Coherer

The coherer was a primitive form of radio signal detector used in the first radio receivers during the wireless telegraphy era at the beginning of the 20th century. Its use in radio was based on the 1890 findings of French physicist Edouard Branly and adapted by other physicists and inventors over the next ten years. The device consists of a tube or capsule containing two electrodes spaced a small distance apart with loose metal filings in the space between. When a radio frequency signal is applied to the device, the metal particles would cling together or "cohere", reducing the initial high resistance of the device, thereby allowing a much greater direct current to flow through it. In a receiver, the current would activate a bell, or a Morse paper tape recorder to make a record of the received signal. The metal filings in the coherer remained conductive after the signal (pulse) ended so that the coherer had to be "decohered" by tapping it with a clapper actuated by an electromagnet, each time a signal was received, thereby restoring the coherer to its original state. Coherers remained in widespread use until about 1907, when they were replaced by more sensitive electrolytic and crystal detectors.

Coherer
Metal filings coherer designed by Guglielmo Marconi.

History

The behavior of particles or metal filings in the presence of electricity or electric sparks was noticed in many experiments well before Edouard Branly's 1890 paper and even before there was proof of the theory of electromagnetism.[1] In 1835 Swedish scientist Peter Samuel Munk[2] noticed a change of resistance in a mixture of metal filings in the presence of spark discharge from a Leyden jar.[3] In 1850 Pierre Guitard found that when dusty air was electrified, the particles would tend to collect in the form of strings. The idea that particles could react to electricity was used in English engineer Samuel Alfred Varley's 1866 lightning bridge, a lightning arrester attached to telegraph lines consisting of a piece of wood with two metal spikes extending into a chamber. The space was filled with powdered carbon that would not allow the low voltage telegraph signals to pass through but it would conduct and ground a high voltage lightning strike.[4] In 1879 the Welsh scientist David Edward Hughes found that loose contacts between a carbon rod and two carbon blocks as well as the metallic granules in a microphone he was developing responded to sparks generated in a nearby apparatus.[3] Temistocle Calzecchi-Onesti in Italy began studying the anomalous change in the resistance of thin metallic films and metal particles at Fermo/Monterubbiano. He found that copper filings between two brass plates would cling together, becoming conductive, when he applied a voltage to them. He also found that other types of metal filings would have the same reaction to electric sparks occurring at a distance, a phenomenon that he thought could be used for detecting lightning strikes.[4] Calzecchi-Onesti's papers were published in il Nuovo Cimento in 1884, 1885 and 1886.

Branly coherer
Branly's electrical circuit tube filled with iron filings (later called a "coherer")

In 1890, French physicist Edouard Branly published On the Changes in Resistance of Bodies under Different Electrical Conditions in a French Journal where he described his thorough investigation of the effect of minute electrical charges on metal and many types of metal filings. In one type of circuit, filings were placed in a tube of glass or ebonite, held between two metal plates. When an electric discharge was produced in the neighbourhood of the circuit, a large deviation was seen on the attached galvanometer needle. He noted the filings in the tube would react to the electric discharge even when the tube was placed in another room 20 yards away. Branly went on to devise many types of these devices based on "imperfect" metal contacts. Branly's filings tube came to light in 1892 in Great Britain when it was described by Dr. Dawson Turner at a meeting of the British Association in Edinburgh.[5][6] The Scottish electrical engineer and astronomer George Forbes suggested that Branly's filings tube might be reacting in the presence of Hertzian waves, a type of air-borne electromagnetic radiation proven to exist by German physicist Heinrich Hertz (later called radio waves).

Marconi's Coherer Receiver at Oxford Museum History of Science (cropped)
Marconi's 1896 coherer receiver, at the Oxford Museum of the History of Science, UK. The coherer is on right, with the decoherer mechanism behind it. The relay is in the cylindrical metal container (center) to shield the coherer from the RF noise from its contacts.

