Fullscreen HTML5Med Res (??MB)HTML4

Feature Article 1856–1943 Nikola Tesla the original ‘mad scientist’ B efitting someone who made such contributions, he was said to have been born during a violent lightning storm at midnight between July 9th and 10th, 1856, in Croatia. According to his family, the midwife said the lightning was a “bad omen” and that he would be a “child of darkness”, to which the mother replied, “No. He will be a child of light.” Fortunately, he became a force for good and lived for 87 years. He passed away in 1943, leaving a remarkable and world-changing legacy, which we will now examine. Of his numerous inventions & developments, among the most important were his contributions to three-phase AC electricity, the induction motor, the Tesla coil (used in many early radios) and one of the world’s first hydroelectric power plants. The development of three-phase electricity allowed the transmission of electrical power over long distances, one basis of modern industrial civilisation. The electric car company Tesla is named after him. Two museums are dedicated to him, and there are statues of him on Goat Island, USA and Queen Victoria Park, Canada, both near Niagara Falls. There are also several Tesla memorial plaques in Manhattan, New York, USA. Tesla’s thought processes Tesla on the cover of Electrical Inventor magazine, February 1919. The lead image is based on a photo of Tesla from around 1900 demonstrating wireless power transmission. He is holding a partially evacuated glass bulb that’s glowing due to the electric field from a nearby Tesla coil. See https://w.wiki/ AZMz Tesla’s creative genius might be attributable to his unusual thought processes. These facilitated his ability to visualise and create things. He wrote in Electrical Experimenter, February 1919: In my boyhood I suffered from a peculiar affliction due to the appearance of images, often accompanied by strong flashes of light, which marred the sight of real objects and interfered with my thought and action. They were pictures of things and scenes which I had really seen, never of those I imagined... I was quite unable to distinguish whether what I saw was tangible or not. Then I observed to my delight that I could visualize with the greatest facility. I needed no models, drawings or experiments. I could picture them all as real in my mind. Thus I have been led unconsciously to evolve what I consider a new method of materializing inventive concepts and ideas, which is radically opposite to the purely experimental and... so much more expeditious and efficient. 68 Practical Electronics | October | 2025 Nikola Tesla was a prolific inventor, engineer, futurist and essayist. He spoke eight languages, had a wide range of interests and has been described as a “Renaissance man”. Despite his ‘mad scientist’ vibe, his contributions to our modern industrial civilisation are significant. Part 1 by Dr David Maddison, VK3DSM The Life of Nikola Tesla, part one ... My method is different. I do not rush into actual work. When I get an idea I start at once building it up in my imagination. I change the construction, make improvements and operate the device in my mind. It is absolutely immaterial to me whether I run my turbine in thought or test it in my shop. I even note if it is out of balance. There is no difference whatever, the results are the same. In this way I am able to rapidly develop and perfect a conception without touching anything. When I have gone so far as to embody in the invention every possible improvement I can think of and see no fault anywhere, I put into concrete form this final product of my brain. Invariably my device works as I conceived that it should, and the experiment comes out exactly as I planned it. Also, like many creative geniuses, he had various eccentricities. Tesla, mathematics and quantitative theories Tesla was different from most other scientists and engineers. His writings are highly descriptive and contain few equations. He was a visual thinker and performed mathematics ‘visually’ rather than presenting it through formal methods. He also did not accept Maxwell’s equations, which are the basis of electricity, magnetism and optics. (“We can no longer believe in the Maxwellian hypothesis of transversal ether-undulations and the literal truth of its corollaries.” – https:// pemag.au/link/aby0). He generally ignored quantitative theories; it has been suggested he may have suffered from “mathematical aphasia”. His work was experimental, usually practical, descriptive and not analytical. In that respect, he was much like Michael Faraday; it was Maxwell who turned Faraday’s intuitive ideas into equations. Separating fact from