed when she conducted the first trials of the new equipment for the Royal Navy. Starting in December 1899, the HMS Hector and HMS Jaseur were outfitted with wireless equipment. In 1901, HMS Jaseur received signals from the Marconi transmitter on the Isle of Wight and from the HMS Hector (25 January).

Stone Stone

John Stone Stone labored as an early telephone engineer and was influential in developing wireless communication technology, and holds dozens of key patents in the field of "space telegraphy". Patents of Stone for radio, together with their equivalents in other countries, form a very voluminous contribution to the patent literature of the subject. More than seventy United States patents have been granted to this patentee alone. In many cases these specifications are learned contributions to the literature of the subject, filled with valuable references to other sources of information.

Stone has had issued to him a large number of patents embracing a method for impressing oscillations on a radiator system and emitting the energy in the form of waves of predetermined length whatever may be the electrical dimensions of the oscillator. On February 8, 1900, he filed for a selective system in U.S. patent 714,756. In this system, two simple circuits are associated inductively, each having an independent degree of freedom, and in which the restoration of electric oscillations to zero potential the currents are superimposed, giving rise to compound harmonic currents which permit the resonator system to be syntonized with precision to the oscillator. Stone's system, as stated in U.S. patent 714,831, developed free or unguided simple harmonic electromagnetic signal waves of a definite frequency to the exclusion of the energy of signal waves of other frequencies, and an elevated conductor and means for developing therein forced simple electric vibrations of corresponding frequency. In these patents Stone devised a multiple inductive oscillation circuit with the object of forcing on the antenna circuit a single oscillation of definite frequency. In the system for receiving the energy of free or unguided simple harmonic electromagnetic signal waves of a definite frequency to the exclusion of the energy of signal waves of other frequencies, he claimed an elevated conductor and a resonant circuit associated with said conductor and attuned to the frequency of the waves, the energy of which is to be received. A coherer made on what is called the Stone system was employed in some of the portable wireless outfits of the United States Army. The Stone Coherer has two small steel plugs between which are placed loosely packed carbon granules. This is a self-decohering device; though not as sensitive as other forms of detectors it is well suited to the rough usage of portable outfits.

Wireless telephony

Fessenden

In late 1886, Reginald A. Fessenden began working directly for Thomas Edison at the inventor's new laboratory in West Orange, New Jersey. Fessenden quickly made major advances, especially in receiver design, as he worked to develop audio reception of signals. The United States Weather Bureau began, early in 1900, a systematic course of experimentation in wireless telegraphy, employing him as a specialist. Fessenden evolved the heterodyne principle here where two signals combined to produce a third signal.

In 1900, construction began on a large radio transmitting alternator. Fessenden, experimenting with a high-frequency spark transmitter, successfully transmitted speech on December 23, 1900 over a distance of about 1.6 kilometres (0.99 mi), the first audio radio transmission. Early in 1901 the Weather Bureau officially installed Fessenden at Wier's Point, Roanoke Island, North Carolina, and he made experimental transmissions across water to a station located about 5 miles (8.0 km) west of Cape Hatteras, the distance between the two stations being almost exactly 50 miles (80 km). An alternator of 1 kW output at 10 kilohertz was built in 1902. The credit for the development of this machine is due to Charles Proteus Steinmetz, Caryl D. Haskins, Ernst Alexanderson, John T. H. Dempster, Henry Geisenhoner, Adam Stein, Jr., and F. P. Mansbendel.

In a paper written by Fessenden in 1902, it was asserted that important advances had been made, one of which was overcoming largely the loss of energy experienced in other systems. In an interview with a New York Journal correspondent, Fessenden stated that in his early apparatus he did not use an air transformer at the sending end, nor a concentric cylinder for emitters and antennae, and had used capacity, but arranged in a manner entirely different from that in other systems, and that he did not employ a coherer or any form of imperfect contact. Fessenden asserted that he had paid particular attention to selective and multiplex systems, and was well satisfied with the results in that direction. On August 12, 1902, 13 patents were issued to Fessenden, covering various methods, devices, and systems for signaling without wires. These patents involved many new principles, the chef-d'oeuvre of which was a method for distributing capacity and inductance instead of localizing these coefficients of the oscillator as in previous systems.

Brant rock radio tower (1910)

By the summer of 1906, a machine producing 50 kilohertz was installed at the Brant Rock station, and in the fall of 1906, what was called an electric alternating dynamo was working regularly at 75 kilohertz, with an output of 0.5 kW. Fessenden used this for wireless telephoning to Plymouth, a distance of approximately 11 miles (18 km). In the following year machines were constructed having a frequency of 96 kilohertz and outputs of 1 kW and 2 kW. Fessenden believed that the damped wave-coherer system was essentially and fundamentally incapable of development into a practical system. He would employ a two-phase high frequency alternator method and the continuous production of waves with changing constants of sending circuit. Fessenden would also use duplex and multiplex commutator methods. On Dec. 11, 1906, operation of the wireless transmission in conjunction with the wire lines took place. In July 1907 the range was considerably extended and speech was successfully transmitted between Brant Rock and Jamaica, on Long Island, a distance of nearly 200 miles (320 km), in daylight and mostly over land, the mast at Jamaica being approximately 180 feet (55 m) high.