In 1893 physicist W.B. Croft exhibited Branly's experiments at a meeting of the Physical Society in London. It was unclear to Croft and others whether the filings in the Branly tube were reacting to sparks or the light from the sparks. George Minchin noticed the Branly tube might be reacting to Hertzian waves the same way his solar cell did and wrote the paper "The Action of Electromagnetic Radiation on Films containing Metallic Powders".[5][6] These papers were read by English physicist Oliver Lodge who saw this as a way to build a much improved Hertzian wave detector. On 1 June 1894, a few months after the death of Heinrich Hertz, Oliver Lodge delivered a memorial lecture on Hertz where he demonstrated the properties of "Hertzian waves" (radio), including transmitting them over a short distance, using an improved version of Branly's filings tube, which Lodge had named the "coherer", as a detector. In May 1895, after reading about Lodge's demonstrations, the Russian physicist Alexander Popov built a "Hertzian wave" (radio wave) based lightning detector using a coherer. That same year, Italian inventor Guglielmo Marconi demonstrated a wireless telegraphy system using Hertzian waves (radio), based on a coherer.

The coherer was replaced in receivers by the simpler and more sensitive electrolytic and crystal detectors around 1907, and became obsolete.

One minor use of the coherer in modern times was by Japanese tin-plate toy manufacturer Matsudaya Toy Co. who beginning 1957 used a spark-gap transmitter and coherer-based receiver in a range of radio-controlled (RC) toys, called Radicon (abbreviation for Radio-Controlled) toys. Several different types using the same RC system were commercially sold, including a Radicon Boat (very rare), Radicon Oldsmobile Car (rare) and a Radicon Bus (the most popular).[7][8]

Operation

Recepteur tube limaille
The circuit of a coherer receiver, that recorded the received code on a Morse paper tape recorder.

Unlike modern AM radio stations that transmit a continuous radio frequency, whose amplitude (power) is modulated by an audio signal, the first radio transmitters transmitted information by wireless telegraphy (radiotelegraphy), the transmitter was turned on and off (on-off keying) to produce different length pulses of unmodulated carrier wave signal, "dots" and "dashes", that spelled out text messages in Morse code. As a result, early radio receiving apparatus merely had to detect the presence or absence of the radio signal, not convert it to audio. The device that did this was called a detector. The coherer was the most successful of many detector devices that were tried in the early days of radio.

The operation of the coherer is based on the phenomenon of electrical contact resistance. Specifically as metal particles cohere (cling together), they conduct electricity much better after being subjected to radio frequency electricity. The radio signal from the antenna was applied directly across the coherer's electrodes. When the radio signal from a "dot" or "dash" came in, the coherer would become conductive. The coherer's electrodes were also attached to a DC circuit powered by a battery that created a "click" sound in earphones or a telegraph sounder, or a mark on a paper tape, to record the signal. Unfortunately, the reduction in the coherer's electrical resistance persisted after the radio signal was removed. This was a problem because the coherer had to be ready immediately to receive the next "dot" or "dash". Therefore, a decoherer mechanism was added to tap the coherer, mechanically disturbing the particles to reset it to the high resistance state.

Coherence of particles by radio waves is an obscure phenomenon that is not well understood even today. Recent experiments with particle coherers seem to have confirmed the hypothesis that the particles cohere by a micro-weld phenomenon caused by radio frequency electricity flowing across the small contact area between particles.[9][10] The underlying principle of so-called "imperfect contact" coherers is also not well understood, but may involve a kind of tunneling of charge carriers across an imperfect junction between conductors.

Application

The coherer as developed by Marconi consisted of metal filings (dots) enclosed between two slanted electrodes (black) a few millimeters apart, connected to terminals.

Cohere(Ag-Ni)
Coherer

The coherer used in practical receivers was a glass tube, sometimes evacuated, which was about half filled with sharply cut metal filings, often part silver and part nickel. Silver electrodes made contact with the metal particles on both ends. In some coherers, the electrodes were slanted so the width of the gap occupied by the filings could be varied by rotating the tube about its long axis, thus adjusting its sensitivity to the prevailing conditions.

In operation, the coherer is included in two separate electrical circuits. One is the antenna-ground circuit shown in the untuned receiver circuit diagram below. The other is the battery-sounder relay circuit including battery B1 and relay R in the diagram. A radio signal from the antenna-ground circuit "turns on" the coherer, enabling current flow in the battery-sounder circuit, activating the sounder, S. The coils, L, act as RF chokes to prevent the RF signal power from leaking away through the relay circuit.

Coherer Rcvr
A radio receiver circuit using a coherer detector (C). The "tapper" (decoherer) is not shown.