fiction While Tesla’s contributions to technology were undoubtedly outstanding, it should be recognised that work has been attributed to Tesla that either he did not originate or where he was a partial contributor. Also, during his lifetime, there was fierce commercial competition regarding which electrical supply technology was to be adopted, so there were Practical Electronics | October | 2025 An American postage stamp featuring Nikola Tesla. Source: https://postalmuseum.si.edu/ object/npm_2008.2007.74 often claims and counterclaims made that didn’t necessarily reflect the reality of who invented what. Tesla had no marketing department; he had to do his own promotion, which is often reflected in his writing style. Not all of Tesla’s inventions or ideas were successful or viable. Tesla’s early work, such as with the induction motor, generators and the Tesla coil was excellent. However, some of his later work, which involved long-­ distance wireless electricity transmission, was not based on sound physical principles. Tesla’s patents Tesla was prolific and obtained around 112 US patents, 29 UK patents and six Canadian patents. He applied for 33 patents that were not granted. He also had patents in other countries for a total of around 300; for a complete list, see https://w.wiki/AZLY Tesla’s life and career We will now take a look at some of Tesla’s milestones in chronological order. This article will end in 1897; the remainder will be covered in the second and final article in this series, to be published next month. University 1875 to 1878 Tesla studied engineering from September 1875 at the Graz University of Technology in Austria but, having started with excellent results, did not finish his degree. He left after the first semester of the third year, apparently losing interest in his studies while spending too much time in a café and associated activities. He sat no exams that year and was excluded. While at university, he saw a Gramme dynamo, which operated either as a generator or motor. He conceived a way to eliminate the commutator, which his professor didn’t believe was possible. This ultimately led to Tesla’s development of the AC induction motor, which contains no commutators. He received an honorary doctorate from Graz in 1937. Prague 1880 Tesla arrived in Prague and spent much of his time reading at the Klementinum Library and Národní Kavárna Interesting facts about Nikola Tesla ● He had a great sense of humour. ● He was a rival of Edison, not a sworn enemy; they had a mutual respect for each other. ● He had the idea of a ‘smartphone’ type device in 1901. He described to his then-backer J.P. Morgan a handheld device he said would deliver stock quotes and telegram messages. ● For unknown reasons, he hated pearls and would not speak to any lady wearing them. ● He had a photographic memory. ● He had a fear of germs, always wore white gloves and rarely shook hands. ● He asked for large numbers of napkins at meals. ● He never stayed in a room or floor number divisible by three. ● He ran his life according to a strict daily schedule. ● He was very particular about dress and grooming. ● He had a beloved pet pigeon. ● The SI unit for magnetic flux is named after him, the Tesla (T). ● Toward the end of his career, he ran out of profitable ideas, or at least people who were prepared to back him financially. As a result, he passed away in poverty with many unpaid debts. 69 Feature Article café. He also attended lectures at the University of Prague but was not enrolled as a student. magnetic field combined to create the AC induction motor. Budapest Telephone Exchange 1883 1881 In 1881, Tesla commenced work with the Budapest Telephone Exchange, a new company that was not yet functional. So he helped set it up, as a draftsman and later chief electrician, making several design improvements. Continental Edison Company 1882 In 1882, Tesla worked for Edison in Europe. He started by installing lighting systems, but his expertise was noted, and he became involved in designing improved dynamos and motors. Rotating magnetic fields 1882 The idea of a rotating magnetic field was conceived as early as 1824 by François Arago but, according to Tesla, he conceived of its use in an AC electric motor while walking through a park in Budapest in 1882 (documented on p198 of the PDF at https://pemag.au/ link/aby0). Although he doesn’t explicitly mention the rotating magnetic field, it was the basis of the motor. His idea of eliminating commutators and the rotating Prototype induction motor In 1883, while working for Edison in Strasbourg, he constructed (on his own time) an induction motor but could not find any interest in it. Emigration to the USA 