Invention of radio

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

Within the history of radio, several people were involved in the invention of radio and there were many key inventions in what became the modern systems of wireless. Radio development began as "wireless telegraphy". Closely related, radio was developed along with two other key inventions, the telegraph and the telephone. During the early development of wireless technology and long after its wide use, disputes persisted as to who could claim credit for the invention of radio. The matter was important for economic, political and nationalistic reasons.

Physics of wireless signalling

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 waves

All these physical phenomena, as well as more speculative concepts such as conduction through air, have been tested for purposes 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 generally today for long-distance wireless communications involves the use of modulation of electromagnetic waves, which is radio.

Radio antennas radiate electromagnetic waves that can reach the receiver either by ground wave propagation, by refraction from the ionosphere, known as sky wave propagation, and occasionally by refraction in lower layers of the atmosphere (tropospheric ducting). The ground wave component is the portion of the radiated electromagnetic wave that propagates close to the Earth's surface. It has both direct-wave and ground-reflected components. The direct-wave is limited only by the distance from the transmitter to the horizon plus a distance added by diffraction around the curvature of the earth. The ground-reflected portion of the radiated wave reaches the receiving antenna after being reflected from the Earth's surface. A portion of the ground wave energy radiated by the antenna may also be guided by the Earth's surface as a ground-hugging surface wave.

Theory of electromagnetism

Main article: History of electromagnetism

Experiments and Theory

Jospeh Henry James Clerk Maxwell

Early theories and experiments

Several scientists speculated that light might be some kind of wave connected with electricity or magnetism. Around 1830 Francesco Zantedeschi suggested a connection between light, electricity, and magnetism. In 1832 Joseph Henry performed experiments detecting electromagnetic effects over a distance of 200 feet and postulated the existence of electromagnetic waves. In 1846 Michael Faraday speculated that light was a wave disturbance in a force field".

Wireless experiments of the 19th century

In the late 19th century it was clear to various scientists and experimenters that wireless communication was possible. Various theoretical and experimental innovations led to the development of radio and the communication system we know today. Some early work was done by local effects and experiments of electromagnetic induction. Many understood that there was nothing similar to the "ethereal telegraphy" and telegraphy by induction; the phenomena being wholly distinct. Wireless telegraphy was beginning to take hold and the practice of transmitting messages without wires was being developed. Many people worked on developing the devices and improvements.

Faraday

James Clerk Maxwell, a theoretical physicist who developed a set of equations describing electromagnetic waves. These later became known as Maxwell's equations.

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.

Maxwell

Between 1861 and 1865, based on the earlier experimental work of Faraday and other scientists, 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."

William Henry Ward

In April 1872 William Henry Ward received U.S. patent 126,356 for radio development. However, this patent did not refer to any known scientific theory of electromagnetism and could never have received and transmitted radio waves.

Mahlon Loomis

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 substantially similar to William Henry Ward's patent and could not have transmitted and received radio waves.

Edison (1875)

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.

David E. Hughes

In 1878, David E. Hughes noticed that sparks could be heard in a telephone receiver when experimenting with his carbon microphone. He developed this carbon-based detector further and eventually could detect signals over a few hundred yards. He demonstrated his discovery to the Royal Society in 1880, but was told it was merely induction, and therefore abandoned further research.

Edouard Branly

In 1890, Edouard Branly of France developed the coherer.

Edison (1885)

In 1885, Edison took out U.S. patent 465,971 on a system of radio communication between ships (which later he sold to Marconi). The patent, however, was not based on the transmission and reception of electromagnetic waves.

Hertz

Between 1886 and 1888, Heinrich Rudolf Hertz studied Maxwell's theory and validated it through experiment. He demonstrated the transmission and reception of the electromagnetic waves predicted by Maxwell and thus was the first person to intentionally transmit and receive radio. He discovered that the electromagnetic equations could be reformulated into a partial differential equation called the wave equation. Famously, he saw no practical use for his discovery. For more information see Hertz' radio work at Invention of radio.

