Development of radio
Formative "wireless" methods
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.[citation needed]
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.[citation needed]
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.
Claims have been made[citation needed] 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.
In 1878, David E. Hughes noticed that sparks could be heard in a telephone receiver when experimenting with his carbon microphone.[13] He developed this carbon-based detector further and eventually could detect signals over a few hundred yards.[14] He demonstrated his discovery to the Royal Society in 1880, but was told it was merely induction, and therefore abandoned further research, although there have been later claims that he did, in fact, transmit and receive electromagnetic waves.[15][16] 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.[14]
Early radio development
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The key invention for the beginning of "wireless transmission of data using the entire frequency spectrum", known as thespark-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.
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" [17][18] 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.
Early radio's origin and development of old, or damped wave-coherer, methods began with Joseph Henry.[19] He was the first (1838–42) to produce high frequency electrical oscillations, and to point out and experimentally demonstrate that the discharge of a condenser is under certain conditions 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".[20] This view was also later adopted by Helmholz,[21] but the mathematical demonstration of this fact was first given by Lord Kelvin in his paper on "Transient Electric Currents".[22][23]
In 1870 the German physicist Wilhelm von Bezold discovered and experimentally demonstrated the fact that the advancing and reflected oscillations produced in conductors by a condenser discharge gave rise to interference phenomena.[24][25]Professors Elihu Thomson and E. J. Houston in 1876 made a number of experiments and observations on high frequency oscillatory discharges.[26] In 1883 G. F. Fitzgerald suggested[27] at a British Association meeting that electromagnetic waves could be generated by the discharge of a condenser, but the suggestion was not followed up, possibly because no means was known for detecting the waves.[23]
Hertz[28] discovered a method of detecting such waves by means of a minute spark-gap and, before March 30, 1888, had concluded his remarkable series of researches in which for the first time electromagnetic waves were actually produced by a spark-gap and radiating conductor and received and detected at a distance by a tuned receiving circuit. Hertz changed the frequency of his radiated waves by altering the inductance or capacity of his radiating conductor or antenna, and reflected and focused the electromagnetic waves, thus demonstrating the correctness of Maxwell's electromagnetic theory of light.[23]After Hertz, Sir William Crookes discussed the matter of wireless in some detail.[29] Professor Amos Emerson Dolbear also suggested the same thing.[30]
Hertz
Between 1886 and 1888, Heinrich Rudolf Hertz[31] studied Maxwell's theory and validated it through experiment.[32]Concerning wireless telegraphy, he demonstrated the transmission and reception of the electromagnetic waves predicted by Maxwell and intentionally transmitted and received radio. Hertz changed the frequency of his radiated waves by altering the inductance or capacity of his radiating conductor or antenna, and reflected and focused the electromagnetic waves, thus demonstrating the correctness of Maxwell's electromagnetic theory of light.[23] Famously, he saw no practical use for his discovery.
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 (now called electromagnetic radiation) 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’s setup for a source and detector of radio waves (then called Hertzian waves[33] in his honor) was the first intentional and unequivocal transmission and reception of radio waves through free space.[34] 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.[35]
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. 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."[36] Hertz died in 1894, and the art of radio was left to others to implement into a practical form.
Branly
In 1890, Édouard Branly[37][38][39] demonstrated what he later called the "radio-conductor,"[40] which Lodge in 1893 named the coherer, the first sensitive device for detecting radio waves.[41] 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.[42]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.[43] 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.[44] The coherer, however, was not sensitive enough to be used reliably as radio developed.[45]
Tesla
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In 1891, Nikola Tesla began his research into radio. Around July 1891, Tesla developed various alternator apparatus that produced 15,000 cycles per second.[47][48][49][50] In 1892 he delivered a lecture called "Experiments with Alternate Currents of High Potential and High Frequency" before the Institution of Electrical Engineers of London, in which he suggested that messages could be transmitted without wires. He repeated this presentation at the Royal Institution[51] and at the Société Française de Physique in Paris.[51] Tesla realized he gained, by the use of very high frequencies, many advantages in his experiments, such as the possibilities of working with one lead and of doing away with the leading-in wire. In transmitting impulses through conductors, he dealt with high pressure and high flow, in the ordinary interpretation of these terms. Towards the end of the lecture, he proposed that sending over the wire current vibrations of very high frequencies at enormous distance without affecting greatly the character of the vibrations and that telephony could be rendered practicable across the Atlantic. He also proposed transmission through the Earth.[52] Tesla captured the attention of the whole scientific world by his fascinating experiments on high frequency electric currents. He stimulated the scientific imagination of others as well as displayed his own, and created a widespread interest in his brilliant demonstrations.[53]Accordingly there are seven elements in the complete oscillation-producing appliance, which are as follows:[54]
- The induction coil transformer or source of electromotive force.