1884 Tesla’s manager in Europe was recalled back to Edison in the USA and requested Tesla to come to work at the Edison Machine Works in New York City. There, he managed staff involved in installing New York’s electricity utilities. He was also involved in developing an arc lamp street lighting system, but that needed high voltages and was incompatible with the Edison system. Tesla’s designs were not utilised; there had been improvements in incandescent lighting. Tesla only worked there for six months before he left, apparently after a dispute about an alleged promised bonus. Tesla Electric Light & Manufacturing 1885 After leaving Edison, investors asked Tesla to design a system of electric arc lamps for lighting the streets of New York and other cities. This led to the establishment of the Tesla Electric Light and Manufacturing Company. What is polyphase electricity? Many early writings on AC electricity use the term “polyphase”. Polyphase refers to an AC electrical system with two or more AC voltage supplies supplied by separate wires and with the sinewaves of each displaced from each other by a certain amount, usually described in degrees. Early work on polyphase systems was with two phases, but today, three phases is the most common configuration. A three-phase system is twice as efficient at conductor utilisation as a single-phase system. Polyphase power, especially three-phase, is ideal for induction motors, as it can easily generate a rotating magnetic field, eliminating high-maintenance commutators and allowing simple and inexpensive construction. The principle of a rotating magnetic field in a threephase induction motor. The magnetic field sequentially rotates between the various motor poles, causing the rotor to follow it and rotate. 70 Tesla continued obtaining patents for motors, generators and other equipment, but the investors showed no interest in those. They decided manufacturing was too competitive and just wanted to run an electric utility. They left the company, which left Tesla penniless; worse, he had assigned his patents to them in return for the now-worthless stock. He described it as “the hardest blow” he ever received. Digging ditches 1886 to 1887 After the failure of his company, he made a living digging ditches. Labs in New York 1887 to 1902 During this period, Tesla maintained a series of laboratories in Manhattan, New York. They were on Liberty Street (1887-1889), Grand Street (1889-92), South Fifth Avenue (1892-95) and East Houston Street(1895-1902). The Tesla Electric Company 1887 In 1887, with new investors, Tesla set up the Tesla Electric Company and the Liberty Street laboratory. In the same year, he invented an induction motor (patented in 1888) that would run on the newly developed AC system. It was becoming popular in Europe because of its advantages of long-distance transmission with little electrical loss. The motor used polyphase current which, at the time, was two-phase (we have three now). The polyphase current generated a rotating magnetic field. The advantage of this motor was that it did not need a commutator, which caused sparks, required high maintenance, and was expensive and complex. Apart from motors, Tesla developed generators and other power system devices. Polyphase induction motor patent 1888 In 1888, Tesla obtained US patent 381,968, the first of a series on electric motors (it continued until 1896). It was for commutator-free polyphase alternating current induction motors (see Fig.1). He envisaged two- and threephase motors in that patent. He also published descriptions of other motors, including a synchronous motor for which the rotation speed is locked to the AC power frequency. Those are ideal for clocks and other motors where precise speed control is essential. Practical Electronics | October | 2025 The Life of Nikola Tesla, part one induction and other types of electric motors and generators. Independently wealthy 1889 Tesla became independently wealthy due to Westinghouse licensing his patents, so he had the funds from 1889 to pursue his own interests. It has been suggested that Tesla was not a particularly good businessman and was always looking for investors, unlike Edison. Also, Tesla tended to work for himself, while Edison employed many other people and had multiple projects on the go at once. Wireless lighting 1890 Fig.1: a model of Tesla’s first induction motor at the Tesla Museum, Belgrade, Serbia. Source: https://w.wiki/AZM$ Galileo Ferraris independently invented and demonstrated a commutator-free two-phase alternating current induction motor in 1885, but he didn’t patent it because he could see no practical application. alty clause on the motors and he later