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Invention Of Radio
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- This article covers the main arguments about who had what part in the early development of radio.
- "Great Radio Controversy" redirects here. For the album by the band Tesla, see The Great Radio Controversy
- For the general history of radio, see History of radio.
Within the timeline 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.
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- This article covers the main arguments about who had what part in the early development of radio.
- "Great Radio Controversy" redirects here. For the album by the band Tesla, see The Great Radio Controversy
- For the general history of radio, see History of radio.
Within the timeline of radio, several people were involved in the invention of radio and there were many key inventions in what became the modern systems of wireless. Radio development began as "wireless telegraphy". Closely related, radio was developed along with two other key inventions, the telegraph and the telephone. During the early development of wireless technology and long after its wide use, disputes persisted as to who could claim credit for the invention of radio. The matter was important for economic, political and nationalistic reasons.
Physics of wireless signalling
Several different electrical, magnetic, or electromagnetic physical phenomena can be used to transmit signals over a distance without intervening wires. The various methods for wireless signal transmissions include:
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 developed the theory of electromagnetism that predicted the existence of electromagnetic waves. He did not transmit or receive radio waves.
Innovations and laboratory experiments
Hughes
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 Morse code using a transmitter controlled by clockwork.
Hertz
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 Maxwell’s electromagnetic theory. He demonstrated that radio radiation had all the properties of waves (now called electromagnetic radiation), and discovered that the electromagnetic equations could be reformulated into a partial differential equation called the wave equation.
Hertz’s setup for a source and detector of radio waves (then called Hertzian waves or Hertz 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 - we just have these mysterious electromagnetic waves that we cannot see with the naked eye. But they are there."
Asked about the ramifications of his discoveries, Hertz replied, "Nothing, I guess." Hertz also stated, "I do not think that the wireless waves I have discovered will have any practical application." Hertz died in 1894, so the art of radio was left to others to implement into a practical form.
Tesla
Around July 1891, Nikola Tesla constructed various apparatus that produced between 15,000 to 18,000 cycles per second. Transmission and radiation of radio frequency energy was a feature exhibited in the experiments by Tesla which he proposed might be used for the telecommunication of information.
After 1892, Tesla delivered a widely reported presentation before the Institution of Electrical Engineers of London in which he suggested that messages could be transmitted without wires. Later, a variety of Tesla's radio frequency systems were demonstrated during another widely known lecture, presented to meetings of the National Electric Light Association in St. Louis, Missouri and the Franklin Institute in Philadelphia. 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". However, "he almost perversely rejected the notion of transmission by Hertzian waves, which he considered to be wasteful of energy."
Bose
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 a "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.
Edison
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
Tesla
The electromechanical engineer Nikola Tesla, who has been called the father of wireless telegraphy, 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 — the Tesla coil — 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 a 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. 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.
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 “disturbed charge of ground and air method.” Tesla's wireless system used the same basic apparatus, however instead of using electromagnetic space waves, he claimed that the energy was carried by the resonation of electrical currents through the earth and along with accompanying surface waves. In one form of the system he claimed that the ‘return’ 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:
Popov
Beginning in the early 1890s, Alexander Stepanovich Popov conducted experiments along the lines of Hertz's research. In 1894 he built his first radio receiver, which contained a coherer. Further refined as a lightning detector, he presented it to the Russian Physical and Chemical Society on May 7, 1895 — the day has been celebrated in the Russian Federation as "Radio Day". The paper on his findings was published the same year (December 15 1895). Popov had recorded, at the end of 1895, that he was hoping for distant signaling with radio waves.
In 1900 a radio station was established under Popov's instructions on Hogland island (Suursaari) to provide two-way communication by wireless telegraphy between the Russian naval base and the crew of the battleship General-Admiral Apraksin. By February 5 messages were being received reliably. The wireless messages were relayed to Hogland Island by a station some 25 miles away at Kymi (nowadays Kotka) on the Finnish coast.
Marconi
Early years
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 Hertz’s laboratory apparatus into a system designed for communications purposes. At first Marconi used a transmitter to ring a bell in a receiver in his attic laboratory. He then moved his experiments out-of-doors on the family estate near Bologna, Italy, to communicate further. He replaced Hertz’s vertical dipole with a vertical wire topped by a metal sheet, with an opposing terminal connected to the ground. On the receiver side, Marconi replaced the spark gap with a metal powder coherer, a detector developed by Edouard Branly and other experimenters. Marconi transmitted radio signals for about a mile at the end of 1895.
