A Thumbnail History of Electronics
I. Cathode Rays & the Discovery of the Electron
Although many of the pioneers of 19th Century physics, including Faraday, were convinced on the basis of chemistry and the phenomena observed in electrolysis that electric current consisted of the flow of particles of charge, the nature of these charges was not understood. Even the basic question of whether the charge of the particles was positive or negative remained undetermined. The answers to these questions, and to the basic structure of matter, were resolved by experiments that began with the study of electric discharges in evacuated tubes. Along the way a series of discoveries were made which led to the technological revolution of the 20th Century.
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William Crookes (1832-1919), heir at an early age to a large fortune, carried out his investigations in a private laboratory. His studies of electrical discharges in gases, which followed the development of the cathode ray tube by Pluecker and Hittorf, and his observations of cathode rays and the dark space at the cathode led to the discovery of x-rays and of the electron. Crookes also invented the radiometer, whose eventual explication verified the kinetic theory of gases. Curiously, Crookes was a believer in the occult and in the 1870’s claimed to have verified the authenticity of psychic phenomena. Later he became involved in the Theosophical Movement and there are references to his having exorcised demons. In 1897 Crookes was knighted by Queen Victoria (who is also reputed to have had an interest in the occult) and in 1909 was elected president of the Royal Society.
Karl Ferdinand Braun (1850-1918) was director of the Physical Institute and a professor of Physics at the University of Strasbourg when he demonstrated the first cathode ray tube oscillograph, guiding a narrow stream of electrons to a fluorescent screen and presaging the modern television screen. Although little remembered today, Braun made several important contributions. He discovered that rectification occurs at a crystal/metal junction, leading to the introduction of crystal receivers. In 1899, he introduced (sparkless) inductive coupling to antennas and the first directive beam antenna. He received the Nobel Prize in 1909 along with Guglielmo Marconi. Braun was in New York to testify in a patent suit when the United States entered World War I; he was interned as an enemy alien and died before the war ended.
Wilhelm Conrad Roentgen (1845 -1923) was 44 years old, head of the Physical Institute and recently retired Rector (President) of the University of Wurzburg when, in November, 1895, he discovered that some unknown radiation coming from a Crookes tube could cause crystals to fluoresce, pass through solid objects, and affect photographic plates. Working alone, sometimes sleeping in his laboratory, and maintaining great secrecy, he completed his research and eight weeks later announced his discovery. The scientific and medical implications of his work were immediately recognized and reported world-wide following its publication on New Year’s Day in 1896. Within a few weeks some hospitals began to use x-rays. Roentgen became one of the most renowned scientists in the world. He received many honors, including the first Nobel prize in Physics and an offer (refused) to be raised to the nobility.
J(oseph) J(ohn) Thomson (1856-1940), the son of a Manchester bookseller, entered college at fourteen and at twenty-eight was elected a fellow of the Royal Society and appointed to the Chair of Physics at the Cavendish Laboratory. His great discovery occurred in 1897 during the course of his investigations of cathode rays. Thomson provided convincing evidence that the rays consisted of charged particles; he measured the ratio of charge to mass and was able to estimate that the mass was equal to about 1/1800 of the mass of a hydrogen atom. His discovery of the electron won the Nobel Prize in 1906 and he was knighted two years later. Thomson was described by Rutherford as having "a most radiating smile, … when he is scoring off anyone."
Robert A. Millikan (1868 -1953) began his career as a classics major at Oberlin College, but agreed to teach Physics in order to earn more money. When he was offered a fellowship in Physics at Columbia he accepted, but again only because it was the best offer he could get financially. His academic career at the University of Chicago was at first devoted to teaching and administration and he did not begin to do research seriously until he was almost forty. Then, in 1906 he began to devise a series of improvements to the Thomson experiment that led to the oil-drop apparatus in which the charge of the electron was measured conclusively. His results were published in 1910 and the last resistance to the atomic theory of matter was dispelled. In 1914 he published the results of the research for which he was awarded the Nobel Prize - the direct determination of Plank’s constant using the photoelectric effect - verifying the 1905 Einstein theory of the photoelectric effect and the quantum nature of light.