Stubblefield

Claims have been made that Murray, Kentucky farmer Nathan Stubblefield developed radio between 1885 and 1892, before either Tesla or Marconi, but his devices seemed to have worked by induction transmission rather than radio transmission.

Landell de Moura

Between 1893 and 1894, Roberto Landell de Moura, a Brazilian priest and scientist, conducted experiments in wireless transmissions. He did not publicize his achievement until 1900, when he held a public demonstration of a wireless transmission of voice in São Paulo, Brazil on June 3.

Beginnings of radio

File:NikolaTeslaLightbulb.jpg

Nikola Tesla developed means to reliably produce radio frequencies, publicly demonstrated the principles of radio, and transmitted long distant signals.

There are varying disputed claims about who invented radio, which in the beginning was called "wireless telegraphy". The key invention for the beginning of "wireless transmission of data using the entire frequency spectrum", known as the spark-gap transmitter, has been attributed to various men. Marconi equipped ships with lifesaving wireless communications and established the first transatlantic radio service. Tesla developed means to reliably produce radio frequency electrical currents, publicly demonstrated the principles of radio, and transmitted long distance signals.

Nikola Tesla

In 1891 Tesla began his research into radio. He later published an article, "The True Wireless", concerning this research. In 1892 he gave a lecture called "Experiments with Alternate Currents of High Potential and High Frequency", in London (Available at Project Gutenberg). In 1893, at St. Louis, Missouri, Tesla gave a public demonstration of "wireless" radio communication. Addressing the Franklin Institute in Philadelphia and the National Electric Light Association, he described in detail the principles of radio communication.

The apparatus that Tesla used contained all the elements that were incorporated into radio systems before the development of the "oscillation valve", the early vacuum tube. Tesla initially used sensitive electromagnetic receivers, that were unlike the less responsive coherers later used by Marconi and other early experimenters.

Afterward, the principle of radio communication (sending signals through space to receivers) was publicized widely from Tesla's experiments and demonstrations. Various scientists, inventors, and experimenters began to investigate wireless methods. For more information see Tesla's wireless work.

Oliver Lodge

Oliver Lodge transmitted radio signals on August 14, 1894 (one year after Tesla, five years after Heinrich Hertz and one year before Marconi) at a meeting of the British Association for the Advancement of Science at Oxford University. (In 1995, the Royal Society recognized this scientific breakthrough at a special ceremony at Oxford University. For more information, see Past Years: An Autobiography, New York: Charles Scribner's Sons, p231.)

On 19 August 1894 Lodge demonstrated the reception of Morse code signalling via radio waves using a "coherer". He improved Edouard Branly's coherer radio wave detector 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 was key to the "syntonic" tuning concept. In 1912 Lodge sold the patent to Marconi.

Jagdish Chandra Bose

In November 1894, the Indian physicist, Jagdish 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, proving that communication signals can be sent without using wires. He was thus the first to send and receive radio waves over a significant distance but did not commercially exploit this achievement.

The 1895 public demonstration by Bose in Calcutta was before Marconi's wireless signalling experiment on Salisbury Plain in England in May 1897. 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."

Alexander Popov

Popov was the first man to demonstrate the practical applications of radio waves.

In 1895, the Russian physicist Alexander Popov built a coherer. On May 7, 1895, 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: this day has since been celebrated in Russia as "Radio Day". 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.

Around March 1896 Popov demonstrated in public the transmission of radio waves, between different campus buildings, to the Saint Petersburg Physical Society. (This was before the public demonstration of the Marconi system around September 1896.) 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 30 miles away. In 1900, Popov stated at the Congress of Russian Electrical Engineers that,

"the emission and reception of signals by Marconi by means of electric oscillations was nothing new, as in America Nikola Tesla did the same experiments in 1893."

Later Popov experimented with ship-to-shore communication. Popov died in 1905 and his claim was not pressed by the Russian government until 1945.