Fleming

In November 1904, John Ambrose Fleming invented the two-electrode vacuum-tube rectifier, which he called the Fleming oscillation valve. He would later patent this invention. This "Fleming Valve" was sensitive and reliable, and so it replaced the crystal diode used in receivers used for long-distance wireless communication. It had an advantage, that it could not be permanently injured or set out of adjustment by any exceptionally strong stray signal, such as those due to atmospheric electricity. Fleming earned a Hughes Medal in 1910 for his electronic achievements.

Fleming recognized the use of the rectifying properties of a wireless tube for the indication of high frequency oscillations, and used it as a electromagnetic detector. On November 7, 1905, he would be granted U.S. patent 803,684. Marconi used this device as a radio detector, also. His detector was par excellence for large antenna or high-power stations.

The Supreme Court of the United States would eventually invalidate the patent because of an improper disclaimer and, additionally, maintained the technology in the patent was known art when filed. This invention was the first vacuum tube. Fleming's diode was used in radio receivers for many decades afterward, until it was superseded by improved solid state electronic technology more than 50 years later.

De Forest

Lee De Forest had an interest in wireless telegraphy and he invented the Audion in 1906. He was president and secretary of the De Forest Radio Telephone and Telegraph Company (1913). The De Forest System was adopted by the United States Government, and had been demonstrated to other Governments including those of Great Britain, Denmark, Germany, Russia, and British Indies, all of which purchased De Forest apparatus previous to the Great War. De Forest is one of the fathers of the "electronic age", as the Audion helped to usher in the widespread use of electronics.

De Forest made the Audion tube from a vacuum tube. He also made the "Oscillion", an undamped wave transmitter. He developed the De Forest method of wireless telegraphy and founded the American De Forest Wireless Telegraph Company. De Forest was a distinguished electrical engineer and the foremost American contributor to the development of wireless telegraphy and telephony. The elements of his device takes relatively weak electrical signals and amplifies them. The Audion Detector, Audion Amplifier, and the "Oscillion" transmitter had furthered the radio art and the transmission of written or audible speech. In World War I, the De Forest system was a factor in the efficiency of the United States Signal Service, and was also installed by the United States Government in Alaska.

Radio invention timeline

Main article: Timeline of radio

Below is a brief selection of important events and individuals related to the development of radio, from 1860 to 1910.

See also

People

Edwin Howard Armstrong, Greenleaf Whittier Pickard, Ernst Alexanderson, Archie Frederick Collins

Radio

Radio communication system, Timeline of radio, Oldest radio station, Birth of public radio broadcasting, Crystal radio

Categories

Radio People, Radio Pioneers, Discovery and invention controversies

Other

List of persons considered father or mother of a field, Radiotelegraph and Spark-Gap Transmitters, The Great Radio Controversy, Induction coil, Ruhmkorff coil, Poldhu, Alexanderson alternator, De Forest tube

Further reading

• Anderson, L.I., "Priority in the Invention of Radio: Tesla vs. Marconi", Antique Wireless Association Monograph No. 4, March, 1980.
• Anderson, L.I., "John Stone Stone on Nikola Tesla's Priority in Radio and Continuous-Wave Radiofrequency Apparatus", The AWA Review, Vol. 1, 1986, pp. 18–41.
• Brand, W.E., "Rereading the Supreme Court: Tesla's Invention of Radio", Antenna, Volume 11 No. 2, May 1998, Society for the History of Technology
• Lauer, H., & Brown, H. L. (1919). Radio engineering principles. New York: McGraw-Hill book company; [etc., etc.]
• Rockman, H. B. (2004). Intellectual property law for engineers and scientists. New York [u.a.: IEEE Press].

External links

United States Court case

• "Marconi Wireless Tel. Co. v. United States, 320 U.S. 1 (U.S. 1943)", 320 U.S. 1, 63 S. Ct. 1393, 87 L. Ed. 1731 Argued April 9,12, 1943. Decided June 21, 1943.