One electrode, A, of the coherer, (C, in the left diagram) is connected to the antenna and the other electrode, B, to ground. A series combination of a battery, B1, and a relay, R, is also attached to the two electrodes. When the signal from a spark gap transmitter is received, the filings tend to cling to each other, reducing the resistance of the coherer. When the coherer conducts better, battery B1 supplies enough current through the coherer to activate relay R, which connects battery B2 to the telegraph sounder S, giving an audible click. In some applications, a pair of headphones replaced the telegraph sounder, being much more sensitive to weak signals, or a Morse recorder which recorded the dots and dashes of the signal on paper tape.

Blondel coherer and Guarini decoherer
A coherer with electromagnet-operated "tapper" (decoherer), built by early radio researcher Emile Guarini around 1904.

The problem of the filings continuing to cling together and conduct after the removal of the signal was solved by tapping or shaking the coherer after the arrival of each signal, shaking the filings and raising the resistance of the coherer to the original value. This apparatus was called a decoherer. This process was referred to as 'decohering' the device and was subject to much innovation during the life of the popular use of this component. Tesla, for example, invented a coherer in which the tube rotated continually along its axis.

In later practical receivers the decoherer was a clapper similar to an electric bell, operated by an electromagnet powered by the coherer current itself. When the radio wave turned on the coherer, the DC current from the battery flowed through the electromagnet, pulling the arm over to give the coherer a tap. This returned the coherer to the nonconductive state, turning off the electromagnet current, and the arm sprang back. If the radio signal was still present, the coherer would immediately turn on again, pulling the clapper over to give it another tap, which would turn it off again. The result was a constant "trembling" of the clapper during the period that the radio signal was on, during the "dots" and "dashes" of the Morse code signal.

Imperfect junction coherer

There are several variations of what is known as the imperfect junction coherer. The principle of operation (microwelding) suggested above for the filings coherer may be less likely to apply to this type because there is no need for decohering. An iron and mercury variation on this device was used by Marconi for the first transatlantic radio message. An earlier form was invented by Jagdish Chandra Bose in 1899.[11] The device consisted of a small metallic cup containing a pool of mercury covered by a very thin insulating film of oil; above the surface of the oil, a small iron disc is suspended. By means of an adjusting screw the lower edge of the disc is made to touch the oil-covered mercury with a pressure small enough not to puncture the film of oil. Its principle of operation is not well understood. The action of detection occurs when the radio frequency signal somehow breaks down the insulating film of oil, allowing the device to conduct, operating the receiving sounder wired in series. This form of coherer is self-restoring and needs no decohering.

In 1899, Bose announced the development of an "iron-mercury-iron coherer with telephone detector" in a paper presented at the Royal Society, London.[12] He also later received U.S. Patent 755,840, "Detector for electrical disturbances" (1904), for a specific electromagnetic receiver.

Limitations of coherers

Coherers have difficulty discriminating between the impulsive signals of spark-gap transmitters, and other impulsive electrical noise:[13]

This device [the coherer] was publicized as wonderful, and it was wonderfully erratic and bad. It would not work when it should, and it worked overtime when it should not have.

— Robert Marriott

All was fish that came to the coherer net, and the recorder wrote down dot and dash combinations quite impartially for legitimate signals, static disturbances, a slipping trolley several blocks away, and even the turning on and off of lights in the building. Translation of the tape frequently required a brilliant imagination

Coherers were also finicky to adjust and not very sensitive. Another problem was that, because of the cumbersome mechanical "decohering" mechanism, the coherer was limited to a receiving speed of 12 - 15 words per minute of Morse code, while telegraph operators could send at rates of 50 WPM, and paper tape machines at 100 WPM.[14][15]

More important for the future, the coherer could not detect AM (radio) transmissions. As a simple switch that registered the presence or absence of radio waves, the coherer could detect the on-off keying of wireless telegraphy transmitters, but it could not demodulate (rectify) the waveforms of AM radiotelephone signals, which began to be experimented with in the first years of the 20th century. This problem was solved by the rectification capability of Reginald Fessenden's hot wire barretter and electrolytic detector. These were replaced by the crystal detector around 1906, and then around 1912 by vacuum tube technologies such as John Ambrose Fleming's thermionic diode and Lee De Forest's Audion (triode) tube.