Ernest Rutherford

The New Zealander Ernest Rutherford, 1st Baron Rutherford of Nelson was instrumental in the development of radio. In 1895 he was awarded an Exhibition of 1851 Science Research Scholarship to Cambridge. He arrived in England with a reputation as an innovator and inventor, and distinguished himself in several fields, initially by working out the electrical properties of solids and then using wireless waves as a method of signalling. Rutherford was encouraged in his work by Sir Robert Ball, who had been scientific adviser to the body maintaining lighthouses on the Irish coast; he wished to solve the difficult problem of a ship's inability to detect a lighthouse in fog. Sensing fame and fortune, Rutherford increased the sensitivity of his apparatus until he could detect electromagnetic waves over a distance of several hundred meters. The commercial development, though, of wireless technology was left for others, as Rutherford continued purely scientific research. Thomson quickly realised that Rutherford was a researcher of exceptional ability and invited him to join in a study of the electrical conduction of gases.

Guglielmo Marconi

Guglielmo Marconi was an electrical engineer and Nobel laureate known for the development of a practical wireless telegraphy system.

In 1896, Guglielmo Marconi was awarded a patent for radio with British Patent 12039, Improvements in Transmitting Electrical Impulses and Signals and in Apparatus There-for. This was the initial patent for the radio, though it used various earlier techniques of various other experimenters (primarily Tesla) and resembled the instrument demonstrated by others (including Popov). During this time spark-gap wireless telegraphy was widely researched.

In 1896, Bose went to London on a lecture tour and met Marconi, who was conducting wireless experiments for the British post office. In 1897, Marconi established the radio station at Niton, Isle of Wight, England. In 1897, Tesla applied for two key radio patents in the USA. Those two patents were issued in early 1900. In 1898, Marconi opened a radio factory in Hall Street, Chelmsford, England, employing around 50 people. In 1899, Bose announced his invention of the "iron-mercury-iron coherer with telephone detector" in a paper presented at Royal Society, London.

Complete theory

Based on the experimental work of Faraday and other physicists, James Clerk Maxwell in 1864 developed the theory of electromagnetism that predicted the existence of electromagnetic waves, which include radio waves. 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.

Innovations and laboratory experiments

Main article: Wireless telegraphy

Hughes

In 1879, during experiments with his induction balance, David E. Hughes transmitted signals which he attributed to electromagnetic waves. Hughes stated that he found that he was at times unable to obtain a perfect balance in the instrument, through an apparent want of insulation in the coils, but that further investigation had shown the real cause to be a loose contact or microphonic joint set up in some portion of the circuit. He therefore applied the microphone in the circuit, and found that a sound was produced in the telephone receiver whether the microphone was placed directly in the circuit or independently at a distance of several feet from the coils through which an intermittent current was passing. This he found to be due to induced currents set up in the primary coil of the induction balance. He soon found that when an interrupted current was sent through any coil, a microphonic receiver placed anywhere in the room was affected at every interruption of the primary circuit.

Hughes used his apparatus to transmit over a few hundred yards, using a transmitter controlled by clockwork and a receiver using his carbon detector. Investigations were made to determine the best form of receiver, and Professor Hughes found that all microphonic joints were extremely sensitive. Those formed of hard carbon, such as coke, or a combination of a piece of coke, resting upon a bright steel contact, were both sensitive and self restoring, but a loose contact between metals, while equally sensitive, would cohere, or remain in full contact after the passage of an electric wave. He soon found that while an invisible spark would produce a current in the microphonic contacts, a far more powerful effect could be produced by inserting a weak battery in the receiving circuit, when the microphonic joint acted as a relay by increasing or diminishing the resistance at the contact, owing to the action of the electric waves transmitted through the air.