Books and articles

listed by date, earliest first

• Telegraphing across space, Electric wave method. The Electrical engineer. (1884). London: Biggs & Co. (ed., the article is broke up, it begins on p. 466 and continues on p. 493.)
• Fahie, J. J. (1900). A history of wireless telegraphy, 1838-1899: including some bare-wire proposals for subaqueous telegraphs. Edinburgh: W. Blackwood and Sons.
• Thompson, S. P., Homans, J. E., & Tesla, N. (1903). Polyphase electric currents and alternate-current motors. "Wireless Telegraphy". The library of electrical science, v. 6. New York: P.F. Collier & Son.
• Sewall, C. H. (1904). Wireless telegraphy: its origins, development, inventions, and apparatus. New York: D. Van Nostrand.
• Trevert, E. (1904). The A.B.C. of wireless telegraphy; a plain treatise on Hertzian wave signaling; embracing theory, methods of operation, and how to build various pieces of the apparatus employed. Lynn, Mass: Bubier Pub.
• Collins, A. F. (1905). Wireless telegraphy; its history, theory and practice. New York: McGraw Pub.
• Mazzotto, D., & Bottone, S. R. (1906). Wireless telegraphy and telephony. London: Whittaker & Co.
• Erskine-Murray, J. (1907). A handbook of wireless telegraphy: Its theory and practice, for the use of electrical engineers, students, and operators. London: Crosby Lockwood and Son. (ed., also available in the Van Nostrand (1909) version).
• Murray, J. E. (1907). A handbook of wireless telegraphy. New York: D. Van Nostrand Co.; [etc.]
• Simmons, H. H. (1908). "Wireless telegraphy", Outlines of electrical engineering. London: Cassell and Co.
• Fleming, J. A. (1908). The principles of electric wave telegraphy. London: New York and Co.
• Twining, H. L. V., & Dubilier, W. (1909). Wireless telegraphy and high frequency electricity; a manual containing detailed information for the construction of transformers, wireless telegraph and high frequency apparatus, with chapters on their theory and operation. Los Angeles, Cal: The author.
• Bottone, S. R. (1910). Wireless telegraphy and Hertzian waves. London: Whittaker & Co.
• Bishop, L. W. (1911). The wireless operators' pocketbook of information and diagrams. Lynn, Mass: Bubier Pub. Co.; [etc., etc.].
• Massie, W. W., & Underhill, C. R. (1911). Wireless telegraphy and telephony popularly explained. New York: D. Van Nostrand.
• Ashley, C. G., & Hayward, C. B. (1912). Wireless telegraphy and wireless telephony: an understandable presentation of the science of wireless transmission of intelligence. Chicago: American School of Correspondence.
• Stanley, R. (1914). Text book on wireless telegraphy. London: Longmans, Green.
• Thompson, S. P. (1915). Elementary lessons in electricity and magnetism. New York: Macmillan
• Bucher, E. E. (1917). Practical wireless telegraphy: A complete text book for students of radio communication. New York: Wireless Press, Inc.
• American Institute of Electrical Engineers. (1919). Transactions of the American Institute of Electrical Engineers. New York: American Institute of Electrical Engineers. (ed., Contains Radio Telephony — By E. B. Craft and E. H. Colpitts (Illustrated). Page 305)
• Stanley, R. (1919). Text-book on wireless telegraphy. London: Longmans, Green.

Encyclopedias

• Chisholm, H. (1910). The encyclopædia britannica: A dictionary of arts, sciences, literature and general information. Cambridge, Eng: At the University press. "Telegraph", "Part II - Wireless Telegraphy".
• American Technical Society. (1914). Cyclopedia of applied electricity: A general reference work on direct-current generators and motors, storage batteries, electrochemistry, welding, electric wiring, meters, electric light transmission, alternating-current machinery, telegraphy, etc. Volume 7. Wireless Telegraphy and Telephony By C. G. Ashley Page 147. Chicago: American technical society.
• Colby, F. M., Williams, T., & Wade, H. T. (1922). "Wireless Telegraphy", The New international encyclopaedia. New York: Dodd, Mead and Co.
• "Wireless telegraphy", The Encyclopaedia Britannica. (1922). London: Encyclopædia Britannica.

Gutenberg project

• The New Physics and Its Evolution. Chapter VII : A Chapter in the History of Science: Wireless telegraphy by Lucien Poincaré, eBook #15207, released February 28, 2005.

Websites

• Comparative Study of the Hertz, Marconi and Tesla Low-Frequency Wireless Systems
• Howeth, Captain H.S. History of Communications – Electronics in the United States Navy, published 1963, GPO, 657 pages. Free online public domain US government published book.
• Wunsch, A.D., "Misreading the Supreme Court,” Antenna, Volume 11 No. 1, November 1998, Society for the History of Technology
• Katz, Randy H., "Look Ma, No Wires": Marconi and the Invention of Radio". History of Communications Infrastructures* Timeline: First Thirty Years of Radio, 1895-1925.
• White, Thomas H. (November 1, 2012). "Nikola Tesla: The Guy Who DIDN'T "Invent Radio"".