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Who Invented Radio? See also Coherer Within the timeline of radio (see below), many people were involved in the invention of radio transmission of information as we know it today. Despite this, during its early development and long after wide acceptance, disputes persisted as to who could claim sole credit for this obvious boon to mankind. In the first part of this article is displayed the timeline of radio including history of radio, technology, people and events that produced instruments that use radio waves. In the second part are presented a few controversies dealing with Who Invented Radio?
Origins and developmentsThe identity of the original inventor of radio, at the time called wireless telegraphy, is contentious. The key invention for the beginning of "wireless transmission of data using the entire frequency spectrum", known as the spark-gap transmitter, has been attributed to Nikola Tesla, Guglielmo Marconi, and Alexander Popov. Radio's prehistory (19th century)
Wireless beginningsIn the history of radio and development of "wireless telegraphy", there are multiple claims to the invention of radio. Marconi equipped ships with life saving wireless communications and established the first transatlantic radio service. Tesla developed means to reliably produce radio frequencies, publicly demonstrated the principles of radio, and transmitted long distant signals.
Spark-gap telegraphyUsing various patents, the company called "British Marconi" was established and began communication between coast radio stations and ships at sea. This company along with its subsidiary American Marconi, had a stranglehold on ship to shore communication. It operated much the way American Telephone and Telegraph operated until 1983, owning all of its own equipment and refusing to communicate with non-Marconi equipped ships. Many inventions improved the quality of radio, and amateurs experimented with uses of radio, thus the first seeds of broadcasting were planted. Around the turn of the century, the Slaby-Arco wireless system was developed by Adolf Slaby and Georg von Arco (later incorporated into Telefunken). 
Audio broadcasting (1915 to 1950s)
Westinghouse was brought into the patent allies group, General Electric, American Telephone and Telegraph, and Radio Corporation of America, and became a part owner of RCA. All radios made by GE and Westinghouse were sold under the RCA label 60% GE and 40% Westinghouse. ATT's Western Electric would build radio transmitters. The patent allies attempted to set up a monopoly, but they failed due to successful competition. Much to the dismay of the patent allies, several of the contracts for inventor's patents held clauses protecting "amateurs" and allowing them to use the patents. Whether the competing manufacturers were really amateurs was ignored by these competitors. These features arose:-
Later 20th century developments
Telex on RadioTelegraphy did not go away on radio. Instead, the degree of automation increased. On land-lines in the 1930s, Teletypewriters automated encoding, and were adapted to pulse-code dialing to automate routing, a service called telex. For thirty years, telex was the absolute cheapest form of long-distance communication, because up to 25 telex channels could occupy the same bandwidth as one voice channel. For business and government, it was an advantage that telex directly produced written documents. Telex systems were adapted to short-wave radio by sending tones over single sideband. CCITT R.44 (the most advanced pure-telex standard) incorporated character-level error detection and retransmission as well as automated encoding and routing. For many years, telex-on-radio (TOR) was the only reliable way to reach some third-world countries. TOR remains reliable, though less-expensive forms of e-mail are displacing it. Many national telecom companies historically ran nearly pure telex networks for their governments, and they ran many of these links over short wave radio. 21st century developmentInternet radioInternet radio consists of sending radio-style audio programming over streaming Internet connections: no radio transmitters need be involved at any point in the process. See alsoExternal linksReferencesWho Invented Radio?
Early wireless workScientific theory and verificationJames Clerk Maxwell performed the theoretical physical research that correctly predicted the existence of radio (and all other electromagnetic) waves. Heinrich Rudolf Hertz was the experimental physicist who created radio waves in a controlled laboratory manner. Neither Maxwell nor Hertz, though, devised systems for actual general use or described the application of the technology. Developments, parallel to these individuals and after, are engineering investigations that lead to the 'invention of radio': the objects, processes, or techniques of information transception. Many individuals contributed to the art of wireless, in the air, earth, and water; this includes the precursory work in wireless telephony and wireless telegraphy. SLF and UHF experimentationDavid E. Hughes, eight years before Hertz's experiments and nearly two decades before Guglielmo Marconi's demonstrations, induced electromagnetic waves in a signalling system. Hughes transmitted Morse code by an induction apparatus. In 1878, Hughes's induction transmission method utilized a "clockwork transmitter" to transmit signals. In 1885, T. A. Edison used a vibrator magnet for induction transmission. In 1888, Edison deployed a system of signalling on the Lehigh Valley Railroad. In 1891, Edison attained the wireless patent for this method using inductance (U.S. Patent 465,971). From 1886 to 1888 inclusive in his classic UHF experiments, Heinrich Hertz had proved 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 Hertzian waves), and discovered that the electromagnetic equations could be reformulated into a partial differential equation called the wave equation. Of the three basic forms of wireless aerial launching structures, the Hertz antenna was a center-fed half-wavelength dipole (with the other forms being the Marconi antenna and Tesla antenna). Hertz’s setup for a source and detector of radio waves (archaically called Hertz waves in his honor) comprised a primitive radio system capable of transmitting and receiving space waves through free space.[1] His transmitter was not at all efficient and was severely limited in power output. Its dipole antenna differed from the vertical quarter-wavelength antenna that was subsequently adopted by Marconi and others in that it was not grounded.[2] 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 wave. 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."[3] 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 useful form. His discoveries would later be taken up by entrepreneurs looking to make their fortunes. Marconi's 1895 experiments followed Hertz's work (among others) by using a spark source in what became known as a spark-gap transmitter. Tesla's work