purchased the patent. The cancellation of the royalty clause meant that Tesla would get a minute amount of the true value of his motor and generator patents. Westinghouse Polyphase current and generators George Westinghouse of the Westinghouse Electric & Manufacturing Company was already marketing an AC power system and needed a suitable AC motor. He considered using Ferraris’ motor but decided that Tesla’s was superior. Tesla’s investors negotiated with Westinghouse in 1888 to license his AC transformer, dynamo and motor designs for cash and stock plus a royalty per horsepower of AC motor sold. He also hired Tesla as a consultant for a hefty fee. During 1888, there was intense competition between the three main electrical companies: Westinghouse, Edison and the Thomson-Houston Electric Company. There was also the emerging “war of the currents” between the AC system promoted by Westinghouse and the DC system promoted by Edison. Tesla’s motor was not immediately successful, and the adoption of the polyphase AC system was limited. The intense competition meant that Westinghouse did not have the resources to continue to develop Tesla’s induction motor or the polyphase AC system. Westinghouse was then in serious financial trouble. He explained the difficulties to Tesla, and in 1891, Tesla released Westinghouse from the roy- The first of two important patents this year was US patent 390,413 for a “System of Electrical Distribution” for electrical transmission of polyphase power such that “two or more circuits may have a single return path or wire in common”. The second was US patent 390,414 on a “Dynamo Electric machine” concerning adapting existing dynamos easily and cheaply to polyphase alternating current. 1888 Practical Electronics | October | 2025 1888 A large number of patents 1888 to 1891 This period was enormously productive for Tesla; many patents were granted, including 43 US patents in the area of single and polyphase currents, In 1890, Tesla started experimenting with wireless lighting and performed public demonstrations with power transmitted by inductive or capacitive coupling. This work continued for about another ten years. Tesla coil 1891 In 1891, Tesla patented a type of resonant transformer that is now known as the Tesla coil (US patent 454,622). A resonant transformer uses capacitors across one or more windings, which act as coupled resonant tuned circuits. It produces high-voltage, low-current, pulsed or AC electricity at radio frequencies. Voltages produced can range from 50kV to millions of volts at 50kHz to 1MHz. The essential elements of a Tesla coil are an air-cored ‘oscillation transformer’, a capacitor, a high voltage primary transformer and a spark gap. Tesla used these coils in numerous experiments and built them to very large sizes, such as in Colorado and Wardenclyffe. Experiments Tesla used the coils for included investigating biological effects, high-frequency phenomena, lighting (for which the Fig.2: Tesla giving a demonstration of wireless power transmission in 1891. Source: https://w.wiki/ AZN2 71 Feature Article original patent was issued), phosphorescence, radio, wireless power transmission and X-rays. Tesla made a radio antenna out of the high-voltage end of the secondary part of the transformer, turning it into a radio transmitter. Such an arrangement was used in most early spark-gap radios for wireless telegraphy applications until the 1920s, when the vacuum tube rendered them obsolete. Lighting power supply 1891 In 1891, he applied for and was granted US Patent 454,622 for a means of generating high-voltage and highfrequency electricity for lighting purposes. Incandescents & power transmission 1891 In this year, he obtained US Patent 455,069 for an incandescent light. On May 20th, Tesla demonstrated wireless power transmission to the American Institute of Engineers in a lecture hall at Columbia University. The lecture was entitled “Experiments with alternate currents of very high frequency and their application to methods of artificial illumination”. In one demonstration, he vertically suspended two large zinc sheets from the ceiling, which were connected to a high-frequency, high-voltage Tesla coil. He held an unconnected gas-filled tube between them, and the tube glowed due to the electrostatic field between the sheets, just as a fluorescent tube glows when near a high-­voltage power line due to capacitive coupling. Wireless power transmission 1891 to 1898 Tesla’s dream was global wireless electrical transmission. From 1891 to 1898, he performed numerous experiments and demonstrations in wireless Fig.4: in Tesla’s design, two single-phase alternators were magnetically coupled, 