In 1870 and 1880 these results were shown to several well-known physicists, including Sir George Gabriel Stokes. Experiments on aerial transmission were exhibited over distances extending up to nearly 500 yards, when the signals could no longer be distinguished with certainty. Sir George Stokes, considering that these effects were simply those of ordinary electromagnetic induction, did not accept Professor Hughes's suggestion that they were due to electric waves transmitted through the air, and unfortunately this failure to convince Sir George and other physicists to whom the phenomena were shown led Professor Hughes to postpone making them generally known until he was prepared with a more complete demonstration of the existence of these waves.

Hughes' contemporaries claimed that the detected effects were due to electromagnetic induction although there have been later claims that he did, in fact, transmit and receive electromagnetic waves. While Professor Hughes was continuing his investigations in this direction, Hertz's papers were published, and then he thought it too late to bring forward these earlier experiments.

Hertz

Heinrich Rudolf Hertz was the experimental physicist who confirmed Maxwell's work in the laboratory. From 1886 to 1888 inclusive, in his UHF experiments, he transmitted and received radio waves over short distances and showed that the properties of radio waves were consistent with Maxwell’s electromagnetic theory. He demonstrated that radio radiation had all the properties of waves (now called electromagnetic radiation), and discovered that the electromagnetic equations could be reformulated into a partial differential equation called the wave equation.

Hertz used the damped oscillating currents in a dipole antenna, triggered by a high-voltage electrical capacitive spark discharge, as his source of radio waves. His detector in some experiments was another dipole antenna connected to a narrow spark gap. A small spark in this gap signified detection of the radio waves. When he added cylindrical reflectors behind his dipole antennas, Hertz could detect radio waves about 20 metres from the transmitter in his laboratory. He did not try to transmit further because he wanted to prove electromagnetic theory, not to develop wireless communications.

In the collection of physical instruments at the Technical High School at Karlsruhe (where these researches were carried out), Hertz had found and used for lecture purposes a pair of so-called Eiess spirals or Knochenhauer spirals. Hertz had been surprised to find that it was not necessary to discharge large batteries through one of these spirals in order to obtain sparks in the other; that small Leyden jars amply sufficed for this purpose, and that even the discharge of a small induction coil would do, provided it had to spring across a spark gap. In altering the conditions Hertz came upon the phenomenon of side-sparks, which formed the starting point of his research. At first Hertz thought the electrical disturbances would be too turbulent and irregular to be of any further use, but when he had discovered the existence of a neutral point in the middle of a side-conductor, and therefore of a clear and orderly phenomenon, he felt convinced that the problem of the Berlin Academy was now capable of solution. His ambition at the time did not go further than this. Hertz's conviction was naturally strengthened by finding that the oscillations with which he had to deal were regular.

1887 experimental setup of Hertz's apparatus.

Hertz’s setup for a source and detector of radio waves (then called Hertzian waves in his honor) was the first intentional and unequivocal transmission and reception of radio waves through free space. The first of the papers published ("On Very Rapid Electric Oscillations") gives, generally in the actual order of time, the course of the investigation as far as it was carried out up to the end of the year 1886 and the beginning of 1887.

Hertz, though, did not devise a system for actual general use nor describe the application of the technology and seemed uninterested in the practical importance of his experiments. He stated that "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."

Asked about the ramifications of his discoveries, Hertz replied, "Nothing, I guess." Hertz also stated, "I do not think that the wireless waves I have discovered will have any practical application." Hertz died in 1894, so the art of radio was left to others to implement into a practical form.

Branly

In 1890, Édouard Branly demonstrated what he called the "radio-conductor," which Lodge later renamed the coherer, the first sensitive device for detecting radio waves. Shortly after the experiments of Hertz, Dr. 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.

Prof. 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. 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 1895-96 Poppoff and others utilized the coherer to show the existence of atmospheric electricity, using for the purpose a vertical wire attached to the coherer.

Tesla

Basic form of Nikola Tesla's Spark-gap transmitter
Source: H. S. Norrie, "Induction coils: how to make, use, and repair them". Norman H. Schneider, 1907, 4th edition, New York.