Radioconducteur 1
One of the first coherers designed by Edouard Branly. Built by his assistant.
Radioconducteur 05
A "ball" coherer, designed by Branly in 1899. This imperfect contact type had a series of lightly touching metal balls set between two electrodes.
Trepied 01
Tripod coherer, built by Branly in 1902, another imperfect contact type. Although most coherers functioned as "switches" that turned on a DC current from a battery in the presence of radio waves, this may be one of the first rectifying (diode) detectors, because Branly reported it could produce a DC current without a battery.
Radioconducteur 07
Another tripod detector built by Branly

See also

Further reading

  • Phillips, Vivian J. (1980). Early Radio Wave Detectors. London: Inst. of Electrical Engineers. ISBN 0906048249.. A comprehensive description of radio detectors up to the development of the vacuum tube, with many unusual types of coherer.
  • Cuff, Thomas Mark (1993). Coherers, a review. Philadelphia, PA, Temple University, Master's Thesis. A technical historical account of the discovery and development of coherers and coherer-like behaviors from the 1800s to 1993, including the investigations, in the 1950s, of using coherers in the, then, new field of digital computers. This thesis examined the similarities among coherers and electrolytic RF detectors, MOM (Metal-Oxide-Metal) 'diodes' used in laser heterodyning, and the STM (Scanning Tunneling Microscope).

References

  1. ^ L. W. Turner, Electronics Engineer's Reference Book, Butterworth-Heinemann - 2013, pages 2-3, 2-4
  2. ^ Peter Samuel Munk af Rosenschold lecture assistant in Chemistry at the University of Lund was born at Lund in 1804 and died in 1860 (Michael Faraday, Christian Friedirich Schoenbein, The letters of Faraday and Schoenbein 1836-1862: With notes, comments and references to contemporary letters, Williams & Norgate - 1899, page 54)
  3. ^ a b Eric Falcon and Bernard Castaing, Electrical conductivity in granular media and Branly’s coherer: A simple experiment, page 1
  4. ^ a b T. K. Sarkar, Robert Mailloux, Arthur A. Oliner, M. Salazar-Palma, Dipak L. Sengupta, History of Wireless, John Wiley & Sons - 2006, pages 261-262
  5. ^ a b Sungook Hong, Wireless: From Marconi's Black-box to the Audion, page 4
  6. ^ a b E C Green, The Development of the Coherer And Some Theories of Coherer Action, Scientific American: Supplement, Volume 84 - 1917, page 268
  7. ^ Lee, Thomas H. (2004). Planar Microwave Engineering: A Practical Guide to Theory, Measurement, and Circuits. London: Cambridge University Press. p. 11. ISBN 0521835267.
  8. ^ Findlay, David A. (September 1, 1957). "Radio Controlled Toys Use Spark Gap" (PDF). Electronics. McGraw-Hill. 30 (9): 190. Retrieved November 11, 2015.
  9. ^ E. Falcon, B. Castaing, and M. Creyssels: Nonlinear electrical conductivity in a 1D granular medium, Laboratoire de Physique de l’Ecole Normale Sup'erieure de Lyon UMR 5672 -46 all'ee d’Italie, 69007 Lyon, France
  10. ^ Falcona, Eric; Bernard Castaing (April 2005). "Electrical conductivity in granular media and Branly's coherer: A simple experiment" (PDF). American Journal of Physics. USA: American Association of Physics Teachers. 73 (4): 302–306. arXiv:cond-mat/0407773. Bibcode:2005AmJPh..73..302F. doi:10.1119/1.1848114. Retrieved 14 November 2013.
  11. ^ Bose article by Varun Aggarwal
  12. ^ Bondyopadhyay (1988)
  13. ^ quoted in Douglas, Alan (April 1981). "The crystal detector". IEEE Spectrum. New York: Inst. of Electrical and Electronic Engineers: 64. Retrieved 2010-03-14. on Stay Tuned website
  14. ^ Maver, William Jr. (August 1904). "Wireless Telegraphy To-Day". American Monthly Review of Reviews. New York: The Review of Reviews Co. 30 (2): 192. Retrieved January 2, 2016.
  15. ^ Aitken, Hugh G.J. (2014). The Continuous Wave: Technology and American Radio, 1900-1932. Princeton Univ. Press. p. 190. ISBN 1400854601.