90° out-of-phase to provide two-phase AC for the exposition lighting. Note the alternator’s size in relation to the man. Source: https://historicpittsburgh.org/ islandora/object/pitt:20170320-hpichswp-0011 transmission via capacitive or inductive coupling (see Fig.2). In 1899, he commenced larger-scale experiments at Colorado Springs and later Wardenclyffe. AIEE organisation 1892 to 1894 From 1892 to 1894, he was vice president of the American Institute of Electrical Engineers, a forerunner of the IEEE. Visit to Europe 1892 He gave a series of lectures in London and Paris on “Experiments with alternate currents of high potential and high frequency”. Chicago World’s Fair 1893 Also called the World’s Columbian Exposition, was a significant turning point in the “war of the currents”, with Fig.3: nighttime lighting at the 1893 Chicago World’s Fair using Tesla’s patented AC and lighting systems. Source: https://w.wiki/ AZN3 George Westinghouse winning the lighting contract ($399,000) over Edison’s DC system ($554,000) – see Fig.3. Westinghouse used Tesla’s AC power patents to power lighting of their own design (they could not use Edison’s lights). The lighting and other systems at the fair used twelve 745kW 60Hz single-phase AC generators of Tesla’s design. These were mounted in pairs and arranged to provide two-phase power (see Fig.4). The Westinghouse Company also had a section showcasing Tesla’s inventions, such as induction motors (Fig.5) and generators. The rotating magnetic field used in induction motors was demonstrated with the “Egg of Columbus” (Fig.7). Tesla demonstrated wireless lighting using neon tubes, although he did not invent neon lighting (see Fig.6). He also demonstrated clocks synchronised to the mains frequency. Talks at Franklin Institute & NELA 1893 His talk was “On light and other high frequency phenomena” and he mentioned the “transmission of intelligible signals and power to any distance without the use of wires” (radio). He also discussed the idea of transferring power over long distances through the Earth. Niagara Falls hydroelectric power 1893 In 1893, Tesla was invited to consult for the Niagara Falls hydroelectric 72 Practical Electronics | October | 2025 The Life of Nikola Tesla, part one Fig.5: an exhibition of Tesla’s motors and the “Egg of Columbus” at the 1893 Chicago World’s Fair. Source: https://w.wiki/AZN4 ► Fig.6: Tesla’s wireless lighting demonstration using neon tubes at the Chicago World’s Fair. project. Proposals that had been put forward for the electrical system included two- and three-phase AC and high-voltage DC. Tesla advised that a two-phase AC system from Westinghouse, designed by Tesla and based on his patents, was the best and most reliable option (see Fig.9). Westinghouse was awarded the main contract based on Tesla’s advice and the success of the Tesla and Westinghouse displays and lighting system at the Columbian Exposition. Nine of the twelve patents used for the plant’s machinery were Tesla’s. Electricity from the plant first went to a nearby factory in 1895 and then to Buffalo, New York, in 1896. At a talk about the City of Buffalo receiving power from Niagara on January 12th, 1897, at the Ellicott Club, Tesla said: It is a monument worthy of our scientific age, a true monument of enlightenment and of peace. It signifies the subjugation of natural forces to the service of man, the discontinuance of barbarous methods, the relieving of millions from want and suffering. From “The Age of Electricity” by Nikola Tesla, Cassiers Magazine – London, March 1897, pp378-386. This AC power plant is regarded as the final victory of the “war of the currents”, with Tesla’s AC proving itself superior to Edison’s DC. A low frequency of 25Hz was chosen, as it was expected that much of the Fig.7: a drawing of the “Egg of Columbus” that was designed to demonstrate the rotating magnetic field devised by Tesla. Source: https://w.wiki/AZN5 Practical Electronics | October | 2025 power would be converted to DC via rotary converters for uses such as aluminium production. However, it was realised that three-phase power was superior for transmission efficiency, so phase-changing transformers were used to convert the two-phase power to three-phase. These are known as “Scott-T” transformers since they were invented by Charles F. Scott, who worked for Westinghouse in the late 1890s. The configuration of this type of transformer is shown in Fig.12. The first output phase (0°) is a direct transformer-­coupled copy of the first input phase (0°) via transformer T1. The second phase at 120° is generated by connecting the centre tap of Fig.8: a drawing of Tesla lecturing before the French Physical Society and The