- The condenser.
- The discharger or spark balls.
- The arc quenching inductances.
- The oscillation transformer.
- The adjustable inductance for varying the period.
- The controller or key in the primary circuit of the coil or transformer.
These several elements have each to be considered separately with reference to their best practical forms for various purposes. When the key is closed, and the apparatus in operation, there are trains of intermittent electrical oscillations set up in the circuit, and if the terminals of the secondary circuit of the oscillation transformer are near together, there is high potential high frequency oscillatory sparks passing between them. The above-described apparatus in a typical form is generally called a Tesla apparatus for the production of high frequency electric currents.[54]
"On Light and Other High Frequency Phenomena" |
In 1893, at St. Louis, Missouri, Tesla gave a public demonstration, "On Light and Other High Frequency Phenomena",[55]of wireless communication. Addressing the Franklin Institute in Philadelphia,[56] he described in detail the principles of early radio communication. The lecture 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. The lecture delivered before the Franklin Institute, at Philadelphia, occurred on February 24, 1893. The variety of Tesla's radio frequency systems were again demonstrated during when he presented to meetings of the National Electric Light Association, at St. Louis, on March I, 1893. Afterward, the principle of radio communication (sending signals through space to receivers) was publicized widely from Tesla's experiments and demonstrations. On August 25, 1893, Tesla delivered the lecture "Mechanical and Electrical Oscillators",[57] before the International Electrical Congress, in the hall adjoining the Agricultural Building, at the World's Fair, Chicago.[58]
The high-frequency phenomena which Tesla first developed and displayed had scientific rather than practical interest; but Tesla called attention to the fact that by taking the Tesla oscillator,[59][60][61] grounding one side of it and connecting the other to an insulated body of large surface, it should be possible to transmit electric oscillations to a great distance, and to communicate intelligence in this way to other oscillators in sympathetic resonance therewith. This was going far toward the invention of radio-telegraphy as known in the early 20th century, as stated by the Electrical World in 1917.[62][63]
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.[64][65] The Tesla method was mentioned in New York in 1897.[66][67][68] In Buffalo, New York, he referred to devised means for transmission of electromotive forces, much higher than practical with ordinary apparatus, and the transmission of power from station to station without the employment of any connecting wire. Tesla later, on April 6, 1897, explained his methods of the transformation of electrical energy by oscillatory condenser discharges in his lecture "The stream of Lenard and Roentgen and novel apparatus for their production".[69][70]He demonstrated his subject by a fine array of improved apparatus, in which a few feet of wire were made as efficient as miles under old systems.[69]
In 1894, T. C. Martin published "The Inventions, Researches and Writings of Nikola Tesla", detailing the work of Tesla in the previous years. Various scientists, inventors, and experimenters began to investigate wireless methods. Telsa's work contained coupled oscillation circuits having capacity and inductance in series.[71][72][73] In 1897, Tesla applied for two key United States radio patents,[74] US 645576, first radio system patent, and (later subdivided into) US 649621, for protection of his interests of the radio arts.[75] Tesla also developed sensitive electromagnetic receivers,[76][77][78] that were unlike the less responsive coherers later used by other early experimenters.
