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Invention Of Radio
: ''"Great Radio Controversy" redirects here. For the album by the band Tesla, see'': The Great Radio Controversy. ''This article covers the main arguments about who had what part in the early development of radio. For the general history of radio, see'': History of radio.
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.
[[http://inventors.about.com/od/rstartinventions/a/radio.htm The Invention of Radio] inventors.about.com/od/rstartinventions/a/radio.htm] 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.
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.
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".
Complete theory of electromagnetism
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. He did not transmit or receive radio waves.
Innovations and laboratory experiments
In 1879, during experiments with his induction balance, David E. Hughes transmitted signals which he attributed to electromagnetic waves. Hughes' contemporaries claimed that the detected effects were due to electromagnetic induction. Hughes used his apparatus to transmit over a few hundred yards, using a transmitter controlled by clockwork and a receiver using his carbon detector.
Heinrich Rudolf Hertz was the experimental physicist who confirmed Maxwell's work in the laboratory. Hertz, though, did not devise a system for actual general use nor describe the application of the technology. From 1886 to 1888 inclusive, in his UHF experiments, he showed that the properties of radio waves were consistent with Maxwellâs 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.
Hertzâs setup for a source and detector of radio waves (then called Hertzian waves in his honor), comprised a primitive radio system capable of transmitting and receiving radio waves through free space.
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.
Hertz 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 â we just have these mysterious electromagnetic waves that we cannot see with the naked eye. But they are there''."
[Eugenii Katz, "''[http://chem.ch.huji.ac.il/~eugeniik/history/hertz.htm Heinrich Rudolf Hertz]''". Biographies of Famous Electrochemists and Physicists Contributed to Understanding of Electricity, Biosensors & Bioelectronics.]
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.
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.
["''[http://www.tfcbooks.com/tesla/1893-02-24.htm On Light and Other High Frequency Phenomena]''". Delivered before the Franklin Institute, Philadelphia, February 1893, and before the National Electric Light Association, St. Louis, March 1893.] ["''[http://www.tfcbooks.com/tesla/1892-02-03.htm Experiments with Alternating Currents of High Potential and High Frequency]''". Delivered before the Institution of Electrical Engineers, London, February 1892.]
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. According to the IEEE, "''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''".
["''[http://www.ieee.org/web/aboutus/history_center/biography/tesla.html Nikola Tesla, 1856 - 1943]''". IEEE History Center, IEEE, 2003.] However, "''he almost perversely rejected the notion of transmission by Hertzian waves, which he considered to be wasteful of energy.''"
In November 1894, the Bengali Indian physicist, Jagadish Chandra Bose, demonstrated publicly the use of radio waves in Calcutta, but he was not interested in patenting his work. In 1894, 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 was not interested in the commercial applications of the experiment's transmitter. 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 , "''Detector for electrical disturbances''" (1904), for a specific electromagnetic receiver.
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.
All pioneers working on wireless devices 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 bandwith consuming signals
bridged a much longer distance.
The Nobel Prize awarded to Braun in 1909 depicts this design.
Marconi's Nobel Award shows instead a ship with aerials.
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 24th 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
In 1885, T. A. Edison used a vibrator magnet for induction transmission. In 1888, he deployed a system of signaling on the Lehigh Valley Railroad. In 1892, Edison patented a method using capacitive coupling between elevated terminals ().
Early commercial exploitation
The electromechanical engineer Nikola Tesla, who has been called the ''father of wireless telegraphy'',
[Johnson, R., & Brown, J. H. (1904). "[http://books.google.com/books?id=Ou4UAAAAYAAJ&pg=PT122&source=gbs_search_s Nikola Tesla]", [http://books.google.com/books?id=Ou4UAAAAYAAJ The twentieth century biographical dictionary of notable Americans]. Boston: Biographical Society. (cf., He was called the father of wireless telegraphy, which theory he first described in a lecture before the National Electric Light association at St. Louis, Mo., March, 1893; his ideas being given practical demonstration by Marconi in 1902.)] was one of the first to patent a means to reliably produce radio frequency waves. Tesla's , "''Method of Operating Arc-Lamps''" (March 10, 1891), describes an alternator that produced high-frequency (for that time period) current of around 10,000 hertz. His innovation was suppression of the sound produced by arc lamps that were operated on alternating or pulsating current by using frequencies beyond the range of human hearing.
Early on in his research Tesla used his high voltage resonance transformer â the Tesla coil â in radio-wave propagation experiments. The aerial consisted of a top-loaded electrical conductor that was connected to a high-voltage terminal of the transformer. The opposing high-voltage terminal was grounded. The secondary winding was driven by a primary circuit consisting of a few turns of heavy wire, a capacitor bank, a circuit controller, and a power supply transformer. The launching structure could be operated as an electromagnetic radiator (or "Hertz wave antenna") or a large scale electromagnetic resonator.