Around July 1891, Nikola Tesla constructed various apparatus that produced between 15,000 to 18,000 cycles per second. Transmission and radiation of radio frequency energy was a feature exhibited in the experiments by Tesla which he proposed might be used for the telecommunication of information.

After 1892, Tesla delivered a widely reported presentation before the Institution of Electrical Engineers of London in which he suggested that messages could be transmitted without wires. Later, a variety of Tesla's radio frequency systems were demonstrated during another widely known lecture, presented to meetings of the National Electric Light Association in St. Louis, Missouri and the Franklin Institute in Philadelphia.

Between 1895 and 1899, Tesla claimed to have received wireless signals transmitted over long distances, although there is no independent evidence to support this.

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. In his early activities, Bose ignited gunpowder and rang a bell at a distance using electromagnetic waves, showing independently that communication signals can be sent without using wires. 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."

Bose in 1895, at the public lecture in Calcutta, demonstrated the ability of the electric rays to travel from the lectureroom, and through an intervening room and passage, to a third room 75 feet 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 20-foot pole being put in connection with the radiator and a similar one with the receiving apparatus.

Encouraged by this success, he not only went on signalling through the College but planned to fix one of these poles on the roof of his house and the other on the Presidency College a mile away; but he left for England before effecting this. 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.

Bose was not interested in the commercial exploitation of the experiment's transmitter. And subsequently, 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. But as to this he was determined from the first. He did not try to file patent protection for sending signals.

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 developenmnt of radio.

Braun

In 1897 Ferdinand Braun joined the line of wireless pioneers. His 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. Wireless telegraphy claimed Dr. Braun's full attention in 1898, and for many years after that he applied himself almost exclusively to the task of solving its problems. Dr. 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 losses swinging between coil and Leyden Jars. And by means of inductive antenna coupling the radiator was better matched to the generator. The resultant stronger and less bandwidth consuming signals bridged a much longer distance.

The Nobel Prize awarded to Braun in 1909 depicts this design. Braun experimented at first at the University of Strassbourg. Not before long he bridged a distance of 42 km to the city of Mutzing. In spring 1899 Braun, accompanied by his colleagues Cantor and Zenneck, went to Cuxhaven to continue their experiments at the North Sea. 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.

Early commercial exploitation

Main article: History of broadcasting

Later Developers

Alexander Stepanovich Popov Guglielmo Marconi

Reginald Fessenden

Popov

Beginning in the early 1890s, Alexander Stepanovich 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. He presented it to the Russian Physical and Chemical Society on May 7, 1895 — the day has been celebrated in the Russian Federation as "Radio Day". 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.

In the years that followed, Popov worked on his design. 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 away at Kymi (nowadays Kotka) on the Finnish coast.

Marconi

Guglielmo Marconi is said to have read, while on vacation in 1894, about the experiments that Hertz did in the 1880s and 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 a mile at the end of 1895.

By 1896, Marconi introduced to the public a device in London, asserting it was his invention. Despite Marconi's statements to the contrary, though, the apparatus resembles Tesla's descriptions in the widely translated articles. Marconi's later practical four-tuned system was pre-dated by N. Tesla, Oliver Lodge, and J. S. Stone. He filed a patent on his system with the British Patent Office on June 2, 1896.

Marconi's reputation is largely based on the making of his law, and these accomplishments in radio communications and commercializing a practical system. His 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.

Transatlantic transmissions

In 1901, Marconi claimed to have received daytime transatlantic radio frequency signals at a wavelength of 366 metres (820 kHz). 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. The Poldhu to Newfoundland transmission claim has been criticized. 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. The message received was the Morse letter 'S' - three dots. Bradford has recently contested this, however, based on theoretical work as well as a reenactment of the experiment; 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.

In 1902, Marconi transmitted from his station in Glace Bay, Nova Scotia, Canada across the Atlantic, and on 18 January 1903 a Marconi station built in Wellfleet, Massachusetts in 1901 sent a message of greetings from Theodore Roosevelt, the President of the United States, to King Edward VII of the United Kingdom, marking the first transatlantic radio transmission originating in the United States.