External links

Alexander Stepanovich Popov

Alexander Stepanovich Popov (sometimes spelled Popoff; Russian: Алекса́ндр Степа́нович Попо́в; March 16 [O.S. March 4] 1859 – January 13 [O.S. December 31, 1905] 1906) was a Russian physicist who is acclaimed in his homeland and some eastern European countries as the inventor of radio.Popov's work as a teacher at a Russian naval school led him to explore high frequency electrical phenomena. On May 7, 1895 he presented a paper on a wireless lightning detector he had built that worked via using a coherer to detect radio noise from lightning strikes. This day is celebrated in the Russian Federation as Radio Day. In a March 24, 1896 demonstration, he used radio waves to transmit a message between different campus buildings in St. Petersburg. His work was based on that of another physicist – Oliver Lodge, and contemporaneous with the work of Guglielmo Marconi. Marconi had just registered a patent with the description of the device two months after first transmission of radio signals made by Popov.

Amateur

An amateur, from French amateur "lover of", is generally considered a person who pursues a particular activity or field of study independently from their source of income. Amateurs and their pursuits are also described as popular, informal, self-taught, user-generated, DIY, and hobbyist.

Camille Tissot

Camille Papin Tissot (15 October 1868 – 2 October 1917) was a French naval officer and pioneer of wireless telegraphy who established the first French operational radio connections at sea.

Crystal detector

A crystal detector is an obsolete electronic component in some early 20th century radio receivers that used a piece of crystalline mineral as a detector (demodulator) to rectify the alternating current radio signal to extract the audio modulation which produced the sound in the earphones. It was the first type of semiconductor diode, and one of the first semiconductor electronic devices. The most common type was the so-called cat whisker detector, which consisted of a piece of crystalline mineral, usually galena (lead sulfide), with a fine wire touching its surface. The "asymmetric conduction" of electric current across electrical contacts between a crystal and a metal was discovered in 1874 by Karl Ferdinand Braun. Crystals were first used as radio wave detectors in 1894 by Jagadish Chandra Bose in his microwave experiments. who first patented a crystal detector in 1901. The crystal detector was developed into a practical radio component mainly by G. W. Pickard, who began research on detector materials in 1902 and found hundreds of substances that could be used in forming rectifying junctions. The physical principles by which they worked were not understood at the time they were used, but subsequent research into these primitive point contact semiconductor junctions in the 1930s and 1940s led to the development of modern semiconductor electronics.The unamplified radio receivers that used crystal detectors were called crystal radios. The crystal radio was the first type of radio receiver that was used by the general public, and became the most widely used type of radio until the 1920s. It became obsolete with the development of vacuum tube receivers around 1920, but continued to be used until World War 2.

Detector (radio)

In radio, a detector is a device or circuit that extracts information from a modulated radio frequency current or voltage. The term dates from the first three decades of radio (1888-1918). Unlike modern radio stations which transmit sound (an audio signal) on an uninterrupted carrier wave, early radio stations transmitted information by radiotelegraphy. The transmitter was switched on and off to produce long or short periods of radio waves, spelling out text messages in Morse code. Therefore, early radio receivers had only to distinguish between the presence or absence of a radio signal. The device that performed this function in the receiver circuit was called a detector. A variety of different detector devices, such as the coherer, electrolytic detector, magnetic detector and the crystal detector were used during the wireless telegraphy era until superseded by vacuum tube technology.

After sound (amplitude modulation, AM) transmission began around 1920, the term evolved to mean a demodulator, (usually a vacuum tube) which extracted the audio signal from the radio frequency carrier wave. This is its current meaning, although modern detectors usually consist of semiconductor diodes, transistors, or integrated circuits.

In a superheterodyne receiver the term is also sometimes used to refer to the mixer, the tube or transistor which converts the incoming radio frequency signal to the intermediate frequency. The mixer is called the first detector, while the demodulator that extracts the audio signal from the intermediate frequency is called the second detector.

In microwave and millimeter wave technology the terms detector and crystal detector refer to waveguide or coaxial transmission line components, used for power or SWR measurement, that typically incorporate point contact diodes or surface barrier Schottky diodes.

Electrolytic detector

The electrolytic detector, or liquid barretter, was a type of detector (demodulator) used in early radio receivers. First used by Canadian radio researcher Reginald Fessenden in 1903, it was used until about 1913, after which it was superseded by crystal detectors and vacuum tube detectors such as the Fleming valve and Audion (triode). It was considered very sensitive and reliable compared to other detectors available at the time such as the magnetic detector and the coherer. It was one of the first rectifying detectors, able to receive AM (sound) transmissions. On December 24, 1906, US Naval ships with radio receivers equipped with Fessendon's electrolytic detectors received the first AM radio broadcast from Fessenden's Brant Rock, Massachusetts transmitter, consisting of a program of Christmas music.