Between 1895 and 1899, Tesla claimed to have received wireless signals transmitted over long distances, although there is no independent evidence to support this.
After 1896, the transmitter consisted of an RF alternator and produced undamped (or continuous) waves in the neighborhood of 50,000 Hertz. [Nikola Tesla On His Work With Alternating Currents and Their Application to Wireless Telegraphy, Telephony and Transmission of Power : An Extended Interview. Chapter IV ISBN 1-893817-01-6 (cf., [Counsel] What do you mean by high frequencies?] The receiver consisted of a powerful electromagnet, two large condensers, and a taut steel wire. The wire was placed within the magnetic field, and in conjunction with the condensers formed a tuned circuit.
[Tesla] I mean frequencies of 30,000, 40,000, 50,000, or something like that.
[Counsel] And by means of that machine, you put undamped waves of frequency about 50,000 into that antenna at Houston Street in 1895?
[Tesla] No [with that machine], not in 1895. Late in 1895 the machine was furnished and I began to operate in early 1896. That is when I began to operate.
[Counsel] Then you did this, that I speak of, in 1896?
[Tesla] Yes, from 1896 to 1899, right along.)
In Tesla's own words:
"The popular impression is that my wireless work was begun in 1893, but as a matter of fact I spent the two preceding years in investigations, employing forms of apparatus, some of which were almost like those of today. . . ."
After a while he began to favor another technique that he called the âdisturbed charge of ground and air method.â Tesla's wireless system used the same basic apparatus, however instead of using electromagnetic space waves, he claimed that the energy was carried by electrical currents through the earth and along with accompanying surface waves. In one form of the system he claimed that the âreturnâ path closing the circuit is an electrical current flow established between two elevated terminals, one belonging to the transmitter and the other the receiver. These consist of currents flowing through ionized air. Once again in Tesla's own words,
"... It was clear to me from the very start that the successful consummation could only be brought about by a number of radical improvements. Suitable high frequency generators and electrical oscillators had first to be produced. The energy of these had to be transformed in effective transmitters and collected at a distance in proper receivers. Such a system would be manifestly circumscribed in its usefulness if all extraneous interference were not prevented and exclusiveness secured. In time, however, I recognized that devices of this kind, to be most effective and efficient, should be designed with due regard to the physical properties of this planet and the electrical conditions obtaining on the same ..."
Nikola Tesla was issued the following relevant patents:
* US patent 645576,
"System of Transmission of Electrical Energy" (March 20, 1900; filed Sept. 2, 1897). In US645576, Tesla cited the well-known radiant energy phenomena and corrected previous errors in theory of behavior. Within this specification, Tesla declared, "The apparatus which I have shown will obviously have many other valuable uses â as, for instance, when it is desired to transmit intelligible messages to great distances [...]".
* US patent 649621, "Apparatus for Transmission of Electrical Energy" (May 15, 1900; filed February 19, 1900). In US649621, Tesla established a system which was composed of a transmitting coil (or conductor) arranged and excited to cause oscillations (or currents) to propagate via conduction through the natural medium from one point to another remote point therefrom and a receiver coil, or conductor, of the transmitted signals.
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 â 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 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.
Guglielmo Marconi: Italian electrical engineer and Nobel laureate known for the development of a practical wireless telegraphy system.
Guglielmo Marconi, who has been called the ''father of radio'', is said to have read about the experiments that Hertz did in the 1880s while he was on vacation in 1894 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 Hertzâs 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 Hertzâs 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 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.
In 1901, Marconi claimed to have received daytime transatlantic radio frequency signals at a wavelength of 366 metres (820 kHz).
[Henry M. Bradford, "''[http://www.antiquewireless.org/otb/marconi1901.htm Did Marconi Receive Transatlantic Radio Signals in 1901]? - Part 1''". Wolfville, N.S..] [Henry M. Bradford, "''[http://www.antiquewireless.org/otb/marconi1901a.htm Did Marconi Receive Transatlantic Radio Signals in 1901]? Part 2, Conclusion: The Trans-Atlantic Experiments''". Wolfville, N.S..] 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. [John S. Belrose, "''[http://www.ieee.ca/millennium/radio/radio_differences.html Fessenden and Marconi; Their Differing Technologies and Transatlantic Experiments During the First Decade of this Century''"] International Conference on 100 Years of Radio, 5â7 September 1995. Retrieved 2008-08-09.] 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 contribution 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 was granted on June 4, 1901. Marconi's was awarded on June 11, 1901, also. This system was more advanced than his previous works.
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.
Summary of "inventors of radio"
The key invention for the beginning of "wireless transmission of data using the entire frequency spectrum" has been attributed to various inventors and researchers. Below is a selection of pertinent events and individuals, from 1860 to 1910, related to the invention of radio.