Radio frequency generationNikola Tesla was one of the first to patent a means to reliably produce radio frequency currents. Tesla's U.S. Patent 447,920, "Method of Operating Arc-Lamps" (March 10, 1891), describes an alternator that produced high-frequency current (for that time period), around 10,000 cycles per second. (The term cycles-per-second was later modified to "hertz.") His patentable 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. The alternator produced frequencies in the Very Low Frequency (VLF) band. Continued research and patentsAround July 1891, he established his New York laboratory and constructed various apparatuses that produced between 15,000 to 18,000 cycles per second. At this location, he also lit vacuum tubes wirelessly (thus providing hard evidence for the potential of wireless transmissions). Transmission and radiation of radio frequency energy was a feature exhibited in the experiments by Tesla and was noted early on to be used for the telecommunication of information.[4][5] In 1892, Tesla delivered a widely reported presentation before the Institution of Electrical Engineers of London in which he noted, among other things, that intelligence would 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".[6] In late 1896 or early 1897 Tesla received wireless signals transmitted from the Houston St. lab in New York City to West Point, "a distance of about 30 miles." The transmitter consisted of an RF alternator and produced undamped (or continous) waves in the neighborhood of 5,000 cycles per second. 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.[7][8] In 1899 Tesla established an "Experimental Station" in Colorado Springs where he continued his research into wireless transmission principles often using a form of electrical oscillator known as the magnifying transmitter. 
An early Tesla tramsmitter consisting of a flat-spiral quarterwave resonator and an elevated terminal. This image is from one of Tesla's patents. 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 radiated as a common "Hertz wave" antenna. In Tesla's own words,
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 the energy is carried by the conduction of electrical currents through the earth and along with accompanying surface waves. In one form of the system 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 conduction currents flowing through plasma and also electrostatic induction. Once again in Tesla's own words,
In other words, Tesla’s structure injected a large alternating current into the earth via the ground terminal. Tesla's discovery of importance was the "Surface wave" method. The production of surface waves as described by Arnold Sommerfeld and Jonathan Zenneck was partially the consequence of adding a deep ground connection to the transmitter. Tesla said in 1893 that "One of the terminals of the source would be connected to Earth [as a electric ground connection ...] the other to an insulated body of large surface.[11] A shallow buried ground plane or an elevated insulated counterpoise is commonly used in the construction of low and medium frequency 1/4-wavelength radio antennas. These lend to the development of the Norton Surface Wave. This method led to longer transmission ranges. Many AM stations use this same principle to boost reception of their signals.[12] This also allow modern grounded AM 1/4 wavelength monopole antenna to be more practical in order to overcome the restrictions imposed upon designers by the large physical dimensions required for these structures. Radio antennas radiate electromagnetic waves that can reach the receiver either by ground-wave propagation or by refraction from the ionosphere, known as sky-wave propagation. 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, and under certain conditions a tropospheric ducting component. The direct-wave is limited only by the distance from the transmitter to the horizon plus a small distance added by atmospheric 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.][13] Nikola Tesla's rights to radio were based upon these patents:
Shortly after the turn of the 20th century, the US Patent Office also awarded Marconi a patent for radio. Popov's workBeginning 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 signalling with radio waves.[14] In 1900, Popov stated (in front of the Congress of Russian Electrical Engineers),
Bose's work
In November 1894, the Bengali Indian physicist, Jagdish Chandra Bose, demonstrated publicly the use of radio waves in Calcutta, but he was not interested in patenting his work.[16] For more information see History of radio : Jagdish Chandra Bose. 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." The 1895 public demonstration by Bose in Calcutta was before Marconi's wireless signalling experiment on Salisbury Plain in England in May 1897.[17][18] Though Bose did this demonstration, Tesla had performed radio communication earlier in 1892 and 1893. 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.[19] Later he received U.S. Patent 755,840, "Detector for electrical distrubances" (1904), for a specific electromagnetic receiver. Though he did not file any patents for transmission, he is recognized for contributing to the development of radio. Marconi's workEarly years