Marconi would later found the Marconi Company and would jointly receive the 1909 Nobel Prize in Physics with Karl Ferdinand Braun for contributions to the existing radio sciences.

20th century patents

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.

Fessenden

In late 1886, 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. By 1900, Fessenden was working for the United States Weather Bureau where he evolved the heterodyne principle where two signals combined produce a third audible tone. While there, Fessenden, experimenting with a high-frequency spark transmitter, successfully transmitted speech on December 23, 1900 over a distance of about 1.6 kilometers (one mile), the first audio radio transmission.

Developers of radio

Name	Pro	Con	Earliest transmission
Bose	Researched coherers. Transmitted microwaves over distance of 75 feet in 1895. Had transmitted microwaves nearly a mile by 1896.	Did not pursue commercialization.	1895
Braun	Invented closed circuit and coupled coils for transmitters.	Did not recognize the significance when Hertz published his findings in 1888.	1897
DeForest	Developed the triode amplifier and the Audion tube.	Late upon beginning research into space telegraphy.	1896
Fessenden	First audio transmission by radio (1900). Also, the first two-way transatlantic radio transmission (1906), and the first radio broadcast of entertainment and music (1906)	Not the first to transmit Morse code.	1900
Henry	Henry detected electromagnetic effects at a distance of two hundred feet.	He was focused on wired telegraphy and researched self-inductance.	1829
Hertz	By 1888, Hertz had studied and understood the work of Maxwell and, by design, produced the first clear and undisputed experimental evidence for the transmission and reception of radio waves.	Hertz took this work no further, did not exploit it commercially, and famously did not consider it useful.	1888
Hughes	In 1879, Hughes began research into radio waves. He noticed electrical interference in an induction balance he was working with. The observed effect was due to radio waves and he discovered and improved the coherer.	Hughes was not trying to design equipment for wireless communication. His discovery was taken no further.	1879
Lodge	On 14 August 1894 Lodge sent a radio message in Morse code.	Did not pursue further.	1894
Loomis	In 1872, received a patent for a "wireless telegraph". Patent utilizes atmospheric electricity to eliminate the overhead wire used by the existing telegraph systems.	His patent U.S. patent 129,971 was for the purpose of receiving and imparting atmospheric electricity.	None (n/a)
Marconi	In summer 1895, Marconi sent signals 1.5 km. In 1896, applied for British patent protection for a radio system. In 1900, he was granted British patent No. 12,039. Transmission over 6 km in March and May 1897. Transatlantic transmission on 12 December 1901. Transmission over 3,378 km in February 1902. Transatlantic message on 17 December 1902. In 1897 Marconi founded "Wireless Telegraph and Signal Company" and exploited the "Marconi System" of radio commercially. He shared the 1909 Nobel Prize in Physics with Karl Ferdinand Braun, "in recognition of their contributions to the development of wireless telegraphy".	His 1901 transatlantic transmission is disputed. Many of Marconi's system components were developed by others. Oliver Lodge claimed British patent of 1900 to contain his own ideas which he failed to patent.	1895
Maxwell	By 1864 Maxwell had become the first person to demonstrate theoretically the existence of radio (electromagnetic) waves, which are used by all radio equipment.	Maxwell did not generate or receive radio waves.	None (n/a)
Popov	Confirmed laboratory demonstration of radio on 7 May 1895. In 1896 or 1897 publicly demonstrated the sending of a signal 250 m between two campus buildings. By 1900 he had reliable communications over 25 miles.	Was not the first to send signals significant distances.	1895
Tesla	Tesla developed means to reliably produce radio frequency currents. In 1891 and afterwards, lectured about high-frequency devices and demonstrated devices using power without the use of wires. Referring to a demonstration of his wireless equipment in 1893 the IEE said "the apparatus that he employed contained all the elements of spark and continuous wave that were incorporated into radio transmitters before the advent of the vacuum tube". By 1895, stated that he had the ability to transmit signals under 50 miles. In 1897, Tesla applied for protection for the radio arts. In 1900 Tesla was granted U.S. patent 645,576 and U.S. patent 649,621. In 1898, demonstrated a radio controlled boat in Madison Square Garden that allowed secure communication between transmitter and receiver. After 1915, assisted the Telefunken engineers in constructing the Telefunken Wireless Station (the "Arco-Slaby system") in Sayville, Long Island.	No independently confirmed radio transmissions before 1898. Primarily because of financial difficulties, Tesla never completed his "worldwide wireless system". The Wardenclyffe Tower transceiver that he began at Shoreham on Long Island, New York was eventually torn down.	1891
Ward	Ward was the first person to be granted a US patent relating to wireless telegraphy.	His patent U.S. patent 126,356 was for the purpose of receiving and imparting natural electricity.	None (n/a)
Cervera	He was the first person to be granted a patent regarding a radiotelephonic system in 1899.	His activities on this field ceased suddenly, the reasons for which are unclear to this day.	1899