ImageSize = width:777 height:375
DateFormat = YYYY
Period = from:1860 till:1910
PlotArea = width:716 height:333 left:40 bottom:20
TimeAxis = orientation:vertical order:reverse
ScaleMajor = unit:year increment:10 start:1860
ScaleMinor = unit:year increment:1 start:1860
at:1864 fontsize:S text:"James Clerk Maxwell predicts electromagnetic (EM) waves using a transmission medium.
at:1872 fontsize:S text:"Mahlon Loomis and W. H. Ward (USA) file for U.S. Patents for a "wireless telegraph"."
at:1878 fontsize:S text:"David Edward Hughes transcieves via induction transmission."
at:1885 fontsize:S text:"T. A. Edison uses a vibrator magnet for induction transmission. "
at:1887 fontsize:S text:"Heinrich Hertz publishes his research in the journal Annalen der Physik."
at:1891 fontsize:S text:"Nikola Tesla is granted U.S. Patents No. 447,920, and 447,921 (VLF generators) and 454,622 (RF power supply). Edison receives U. S. Patent No. 465971.
at:1893 fontsize:S text:"Tesla demonstrates wireless techniques at the Franklin Institute in Philadelphia."
at:1895 text:"Alexander Popov presents his radio receiver to the Russian Physical and Chemical Society."
at:1897 fontsize:S text:"Guglielmo Marconi is granted British patent No. 12,039 (Radio patent). Tesla is granted U.S. Patents No. 645,576 and 649,621 (Four-tuned circuit patents)."
at:1900 fontsize:S shift:(0,5) text:"Reginald Fessenden makes the first audio radio transmission."
at:1901 fontsize:S text:"Marconi receives British patent No. 7,777 and reports transatlantic transmission."
at:1904 fontsize:S text:"John Ambrose Fleming develops the "oscillation valve" (vacuum-tube diode). "
at:1906 fontsize:S shift:(0,4) text:"Lee De Forest invents the Audion, now known as the vacuum-tube triode. "
at:1909 fontsize:S text:"Karl Ferdinand Braun and Marconi receive Nobel Prize in physics, 'in recognition of their contributions to the development of wireless telegraphy'."
Tesla vs. Marconi
;United States patent dispute
Radio patent decision
In 1943 a lawsuit regarding Marconi's US radio patents was resolved by the United States Supreme Court, who overturned most of these. The Marconi Company brought this suit in the Court of Claims to recover damages for infringement of four United States patents. Two, and , were issued to Marconi, a third, , to Lodge, and a fourth, , to Fleming. The court held that the Marconi reissue patent was not infringed. In its consideration of radio communication systems, the United States courts accepted a "definition evolved out of the exhaustive depositions taken from many technical experts..."
as requiring "two tuned circuits each at the transmitter and receiver, all four tuned to the same frequency."
The court found Marconi showed no invention over Stone () by making the tuning of his antenna circuit adjustable, or by using Lodge's variable inductance for that purpose. The court decision was based on the proven prior work conducted by others, such as by Nikola Tesla, Oliver Lodge, and John Stone Stone, from which some of Marconi patents stemmed. At the time, the United States Army was involved in a patent infringement lawsuit with Marconi's company regarding radio, leading various observers to posit that the government nullified Marconi's other patents in order to moot any claims for compensation (as, it is speculated, the government's initial reversal to grant Marconi the patent right in order to nullify any claims Tesla had for compensation).
The U. S. Supreme Court stated that,
: "''The Tesla patent No. 645,576, applied for September 2, 1897 and allowed March 20, 1900, disclosed a four-circuit system, having two circuits each at transmitter and receiver, and recommended that all four circuits be tuned to the same frequency. ''[... He]'' recognized that his apparatus could, without change, be used for wireless communication, which is dependent upon the transmission of electrical energy.''"
In making their decision, the court noted,
: "''Marconi's reputation as the man who first achieved successful radio transmission rests on his original patent, which became reissue No. 11,913, and which is not here [320 U.S. 1, 38] in question. That reputation, however well-deserved, does not entitle him to a patent for every later improvement which he claims in the radio field. Patent cases, like others, must be decided not by weighing the reputations of the litigations, but by careful study of the merits of their respective contentions and proofs''."
[''Wireless Telegraph co. of America v. United States''.] The court, therefore, did not consider the issue of whether Marconi was the inventor of radio, since his original patent was not at issue nor, as they stated, being disputed in this particular proceeding. This is because Marconi's original patent was filed with the British Patent Office on June 2, 1896 and therefore pre-dated Tesla's Patent No. 645,576, applied for September 2, 1897 by more than one year.
The court also stated that,
: "''It is well established that as between two inventors priority of invention will be awarded to the one who by satisfying proof can show that he first conceived of the invention''."