International Society of Electricians in the 1880s. 73 Feature Article Fig.9: ten 3.7MW 25Hz 2kV Westinghouse generators at Edward Dean Adams Power Plant in Niagara Falls, installed in 1895. The voltage was stepped up to 10kV or 20kV depending upon how far away the destination was. These generators remained in use until 1961. Source: https://w.wiki/AZN6 Fig.10: the “unipolar vacuum tube” comprising a glass bulb (b), a single electrode (e) and a lead-in conductor (c). A second electrode could be added towards the bottom; otherwise, the return circuit was via capacitive coupling through the air. Source: Tesla Universe – https://pemag.au/link/abyf T1’s secondary to the lower (90°) end of T2’s secondary and adding a tap at √3 ÷ 2 or 86.6% of T2’s secondary. The third phase requires no extra connections to generate as the 240° waveform is simply available as 360° − 120° (360° = 0°), so between the start of T1’s secondary and that same 120° tap. This can also work in reverse, to convert three-phase to two-phase, but in that case the load has to be perfectly balanced, as it would be in a motor. Wireless World System 1893 and later In 1893, he established the foundations of what he would call in a 1900 brochure, “The Wireless World System”. It was to be a global wireless communications and wireless power transmission system (see Fig.13). According to Tesla, it would allow “the transmission of electric energy without wires” as well as point-to-point communications. He said that the communications aspects of the system would allow “the instantaneous and precise wireless transmission of any kind of signals, Fig.12: a simple but clever way to convert twophase AC to threephase. messages or characters, to all parts of the world.” and “... an inexpensive receiver, not bigger than a watch, will enable him [the user] to listen anywhere, on land or sea, to a speech delivered, or music played in some other place, however distant”. In 1915, in the New York Times, he added that the system “would enable thousands of persons to talk at once between wireless stations and make it possible for those talking to see one another by wireless, regardless of the distance separating them” (see page 136 of the PDF at https://pemag.au/ link/aby0). All that sounds very familiar today! To implement this system, he convinced banker John Pierpoint Morgan (J.P. Morgan) to invest in this project, which he built at Wardenclyffe on Long Island, New York (more on that next month). Tesla received numerous patents for wireless communications and power transmission, such as transformer design, transmission methods, tuning circuits and signalling methods. Tesla also envisaged a system of thirty telecommunications towers worldwide, linked to telegraph and telephone systems. He proposed transmitting “radiations”, which were not Hertzian waves and would apparently travel through the Earth with little loss. The energy of such waves could be harnessed anywhere on Earth simply by placing a wire in the ground. We now know that radio waves do not travel through the Earth to any significant degree. A reciprocating engine 1894 In 1894, Tesla received US patent 514,169 for a multipurpose reciprocating engine device that used gas or Hand pump The wireless light: place a wire in the ground that is all G = pressure indicator gages Flexible spherical envelope filled with liquid or gas Analogy of Tesla’s Earth Wave Vibration Theory Each pulse of the pump is felt with equal force at all points of he sphere Tesla’s wireless power for properlling ships and aeroplanes Tesla’s Wireless Transmission Theory The oscillating energy surges thru the Earth to every point on the globe. Thus electric light, heat and power can be drawn to any point of the Earth from a universal central station Fig.13: Tesla’s proposed scheme to deliver light and power anywhere on Earth by “ground waves” travelling through the Earth. Illustration by Tesla from Electrical Experimenter, February 1919. Source: https://w.wiki/AZN8 74 Practical Electronics | October | 2025 The Life of Nikola Tesla, part one Fig.11: a colourised photo of the interior of Tesla’s East Houston St lab. It is lit by lights of Tesla’s design. Source: https://teslaresearch. jimdofree.com/ labs-in-newyork-1889-1902/ steam pressure to generate mechanical oscillatory movement to generate electricity or for other purposes. The development of efficient steam turbines rendered its use for electricity generation obsolete. In the New York World-Telegram of July 11th, 1935, Tesla recounted an incident of 1887 or 1888 where he said a little version of this device apparently brought an entire building to resonance, potentially destroying the building had he not stopped