II. Wireless Telegraphy
Maxwell's 1865 publication of a theory which unified electrodynamics, magnetodynamics, and optics had seemingly little impact in Britain where it was not widely accepted. Surprisingly, during the remaining fourteen years of his life, Maxwell, who was a skillful experimentalist, did not attempt to verify the existence of the electromagnetic waves that his theory predicted. However, the leading German scientist of the period, von Helmholtz, believed the Maxwell theory and he set his pupil Hertz on the track of producing and detecting electromagnetic radiation, opening the path to wireless communication.
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Heinrich Rudolf Hertz (1857-1894), a professor of physics at Karlsruhe Polytechnic, was the first to broadcast and receive radio waves in the laboratory. Between 1885 and 1889, he used spark discharges to produce electromagnetic waves. Hertz's radiator consisted of a pair of aligned rods, with a spark gap between them and capacitative plates at their ends. His receiver was a loop of wire with a small gap across which a small spark could be observed when the radiator discharged. Herz died suddenly of a brain tumor when he was thirty six, perhaps never realizing that transmission and reception over long distances was possible.
Edouard Eugène Désiré Branly (1844-1940) is revered in France as the inventor of wireless telegraphy. In 1890, Branly, a professor of Physics at the Catholic University of Paris, discovered that when exposed to even a distant spark transmission field, loose zinc and silver filings would cohere and provide a path of increased conductivity that could be used to detect the presence of the transmission. The "coherer" took radio transmission out of the laboratory and made communication over long distances possible.
Oliver Joseph Lodge (1851-1940) held the chair in Physics at the University College in Liverpool when he demonstrated a practical form of the Branly coherer in 1894. Lodge added a device that shook the filings loose between spark receptions. It became a standard device in early wireless telegraphy. Lodge also obtained the first patents for the use of tuned circuits to adjust the frequency of receivers and transmitters. After 1900, however, Lodge devoted himself to psychic research and attempts to communicate with the dead. In 1902 he was appointed the first principal of the new Birmingham University.
Guglielmo Marconi (1874-1937) failed the entrance exams to the Italian Naval Academy and the University of Bologna but was allowed by a family friend to attend lectures and laboratory at the university. In 1896, at age twenty-two, he patented a successful system of radio telegraphy . In the following years he introduced a notable series of inventions and ingenious redesigns of transmitting and receiving system components. In 1901 Marconi succeeded in receiving signals transmitted across the Atlantic Ocean. It may be fairly said that Marconi single-handedly advanced the development of radio telegraphy by decades. Marconi's Wireless Telegraphy Company soon established a net of coast stations in Britain for ship-to-shore communication. These were taken over by the British General Post Office in 1910, but for more than a decade the Marconi Company enjoyed a monopoly on maritime radio equipment sales by virtue of an agreement with Lloyds of London to only insure ships that used their equipment. In 1909 Marconi received the Nobel Prize for Physics.
III. VacuumTubes
The Edison effect, the appearance of an electric current flowing between a heated cathode and an anode in an evacuated tube, was a mysterious phenomenon when it was discovered in 1882; it was not understood how electric current could pass through a vacuum. Thomson's identification of cathode rays as streams of electrons resolved the mystery and led to the invention of the thermionic diode by Fleming. The diode, intended to serve as a rectifier to detect radiotelegraphic signals, had little impact as the coherer, invented by Branly and Lodge, and crystal and magnetic detectors continued to be used. The invention of the triode by DeForest, however, did revolutionize radio communication.
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Thomas Alva Edison (1847-1931) was owner or co-owner of a record 1,093 patents. He also invented the modern industrial research laboratory. In 1882, when one of his engineers, William Hammer, observed the "Edison Effect" during the course of experiments about the incandescent lamp, Edison, for reasons which he could not later explain, uncharacteristically did not follow up on the discovery. But, as he later admitted, at the time he did not even understand Ohm's law. The Edison effect remained an unexplained curiosity for fifteen years until the discovery of the electron.