Shortly thereafter, he began to develop wireless remote control devices. In 1898, he demonstrated a radio controlled boat in Madison Square Garden that allowedsecure communication[79][80] between transmitter and receiver.[81] Between 1895 and 1897, Tesla received wireless signals transmitted via short distances in his lectures. Between 1897 and the first decade of the 1900s, he transmitted over medium ranges.[citation needed] Tesla had predicted that not only would intelligible signals be transmitted over long distances without wires, but electric power as well.[82] He later published articles, such as "The True Wireless",[83] and "The Transmission of Electric Energy Without Wires",[84] concerning the World Wireless System research.
de Moura
Roberto Landell de Moura, a Brazilian priest and scientist, went to Rome in 1878 and studied at the South American College[85] and Pontifical Gregorian University, where he studied physics and chemistry. He completed his clerical training in Rome, graduating in theology and was ordained priest in 1886. In Rome, he started studying physics and electricity. When he returned to Brazil, he conducted experiments in wireless in Campinas and São Paulo (1892–1893).[86][87] The experiments of de Moura were performed in the presence of the English Vice Consul S. Paul, Percy Parmenter, Charles Lupton, and other persons of high social position.[citation needed] Upon observing the experiments, Rodriguez Botet, giving news of the trials, said he was not far from the moment of the consecration of Landell as an author of radio discoveries. The wireless telephony is reputed the most important discoveries of Landell. De Moura did later pursue and receive several patents on wireless technology.[88][89] He would later obtain U.S. Patent 775,337 for a wireless telephone.
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 SirOliver Lodge, entitled "Experiments On The Discharge Of Leyden Jars" (1891).[90][91] On June, 1, 1894, Oliver Lodge at the Royal Institution lectures, delivered "The Work of Hertz and Some of His Successors".[92] Two years after Tesla's high potential and high frequency lecture and five years after Hertz's signals, Lodge performed transmission on August 14, 1894.[9] This was a year before Marconi's initial experiments. Lodge did this at a meeting of the British Association for the Advancement of Science at Oxford University.[93][94] Also in 1894, Lodge would state that Alexander Muirhead clearly foresaw the telegraphic importance of the transmission of transverse Hertzian waves.[91] A convenient method of establishing stationary electric waves on wires is one which generally attribute to Ernst Lecher,[95] and call the Lecher arrangement.[91] As a matter of fact, it originated with Lodge and Hertz, whilst Edouard Sarasin and Lucien de la Rive gave it an improved form.[91][96]
On that day in August 1894, Lodge demonstrated the reception of Morse code signalling via radio waves using a "coherer". He later improves Branly's coherer by adding a "trembler" which dislodged clumped filings,[97] thus restoring the device's sensitivity.[98] In August 1898 he got U.S. Patent 609,154, "Electric Telegraphy", that made wireless signals usingRuhmkorff coils or Tesla coils for the transmitter and a Branly coherer for the detector. This patent was utilizing the concept of "syntonic" tuning. In 1912 Lodge sold the patent to Marconi.
| Lodge 1894 lecture |
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Lodge's June 1, 1894 lecture before the Royal Institution.[99]described among other things the following:[100]
In this lecture, Lodge stated that in his estimate the apparatus used would respond to signals at a distance of .5 miles (0.80 km). |
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.[43]
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[106] 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.[107]
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.[108] Bose ignited gunpowder and rang a bell at a distance using electromagnetic waves,[109] proving that communication signals can be sent without using wires. He sent and received radio waves over 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.[110][111] 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.[112]
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.[112] 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.[112]
In 1899, Bose announced the development of an "iron-mercury-iron coherer with telephone detector" in a paper presented at the Royal Society, London.[113] 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.[114]
Rutherford
The New Zealander Ernest Rutherford, 1st Baron Rutherford of Nelson contributed to 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 maintaininglighthouses 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 via his electromagnetic receiver over a distance of several hundred meters. The hysteresis magnetic detector[115] invented by Rutherford, and described by him in 1897,[116] was used to determine the characteristics of electromagnetic waves, the ends of the little solenoid of the detector being attached to the mercury cups of the slider.[117] The development, though, of wireless technology was left for others, as Rutherford continued purely scientific research. J. J. Thomson realized that Rutherford was a researcher of ability and invited him to join in a study of the electrical conduction of gases.
Braun
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 Strassbourg. Braun had written extensively on wireless subjects and was well known through his many contributions to the Electrician and other scientific journals.[118] 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.[119]
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[120] 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.[121] 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.[122] 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, owing to the fact that 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.[121] 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.[121][123] 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.[121][124] 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.