the it with a hammer (www.rexresearch. com/teslamos/tmosc.htm). Mythbusters looked at this in their episode on “Nikola Tesla’s Earthquake Machine!” (season 4, episode 20 – https://youtu.be/LHsHiKtjoag). X-rays 1894 In 1894, Tesla worked with Crookes tubes and a “unipolar vacuum tube” of his own design. He noted mysterious damage to photographic plates in his laboratory by some sort of radiant energy. Although X-rays had yet to be discovered or named, Tesla realised the source of the damage was rays from the point where the “cathodic stream” in the devices struck the anode (Crookes tube) or glass wall (his tube) – see Fig.10. It was later discovered that such a process generates X-rays. In 1895, Wilhelm Röntgen discovered and published work about this “new kind of rays” (X-rays). Tesla started to work on X-rays and, in 1896, he reported being able to produce radiographs at a distance of ~12m; see https://pemag. au/link/aby0 (p33). Practical Electronics | October | 2025 Had Tesla fully recognised the phenomenon causing damage to his photographic plates, he may have been credited with their discovery. Tesla gave Röntgen full credit for his discovery. Later versions of Tesla’s unipolar vacuum tube had a cooling system. Laboratory fire 1895 In March 1895, Tesla’s laboratory at South Fifth Ave, New York (occupied 1892-1895) burned to the ground. Tesla lamented, “I am in too much grief to talk. What can I say? The work of half my lifetime, very nearly all my mechanical instruments and scientific apparatus, that it has taken years to perfect, swept away in a fire that lasted only an hour or two... Everything is gone. I must begin over again.” This is said to have delayed his application for radio patents. Wireless power experiments 1895 In his East Houston Street laboratory (1895-1902), he conducted experiments on the wireless transmission of electricity, setting up large Tesla coils, other types of resonant transformers and other apparatus (see Fig.11). He was producing up to 4MV, the maximum he could safely work with in a city building. The Nikola Tesla Company 1895 In 1895, the Nikola Tesla Company was set up to fund, develop, and market Tesla’s patents, which it did for the next few decades. Transformers/induction coils 1897 In 1897, he was granted US patent 593,138 for a safe high-­voltage, highfrequency electrical transformer/induction coil. In this patent, he showed single-wire electricity transmission with the return circuit flowing through the Earth. This concept was recently demonstrated in 2023, when 5kW was transmitted over 5km with 87% efficiency; see https://ieeexplore.ieee.org/­ document/10023995 Application for radio patents 1897 In 1897, Tesla applied for US patents 645,576 and 649,621, both granted in 1900. These are considered his first radio patents, which he stated were relevant to “energy of many thousands of horsepower [being] transmitted over vast distances”. In other words, he thought large amounts of electrical power could also be transmitted via this technology. At this stage, wireless power transmission was his main focus, rather than radio communications. Contrary to popular belief, Tesla did not invent radio and, unfortunately, did not have a good or correct understanding of the physics involved. In 1900, Guglielmo Marconi also applied for a US patent for radio, but it and subsequent revisions were rejected based on Tesla’s preexisting patents. However, in 1904, Marconi was granted US Patent 757,559 for radio, which he had applied for in 1901. Marconi had also previously applied for a British patent for radio in 1896, and it was granted in 1897, predating Tesla. The British patent (12,039) was the first for a system of wireless telegraphy using Hertzian waves. Marconi was thus recognised as the inventor of radio; he shared a Nobel prize for it in 1909 with Karl Braun. Of course, there were many other contributors to the invention of radio, such as Reginald Fessenden, Heinrich Hertz, Oliver Lodge and John Stone. There was litigation over early radio patents, and in 1943, the US Supreme Court settled a case involving Tesla’s patents. However, it was not, as is often claimed, a case about who invented radio but who would be compensated by the US Government for using various patents during WW1. The story is too complicated to go into here; see https://earlyradiohistory.us/tesla.htm Next month In the following article, we’ll pick up where we left off and cover the remainder of Tesla’s life, from 1898 until his passing in 1943. We’ll then go over related topics such as Tesla’s mistakes and misconceptions, why the World Wireless System could never work, the ‘war of the currents’ and Tesla’s lost files. PE 75