John Ambrose Fleming (1849-1945) had a remarkable career which spanned the first seventy-five years of the development of electronics. Fleming was a student of Maxwell’s who later worked as a consultant for Edison and then Marconi. In 1904, following Edison’s observation of the passage of current from the filament to an anode in a light bulb and J.J. Thomson’s discovery that cathode rays consisted of charged particles, Fleming invented and patented the first electronic rectifier, the diode, or Fleming Valve. The device was intended for use in detecting the spark-generated radio waves of the time, replacing the other devices used by the pioneers of radio communication. Fleming was knighted in 1929.
Lee De Forest(1873-1961), son of a Congregational minister who was president of the Talledega College for Negroes in Alabama, lived a long life full of controversy. He was defrauded by partners, was involved in numerous patent suits, went through two divorces, and once was indicted (but later acquitted) for mail fraud for seeking to sell a worthless device (his audion tube), De Forest held more than 300 patents but is most remembered for initiating the electronic revolution with his 1906 invention of the audion tube, a three-element vacuum tube in which the grid controlled the current, which made modern radio possible. In 1912 he conceived the idea of cascading triodes to achieve high amplification and also independently discovered regenerative feedback.
William D. Coolidge (1873-1975), an electrical engineering graduate of MIT and the University of Leipzig, joined the General Electric Research Lab after a brief career in Academia. In 1911, he succeeded in fabricating a ductile form of tungsten which provided the filaments for modern incandescent lamps and also patented a thoriated cathode with improved emission for use in vacuum tubes. In 1913 Coolidge invented a hot-tungsten filament x-ray tube which provided a more penetrating and reliable source for radiology. The "Coolidge tube" became the standard generator of medical x-rays.
Walter Schottky (1886-1976) discovered the random noise due to the irregular arrival of electrons at the anode of thermionic tubes that is called "shot noise" (Schottky effect) in 1914 while studying under Planck in Berlin. Schottky was Swiss, but he was educated and spent his professional career in Germany. In 1919 he invented the first multiple grid vacuum tube, the tetrode. Schottky obtained multiple doctoral degrees, taught at universities from 1920 to 1927, and then worked for Siemans for nearly five decades. He was the first to note the existence of "holes" in the band structure of semiconductors, discovered the type of lattice vacancy known as the Schottky defect, and in 1938 created a theory that explained rectification at a metal/semiconductor interface.
Irving Langmuir (1881-1957), son of a struggling Brooklyn businessman, showed a precocious interest in Science. He received his degrees in Chemistry, but, tiring of the endless round teaching elementary courses and paper grading required of professors, left academia and went to the General Electric Research Laboratory. His work on molecular films won the Nobel Prize in Chemistry in 1932, and his studies on hot filaments in gases became the basis for improvements in incandescent lighting and a huge industry. His discoveries about the emission of electrons from cathodes and their behavior in vacuum tubes formed the basis for the design of a variety of tube types.
IV. Radio
Speech transmission using a spark transmitter was demonstrated by Fessenden in 1900 but was too noisy; in 1906 he broadcast the first program of speech and music using 50 KHz generated by an alternator. Fessenden also discovered the heterodyne principle of mixing a low frequency signal with the high frequency carrier. The 1913 discovery by De Forest and Armstrong of regenerative feedback and how to use the triode as an oscillator made commercial radio possible. Armstrong’s invention of the superheterodyne receiver in 1917 and FM in 1933 brought radio into the modern era. However, the technical triumphs were marred by years of bitter patent suits between all the participants and led to great personal tragedies.
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Reginald Aubrey Fessenden (1866-1932) was a Canadian-American who first worked for Edison. In 1900, while working for the U.S. Weather Bureau, he developed the ideas of continuous wave transmission and amplitude modulation and the heterodyne principle to permit speech transmission. After 1902, he directed the development of a one kilowatt, 50 kHz alternator to replace the spark transmitter, and invented an electrolytic detector for continuous waves. In December 1906 he realized the first radio-telephonic broadcast. Fessenden held hundreds of radio patents and also invented a variety of devices which included the radio compass and the fathometer. He was described as "a stormy and colorful figure" and for years he was deeply involved in a series of litigations against his patents.