Later radio development
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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.[126][127] Afterward, he worked on his wireless designs.[128][129][130] Popov conducted experiments along the lines of Hertz's research. In 1894-95 he built his firstradio receiver, an improved version of coherer-based design by Oliver Lodge. In 1895, he built a coherer. Popov[131]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.[132]
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.[133]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.[134] 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.[135][136]
In 1895-96 Popov[137] and others utilized the coherer to show the existence of atmospheric electricity, using for the purpose a vertical wire attached to the coherer.[43] 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.[138] 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.[citation needed]
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."[citation needed] Also 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 battleshipGeneral-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.
Baviera
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.[139] 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.[140] In 1894, SirWilliam Preece deliver a paper to the Royal Institution in London on electric signalling without wires.[141][142][143] In 1894 at the Royal Institution lectures, Lodge delivers "The Work of Hertz and Some of His Successors".[92] 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.[144] It was at this time that Marconi began to understand that radio waves could be used for wireless communications.[145] 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 mile (1.6 km) at the end of 1895.[146]
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 his research, demonstrations and patents.[147][148] 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 earliest system with the British Patent Office on June 2, 1896.
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 (primarily Tesla) 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 delievers "Signalling through Space without Wires".[149][150] 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.[151]
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In 1896, Bose went to London on a lecture tour and met Marconi, who was conducting wireless experiments for the British post office. TheMarconi 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).[154] Marconi's reputation is largely based on the making of his law (1897), and other accomplishments in radio communications and commercializing a practical system.
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[155] of the Post Office pattern.[156][157] 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.[158] 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.[159] Electric wave telegraphy had the advantages as follows:[160]
- Transmission worked as well by night as by day, and in bad weather, fogs, or storms, as well as in fair weather; provided that the proper insulation of the aerial wire or elevated conductor was maintained.
- In certain electrical conditions of the atmosphere, and during thunderstorms, some difficulty was usually found in working, owing to the atmospheric discharges affecting the sensitive tube, and therefore making stray marks on the Morse tape of the printer, but seldom sufficient to interrupt communication altogether.
- The interposition of high hills, trees, or the curvature of the earth did not prevent communication, though slightly affecting the power required. It worked particularly well over sea surface, and between ships and shore stations.
- The apparatus could be set up and handled by any ordinary telegraphist, and the record was made on paper strip in the usual Morse code.
- Transmission easily covered distances far beyond those feasible or attained by other systems of wireless telegraphy.
- Lastly, the apparatus required was by no means costly, and, with the exception of the mast required for upholding the aerial wire, it occupied but little space, and was particularly adapted for use on board ship.
The Haven Hotel station and Wireless Telegraph Mast was where much of Marconi's research work on wireless telegraphy was carried out after 1898.[160] In 1899, he transmitted messages across the English Channel. Also in 1899, Marconi delivered "Wireless Telegraphy" to the Institution of Electrical Engineers.[161] 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.[162] 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.[163] The Marconi Company was renamed Marconi's Wireless Telegraph Company in 1900.
In 1901, Marconi claimed to have received daytime transatlantic radio frequency signals at a wavelength of 366 metres (820 kHz).[165][166][167] 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 a 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 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.[166][167] The distance between the two points was about 3,500 kilometres (2,200 mi).
The Poldhu to Newfoundland transmission claim has been criticized.[168] 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.[169] 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.[170] In this period, a particular electromagnetic receiver, called the Marconi magnetic detector[171] or hysteresis magnetic detector,[115] 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.[172][173] 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.[174]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
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."[175] 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.[176]
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 inChelmsford.[177]
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,[178]establishing the first transatlantic radio service,[170] 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 RE11,913 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. In 1943, a lawsuit regarding Marconi's early United States radio patents were resolved by the United States Supreme Court, who overturned most of these.
The United States Navy Board had issued a 1899 report on the results of investigations of the Marconi system of wireless telegraphy.[179] The report, Notes On The Marconi Wireless Telegraphy[180] was published in full in the Electrician, and from it the following statements concerning the efficiency of the system have been taken:[181] 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. The Board respectfully recommended that the system be given a trial in the United States Navy.[181]
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.[182][183] 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).[184]
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.[185] A complete analysis of Stone's specifications would occupy too much space. Broadly speaking, they may be divided into four classes:[185]
- Those concerned with proposed methods for the achievement of syntonic telegraphy, or the isolation of receiving stations or protection of receivers from the action of vagrant waves.