By 1895, 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. Marconi’s late-1895 transmission of signals was for around a mile.
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.
Transatlantic transmissions
In 1901, Marconi claimed to have received daytime transatlantic radio frequency signals at a wavelength of 366 metres (820 kHz). This Poldhu to Newfoundland transmission claim has been criticized. Critics have claimed that it is more likely that Marconi received stray atmospheric noise from atmospheric electricity in this experiment. The transmitting station in Poldhu, Cornwall used a spark-gap transmitter that could produce a signal just below the medium frequency and with high power levels. The message received was the morse letter 'S' - three dots. Dr Jack Belrose has recently contested this, however, based on theoretical work as well as a reenactment of the experiment; he believes that Marconi heard only random atmospheric noise and mistook it for the signal. There are various science historians who agree with Jack Belrose that the Atlantic was not bridged in 1901, but other science historians have taken the position that this was the first trans-Atlantic radio transmission.
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 near 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.
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.
Summary of "inventors of radio"
| Name | Pro | Con | Earliest transmission |
|---|
| Bose | Researched coherers.
Transmitted microwaves over distance of 75 feet in 1895.
Had transmitted microwaves nearly a mile by 1896. | Did not pursue commercialization. | 1895 | | Deforest | Developed the triode amplifier and the Audion tube. | Late upon beginning research into space telegraphy. | 1896 | | Henry | Henry detected electromagnetic effects at a distance of two hundred feet. | He was focused on wired telegraphy and researched self-inductance. | 1829 | | Hertz | By 1888, Hertz had studied and understood the work of Maxwell and, by design, produced the first clear and undisputed experimental evidence for the transmission and reception of radio waves. | Hertz took this work no further, did not exploit it commercially, and famously did not consider it useful. | 1888 | | Hughes | In 1879, Hughes began research into radio waves. He noticed electrical interference in an induction balance he was working with. The observed effect was due to radio waves and he discovered and improved the coherer. | Hughes was not trying to design equipment for wireless communication. His discovery was taken no further. | 1879 | | Lodge | On 14 August 1894 Lodge sent a radio message in Morse code. | Did not pursue further. | 1894 | | Loomis | In 1872, received a patent for a "wireless telegraph". Patent utilizes atmospheric electricity to eliminate the overhead wire used by the existing telegraph systems. | His patent was for the purpose of receiving and imparting atmospheric electricity. | None (n/a) | | Marconi | In summer 1895, Marconi sent signals 1.5 km.
In 1896, applied for British patent protection for a radio system. In 1900, he was granted .
Transmission over 6 km in March and May 1897.
Transatlantic transmission on 12 December 1901.
Tansmission over 3,378 km in February 1902.
Transatlantic message on 17 December 1902.
In 1897 Marconi founded "Wireless Telegraph and Signal Company" and exploited the "Marconi System" of radio commercially.
He shared the 1909 Nobel Prize in Physics with Karl Ferdinand Braun, "in recognition of their contributions to the development of wireless telegraphy". | His 1901 transatlantic transmission is disputed.
Many of Marconi's system components were developed by others. Oliver Lodge claimed British patent of 1900 to contain his own ideas which he failed to patent. | 1895 | | Maxwell | By 1864 Maxwell had become the first person to demonstrate theoretically the existence of radio (electromagnetic) waves, which are used by all radio equipment. | Maxwell did not generate or receive radio waves. | None (n/a) | | Popov | Confirmed laboratory demonstration of radio on 17 May 1895. In March 1896 publicly demonstrated the sending of a signal 550 m between two campus buildings. By 1900 he had reliable communications over 25 miles. | Was not the first to send signals significant distances. | 1895 | | Tesla |
Tesla developed means to reliably produce radio frequency currents.
In 1891 and afterwards, lectured about high-frequency devices and demonstrated devices using power without the use of wires.
Referring to a demonstration of his wireless equipment in 1893 the IEE said "the apparatus that he employed contained all the elements of spark and continuous wave that were incorporated into radio transmitters before the advent of the vacuum tube".
By 1895, stated that he had the ability to transmit signals under 50 miles.