Edwin Howard Armstrong (1890-1954) was a junior engineering student at Columbia in 1912 when he invented regenerative feedback and electronic oscillators. Although a later corporate suit brought by De Forest, led to the courts decision in favor of De Forest, the engineering community has continued to regard Armstrong as the inventor. Then in 1917 while serving in the army, Armstrong invented the superheterodyne receiver which is the basis for virtually all modern radio and radar communication systems. This patent was not disputed and Armstrong became a millionaire. Armstrong’s third invention was the superregenerative detector. Then, in 1933 Armstrong obtained a series of patents covering his invention of (wideband) FM, a new system of radio communication. The radio industry, with a vested interest in AM, had no interest in FM and Armstrong had to build the first station himself. FM slowly gained acceptance, but Armstrong, impoverished and embroiled in more patent suits, committed suicide.
Louis Alan Hazeltine (1886-1964) became head of the Electrical Engineering Department at Stevens Institute of Technology in 1917; this was the department which had awarded him his bachelor’s degree only eleven years before. During World War I, he designed a radio receiver for the U.S. Navy. In 1922, Hazeltine invented the "neutrodyne" receiver to eliminate the squeaks and howls of the early radio receivers. The Hazeltine amplifier neutralized the grid-to-plate capacitative coupling which was a cause of oscillation in triode amplifiers. The neutrodyne was the first commercial receiver suited to general public broadcast reception. By 1927 some ten million of these receivers were being used by listeners in the U.S.
Harold Stephen Black (1898-1983) worked, after graduation from Worcester Polytechnic, for a department of Western Electric Company which later became Bell Telephone Laboraotories. For six years he pursued a seemingly futile project to improve the distortion characteristics of amplifiers. In a storied incident, the answer was conceived in a creative flash during a commuter ride on a ferry in 1927. He wrote the equations on a blank page in his daily newspaper. Although at first it seemed paradoxical, negative feedback effected an extraordinary performance in amplifier performance.
V. Television
The pioneers of television were the Russians, Nipkow who invented a mechanical revolving scanning disk in 1884 and Rosing who used a cathode ray tube in 1907 to display images from a mechanical transmitter. In Britain in 1923, John Logie Baird began to demonstrate television transmission using Nipkow disks. In America, Rosing’s student, Vladimir Zworykin, filed a patent for an electronic television system in 1923, but the project was dropped by Westinghouse and Zworykin had to wait for RCA to restart the project in 1930. Meanwhile, an Idaho schoolboy, Philo Farnsworth, invented an electronic system in 1922, and by 1927 had transmitted television images. The development of the kinescope and its successor, the image orthicon tube, at RCA, plus a licensing agreement between RCA and Farnsworth led to the first appearance of commercial TV in April,1939 at the RCA pavilion at the New York World Fair.
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John Logie Baird (1888 -1946) graduated from the University of Glasgow and worked for a while as an engineer for a Glasgow electrical company, but was discharged when he blacked out half the city in an unauthorized experiment to create diamonds. In the 1920’s Baird began working on television using the Nipkow mechanical scanning disk. In 1926 he demonstrated the first television. He went on to demonstrate the first color and stereo televisions and succeeded in recording his video signals on disks. From 1929 to 1935, the BBC used the Baird mechanical television system; in the last part of this period it shared time with the electronic system. Mechanical systems, however, were limited to about 200 lines per frame and could not compete successfully against electronic systems.
Philo Taylor Farnsworth (1906-1971), was a 15-year old Mormon high school student in Rigby, Idaho in 1922 when he invented an electronic television system and explained it to his chemistry teacher. In 1926, at age 19, he received some backing and formed a company to develop television. By 1927 he had obtained his first patents, obtained financing from a group of San Francisco bankers, and displayed the first electronic television image. His success was announced in 1928, the first public demonstration was given in 1934, and by 1936 his studio was broadcasting to about fifty home receivers in Philadelphia. The next years were an odyssey of litigation as RCA tried to break the Farnsworth patents which blocked the kinescope and orthicon tubes. The Farnsworth patents were repeatedly upheld and in 1939 RCA agreed to pay royalties to the Farnsworth company.