Guglielmo Marconi's proponents say that while on vacation in 1894 he read about the experiments that Hertz did in the 1880s, and about Nikola Tesla's work in the just-published book Inventions, Researches and Writings of Nikola Tesla. It was at this time that Marconi began to understand that radio waves could be used for wireless communications.[20] Marconi's early apparatus was a development of Hertz’s laboratory apparatus into a system designed for communications purposes. At first he 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.[21] 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. Marconi and his company were not alone in the field; his principal competition came from German scientists whose work would become the basis for the Telefunken company (which Nikola Tesla assisted in building). Marconi's U.S. Patent 586,193 (July 13, 1897) (and the reissued U.S. Patent RE11,913) disclosed a two-circuit system for the transmission and reception of "Hertzian waves" (though he would later acknowledge that in the early wireless systems the "waves do not propagate in the same manner as free radiation from a classical Hertzian oscillator, but glide along the surface of the Earth"[22]). The transmitter was an antenna circuit, with an aerial plate and a ground plate, and a spark gap. Induced signals in the circuit were caused to discharge through a spark gap, producing oscillations which were radiated. The receiver contained an antenna circuit, an aerial plate and a ground plate, and a coherer. Marconi's apparatus was to be resonant (commonly called by various researcheres at the time syntonic). This was done by the careful determination of the size of the aerial plates. The Poldhu experimentIn 1901, Marconi claimed to have received daytime transatlantic radio frequency signals at a wavelength of 366 metres (820 kHz).[23][24][25] The early spark transmitters may have been broadly tuned and the Poldhu transmitter may have radiated sufficient energy in that part of the spectrum for a transatlantic transmission, if Marconi was using an untuned receiver when he claimed to have received the transatlantic signal at Newfoundland in 1901. When he used a tuned receiver aboard the SS Philadelphia in 1902, he could only receive a daytime signal from Poldhu, a distance of 700 miles, less than half the distance from Poldhu to Newfoundland. At night the signals were reported to have been received several times further, and his successful transatlantic transmissions from Glace Bay, Nova Scotia in 1902 were made at night. Marconi would later found the Marconi Company and would jointly receive the 1909 Nobel Prize in Physics with Karl Ferdinand Braun. Marconi’s 1901 Poldhu to Newfoundland transmission claim has been attacked.[26] Critics have claimed that it is more likely that Marconi received stray atmospheric noise from atmospheric electricity in the 1901 experiment.[27] 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 (a maximum time-averaged power of 35 kilowatts, but with a peak pulse power of megawatts). 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 (in addition to being bolstered by Tesla supporters) 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. Court decisionIn 1943 a lawsuit regarding Marconi's numerous other radio patents was resolved by the U.S. Supreme Court, who overturned most of these. 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 court decision was based on the proven prior work conducted by others, such as by Tesla, Oliver Lodge, and John Stone Stone, from which some of Marconi patents (such as U.S. Patent 763,772) stemmed. The U. S. Supreme Court stated that,
In making their decision, the court noted,
The court also stated that,
Case of priority Case for MarconiMarconi supporters have stated that Marconi was not aware of the works of Nikola Tesla in the United States. It is unlikely, though, that Marconi was unaware of Tesla's presentations. Both On Light and Other High Frequency Phenomena (Philadelphia/St. Louis; Franklin Institute in 1893) and Experiments with Alternating Currents of High Potential and High Frequency (London; 1892) were reported on internationally. Tesla's 1893 presentation at the Franklin Institute was reported across America (such as in The Century Magazine) and throughout Europe.[31] Tesla also performed public demonstrations of actual and related work, such as the remote-controlled boat in 1898 (which was protected under U.S. Patent 613,809). The remote-controlled boat contained "rotating coherers" that allowed secure communication between transmitter and receiver. Case against MarconiBy 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.[32] Marconi's later practical four-tuned system was pre-dated by N. Tesla, Oliver Lodge, and J. S. Stone. Tesla was the first, though, to expound the principles of the four-tuned system. The earlier two-tuned systems were not practical for commercial activity (as found in the United States court case). In addition, other prior work was conducted by others (such as by Hertz and Bruan, but not excluding others) from which many of Marconi's devices and methods were derived. Marconi's U.S. Patent 676,332 Apparatus for wireless telegraphy [1901], in which a more intricate system was disclosed than in his earlier patents, was filed after contributions made by other investigators. Marconi’s late-1895 transmission of signals was for around a mile. This was small when put against Tesla's early-1895 transmissions of up to 50 miles. Case for TeslaNikola Tesla was first to hold the rights to radio:
Tesla's system can produce a variety of wave propagations, pending the driving apparatus. Tesla believed that his wireless system would be better than most other radio systems because transverse electromagnetic waves (whose behavior depends on their wavelength) would decay as they travelled from the transmitter, making the signals uselessly weak at long distances. Tesla advanced that longitudinal electromagnetic waves (such as those that occur in waves in plasmas) through the medium would be used, as he theorized that they would be practically lossless. His devices can be driven to produce either transverse or longitudinal waves. There is also the relevance of Tesla demonstrations of the remote-controlled boat (with its internal rotating coherer) as well as Tesla's public lecture demonstrations. Besides his intention to transmit wireless signals of intelligence, he proposed to transmit electric power via electrical conduction through the earth and the upper atmosphere, as well as in between them both (in the earth-ionosphere region which is now known as a resonant cavity). This power transmission was to be done not by "hertzian waves," but through standing surface waves. Tesla’s proposed wireless transmitter utilized a resonant transformer to apply a very high voltage of high frequency between the earth and a large elevated conductor, as discussed earlier. Case against TeslaTesla never completed his "worldwide wireless system," primarily because of financial difficulties. Cost overruns stopped him from completing the Wardenclyffe Tower (a "wireless station tower") that he built in the early 1900s in Shoreham on Long Island, New York. See alsoNotes
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