- Those describing forms of electric wave detector or cymoscope.
- Those covering the construction of various forms of transmitting and receiving circuit, and the production of continuous trains of waves.
- Miscellaneous specifications covering devices proposed for localizing the direction of the arriving waves and other matters.
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.[186] 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.[186] 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.[187] 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.[187] A coherer made on what is called the Stone system[188] 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.[188]
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. Fessenden's Initial United States Patents[189] were U.S. Patent 706,735 and U.S. Patent 706,736and are companion patents. One concerns the methods and the other the devices of the same system.[190] The United States Weather Bureau began, early in 1900, a systematic course of experimentation in Wireless Telegraphy, employing him as a specialist.[191] Fessenden evolved the heterodyne principle here where two signals combined to produce a third audible tone.
In 1900, construction began on a large radio transmitting dynamo was began. 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).[191] A dynamo 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.[192]
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. He also declared that syntony was not safely selecting, but that he had discovered several methods which were.[191] In an interview with a New York Journal correspondent, Fessenden stated in his early apparatus that he did not use any air transformer at the sending end, nor concentric cylinder for emitters and antennae.[191][193] He used capacity, but that it was 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. His apparatus was of solid metal,[194] and, according to Fessenden, acted under a physical law entirely different from that which governs the receiving devices of Marconi. Fessenden asserted that he had paid particular attention to selective and multiplex systems, and was well satisfied with the results in that direction.[191] On August 12, 1902, there were issued to Fessenden thirteen patents on various methods, devices, and systems for signaling without wires.[191] These patents involved many new principles, the chef-d'eeuvre of which was a method for distributing capacity and inductanceinstead of localizing these coefficients of the oscillator as in previous systems.[186]
By the summer of 1906, a machine producing 50 kilohertz was installed at the Brant Rock station, and in the fall of 1906, the electric alternating dynamo was working regularly at 75 kilohertz, with an output of 0.5 kW.[192] Fessenden[195] used this for wireless telephoning toPlymouth, a distance of approximately 11 miles (18 km).[192] In the following year machines were constructed having a frequency of 96 kilohertz[196] 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.[192] He would employ a two-phase high frequency dynamo method[197] and the continuous production of waves[198] with changing constants of sending circuit.[192][199] Fessenden would also use duplex and multiplex commutator methods.[200] On Dec. 11, 1906, operation of the wireless transmission in conjunction with the wire lines took place.[201][192] In July 1907 the range was considerably extended and speech was successfully transmitted between Brant Rock and Jamaica, Long Island, a distance of nearly 200 miles (320 km), in daylight and mostly over land,[202] the mast at Jamaica being approximately 180 feet (55 m) high.[192]
Fleming
 | This section requires expansion. |
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.[203][204] This "Fleming Valve" was much used as a receiver for long-distance wireless on account of its sensitivity. It also had another 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.[205] For this reason it was the detector par excellence for large antenna or high-power stations.
Fleming[206] recognized the use of the rectifying properties of a wireless tube for the indication of high frequency oscillations, and used it as aelectromagnetic detector.[207] On November 7, 1905, he would be granted U.S. Patent 803,684. Marconi used this device as a radio detector, also.[when?]
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.[208] This invention was the first vacuum tube. Fleming's diode was used in radio receivers for many decades afterward, until it was superseded by solid state electronic technology more than 50 years later.