Timeline

Main article: Timeline of radio

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

See also

People

Edwin Howard Armstrong, John Stone Stone, Ernst Alexanderson, Reginald Fessenden, Oliver Lodge, 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 A.W.A. (Antique Wireless Association) Review, Vol. 1, 1986, pp. 18–41.

External links

• "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.
• 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
• 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
• "Wireless telegraphy", The Encyclopaedia Britannica. (1922). London: Encyclopædia Britannica.
• Mazzotto, D., & Bottone, S. R. (1906). Wireless telegraphy and telephony. London: Whittaker & Co.
• Fleming, J. A. (1908). The principles of electric wave telegraphy. London: New York and Co.
• Murray, J. E. (1907). A handbook of wireless telegraphy. New York: D. Van Nostrand Co.; [etc.]
• 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.
• Massie, W. W., & Underhill, C. R. (1911). Wireless telegraphy and telephony popularly explained. New York: D. Van Nostrand.
• Sewall, C. H. (1904). Wireless telegraphy: its origins, development, inventions, and apparatus. New York: D. Van Nostrand.
• Collins, A. F. (1905). Wireless telegraphy; its history, theory and practice. New York: McGraw Pub.
• Fahie, J. J. (1900). A history of wireless telegraphy, 1838-1899: including some bare-wire proposals for subaqueous telegraphs. Edinburgh: W. Blackwood and Sons.
• Colby, F. M., Williams, T., & Wade, H. T. (1930). "Wireless Telegraphy", The New international encyclopaedia. New York: Dodd, Mead and Co.
• 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.
• Stanley, R. (1919). Text-book on wireless telegraphy. London: Longmans, Green.
• Thompson, S. P. (1915). Elementary lessons in electricity and magnetism. New York: Macmillan
• Telegraphing across space, Electric wave method. The Electrical engineer. (1884). London: Biggs & Co.
• Simmons, H. H. (1908). "Wireless telegraphy", Outlines of electrical engineering. London: Cassell and Co.
• Bottone, S. R. (1910). Wireless telegraphy and Hertzian waves. London: Whittaker & Co.
• Erskine-Murray, J. (1909). A handbook of wireless telegraphy: its theory and practice, for the use of electrical engineers, students, and operators. New York: Van Nostrand.
• American Institute of Electrical Engineers. (1884). "Wireless Telephony — By R. A. Fessenden (Illustrated.)", Transactions of the American Institute of Electrical Engineers. New York: American Institute of Electrical Engineers.
• 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.
• Katz, Randy H., "Look Ma, No Wires": Marconi and the Invention of Radio". History of Communications Infrastructures.
• American Institute of Electrical Engineers. (1884). 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. (1914). Text book on wireless telegraphy. London: Longmans, Green.
• Comparative Study of the Hertz, Marconi and Tesla Low-Frequency Wireless Systems
• Timeline: First Thirty Years of Radio, 1895-1925
• 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.