In 1897, Tesla applied for protection for the radio arts. In 1900 Tesla was granted and .
In 1898, demonstrated a radio controlled boat in Madison Square Garden that allowed secure communication between transmitter and receiver.
After 1915, assisted the Telefunken engineers in constructing the Telefunken Wireless Station (the "Arco-Slaby system") in Sayville, Long Island. |
No independently confirmed radio transmissions before 1898.
Primarily because of financial difficulties, Tesla never completed his "worldwide wireless system". The Wardenclyffe Tower transceiver that he began at Shoreham on Long Island, New York was eventually torn down. | 1891 | | Ward | Ward was the first person to be granted a US patent relating to wireless telegraphy. | His patent was for the purpose of receiving and imparting natural electricity. | None (n/a) |
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."
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."
Additional reading
Offline
- Anderson, L.I., "Priority in the Invention of Radio: Tesla vs. Marconi", Antique Wireless Association Monograph No. 4, March, 1980.
- Anderson, L.I., "John Stone Stone on Nikola Tesla's Priority in Radio and Continuous-Wave Radiofrequency Apparatus", The A.W.A. (Antique Wireless Association) Review, Vol. 1, 1986, pp. 18-41.
Weblinks
- ", 320 U.S. 1 (U.S. 1943)", 320 U.S. 1, 63 S. Ct. 1393, 87 L. Ed. 1731 Argued April 9,12, 1943. Decided June 21, 1943.
- Howeth, Captain H.S. , published 1963, GPO, 657 pages. Free online public domain US government published book.
- Wunsch, A.D., ",” Antenna, Volume 11 No. 1, November 1998, Society for the History of Technology
- Brand, W.E., "", Antenna, Volume 11 No. 2, May 1998, Society for the History of Technology
- "", . (1922). London: Encyclopaedia Britannica.
- Mazzotto, D., & Bottone, S. R. (1906). . London: Whittaker & Co.
- Fleming, J. A. (1908). . London: New York and Co.
- Murray, J. E. (1907). . New York: D. Van Nostrand Co.; [etc.].
- Twining, H. L. V., & Dubilier, W. (1909). . Los Angeles, Cal: The author.
- Massie, W. W., & Underhill, C. R. (1911). . New York: D. Van Nostrand.
- Sewall, C. H. (1904). . New York: D. Van Nostrand.
- Collins, A. F. (1905). . New York: McGraw Pub.
- Fahie, J. J. (1900). . Edinburgh: W. Blackwood and Sons.
- Colby, F. M., Williams, T., & Wade, H. T. (1930). "", . New York: Dodd, Mead and Co.
- Trevert, E. (1904). . Lynn, Mass: Bubier Pub.
- Stanley, R. (1919). . London: Longmans, Green.
- Thompson, S. P. (1915). . New York: Macmillan
- . The Electrical engineer. (1884). London: Biggs & Co.
- Simmons, H. H. (1908). "", . London: Cassell and Co.
- Bottone, S. R. (1910). . London: Whittaker & Co.
- Erskine-Murray, J. (1909). . New York: Van Nostrand.
- American Institute of Electrical Engineers. (1884). "", . New York: American Institute of Electrical Engineers.
- by Lucien Poincare, eBook #15207, released February 28, 2005.
- Katz, Randy H., "". History of Communications Infrastructures.
- Waser, André, "", 2000
- American Institute of Electrical Engineers. (1884). . New York: American Institute of Electrical Engineers. (ed., Contains Radio Telephony — By E. B. Craft and E. H. Colpitts (Illustrated). )
- Stanley, R. (1914). . London: Longmans, Green.
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- Ashley, C. G., & Hayward, C. B. (1912). : an understandable presentation of the science of wireless transmission of intelligence. Chicago: American School of Correspondence.
See also
People: Edwin Howard Armstrong, John Stone Stone, Ernst Alexanderson, Reginald Fessenden, Oliver Lodge,Archie Frederick Collins
Radio: Radio communication system, Timeline of radio, Oldest radio station, Birth of public radio broadcasting, Crystal radio
Categories: Radio People, Radio Pioneers, Discovery and invention controversies
Other: List of persons considered father or mother of a field, Radiotelegraph and Spark-Gap Transmitters, The Great Radio Controversy, Induction coil, Ruhmkorff coil, Poldhu, Alexanderson alternator, De Forest tube
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