De Forest
| This section requires expansion. |
Lee De Forest[209][210][211] 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).[212][213] 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.[214]
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 the Great War, 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.[214]
Radio developer comparison
Formative stage
| Name | Pro | Con | Earliest transmission |
|---|---|---|---|
| Henry | Henry detected electromagnetic effects at a distance of two hundred feet.[215][216][217] | He was focused on wired telegraphy and researched self-inductance.[218][219] | 1829[220] |
| Hughes | In 1879, Hughes began research into radio waves. He noticed electrical interference in an induction balance he was working with.[221][222] The observed effect was due to radio waves and he discovered and improved the coherer.[223] | Hughes was not trying to design equipment for wireless communication. His discovery was taken no further.[223] | 1879[223][224] |
| 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.[225][226] | Maxwell did not generate or receive radio waves.[227] | None (n/a) |
Early developers
| Name | Pro | Con | Earliest transmission |
|---|---|---|---|
| Branly | Researched coherers. In 1890 Branly showed that such a tube would respond to sparks produced at a distance from it.[228] | Others would expound upon the idea of using such a tube.[229][230] | |
| Bose | Researched coherers.[231][232] Transmitted microwaves over distance of 75 feet in 1895.[233][234] Had transmitted microwaves nearly a mile by 1896.[235][236][237] | Did not pursue commercialization.[238][239] | 1895[citation needed] |
| de Moura | Early Transmission (c. 1893) Publicly demonstrated a radio broadcast of the human voice (1900) | Exhibition of the his apparatus occurred in 1900 | 1900[citation needed] |
| Braun[240] | Invented closed circuit and coupled coils for transmitters. | Did not recognize the significance when Hertz published his findings in 1888. | 1897[citation needed] |
| 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[citation needed] |
| Lodge | Awarded the "syntonic" (or tuning) US Patent | ||
| Rutherford | Developed sensitive apparatus until he could detect electromagnetic waves over a distance of several hundred meters. | ||
| Tesla | Early Transmission (1893) Tesla developed means to reliably produce radio frequency currents.[241] In 1891 and afterwards, lectured about high-frequency devices and demonstrated devices using power without the use of wires.[64][65][242][243][244][245] 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".[246] By 1895, stated that he had the ability to transmit signals under 50 miles.[247][248][249][250][251] In 1897, Tesla applied for protection for the radio arts.[75] In 1900 Tesla was grantedU.S. Patent 645,576 "System of Transmission of Electrical Energy", (March 20, 1900; filed Sept. 2, 1897) and U.S. Patent 649,621 "Apparatus for Transmission of Electrical Energy" (May 15, 1900; filed February 19, 1900). In 1898, demonstrated a radio control and secure communication[79][252] between transmitter and receiver.[253] After 1915, assisted the Telefunken engineers in constructing the Telefunken Wireless Station (the "Arco-Slaby system"[254]) in Sayville, Long Island. | Primarily because of financial difficulties, Tesla never completed his "worldwide wireless system".[255] The Wardenclyffe Tower transceiver that he began atShoreham on Long Island, New York was eventually torn down. | c. 1892 [256][257] |
Later developers
| Name | Pro | Con | Earliest transmission |
|---|---|---|---|
| Baviera | He was the first person to be granted a patent regarding a radiotelephonic system in 1899.[258] | His activities on this field ceased suddenly, the reasons for which are unclear to this day.[259] | 1899[citation needed] |
| DeForest[260] | Developed the triode amplifier and the Audion tube. | Late upon beginning research into space telegraphy. | 1896[261][262] |
| 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) | 1900[citation needed] | |
| Fleming | Known for inventing the first thermionic valve. | ||
| Marconi | In summer 1895, Marconi sent signals 1.5 km.[263] Developed Marconi's Law. 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.[264] Transatlantic transmission on 12 December 1901.[265] Transmission over 3,378 km in February 1902.[266] Transatlantic message on 17 December 1902.[267] In 1897 Marconi founded "Wireless Telegraph and Signal Company"[268] and exploited the "Marconi System"[254][269][270][271] 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".[272] | Many of Marconi's system components were developed by others.[273] According to theProceedings of the United States Naval Institute, the Marconi instruments were tested around 1899 and the tests concerning his wireless system 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".[274] Oliver Lodgeclaimed British patent of 1900 to contain his own ideas which he failed to patent. His 1901 transatlantic transmission is disputed.[168] | 1895[263] |
| Popov | Confirmed laboratory demonstration of radio on 7 May 1895.[133] 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.[275] | 1895[133] | |
| Stone | Influential in developing wireless communication technology Holds dozens of key patents in the field of "space telegraphy". |
Radio invention timeline
Below is a selection of pertinent events and individuals, from 1860 to 1910, related to the development of radio.