Guglielmo Marconi

Guglielmo Marconi, 1st Marquis of Marconi (Italian: [ɡuʎˈʎɛlmo marˈkoːni]; 25 April 1874 – 20 July 1937) was an Italian inventor and electrical engineer, known for his pioneering work on long-distance radio transmission, development of Marconi's law, and a radio telegraph system. He is credited as the inventor of radio, and he shared the 1909 Nobel Prize in Physics with Karl Ferdinand Braun "in recognition of their contributions to the development of wireless telegraphy".Marconi was also an entrepreneur, businessman, and founder of The Wireless Telegraph & Signal Company in the United Kingdom in 1897 (which became the Marconi Company). He succeeded in making an engineering and commercial success of radio by innovating and building on the work of previous experimenters and physicists. In 1929, Marconi was ennobled as a Marchese (marquis) by King Victor Emmanuel III of Italy, and, in 1931, he set up the Vatican Radio for Pope Pius XI.

Hot wire barretter

The hot wire barretter was a demodulating detector, invented in 1902 by Reginald Fessenden, that found limited use in early radio receivers. In effect it was a highly sensitive thermoresistor which could recover amplitude modulated signals, something that the coherer (the standard detector of the time) could not do.The first device used to demodulate audio signals, it was later superseded by the electrolytic detector, also generally attributed to Fessenden. The barretter principle is still used as a detector for microwave radiation, similar to a bolometer.

Institut supérieur d'électronique de Paris

ISEP, short for "Institut supérieur d’électronique de Paris", is a French Grande école located in Paris. It specializes in electronics, telecommunication and computer science. ISEP cultivates engineers of today and tomorrow, in the key areas of IT world:

Computer science & Cybersecurity – Electronics & Robotics – Telecommunications & Internet of Things (IoT) – Imaging & Health – Artificial Intelligence

The school was founded in 1955 on the place where Édouard Branly, physics professor at the Catholic University of Paris, discovered the coherer in 1890.

The school has two campuses, one in paris in the 6ème - located in the heart of Paris, next to the “Quartier Latin”, one in an outskirt named Issy les Moulineaux.

ISEP has three main departments (Electronics, Telecommunication, Information systems) and ten laboratories for teaching and research. ISEP has relationships with several companies in its industry (Thales, STMicroelectronics, ATMEL) and has a strong worldwide program orientation (co-operation agreements with more than 20 international institutions, member of 3 international exchange programs). ISEP also initiated an International master's degree program. ISEP welcomes a diverse range of international students at both undergraduate and postgraduate levels.

It is one amongst the top four Grandes écoles according to the French magazines l'Express and L'Étudiant in 2010. In 2015, the school was ranked best in France for "digital" related subject and best overall private school by l'Usine Nouvelle.. In 2018, ISEP was ranked at the top of the podium by L’Etudiant magazine (out of 174 institutions) for the criteria “Making a good living in information technology”. This underlines ISEP’s excellence, the strength of its engineering degree and its proximity to businesses and the professional world.

Invention of radio

The invention of radio communication, although generally attributed to Guglielmo Marconi in the 1890s, spanned many decades, from theoretical underpinnings, through proof of the phenomenon's existence, development of technical means, to its final use in signalling.

The idea that the wires needed for electrical telegraphy could be eliminated, creating a wireless telegraph, had been around for a while before radio based communication. Inventors attempted to build systems based on electric conduction, electromagnetic induction, or on their own theoretical ideas. Several inventors/experimenters came across radio waves before they were proven to exist but it was written off as electromagnetic induction at the time.

The discovery of electromagnetic waves, including radio waves, by Heinrich Rudolf Hertz in the 1880s came about after over a half century theoretical development on the connection between electricity and magnetism starting in the early 1800s and culminated in a theory of electromagnetism developed by James Clerk Maxwell by 1873, which Hertz finally proved.

The development of radio waves into a communication medium did not follow immediately afterwards. After their discovery Hertz considered them of little practical value and other experimenters who explored the physical properties of the new phenomenon, such as Oliver Lodge and Jagadish Chandra Bose, while transmitting radio waves some distance, did not seem to see any value in developing a communication system based on them. In their experiments they did develop electronic components and methods to improve the transmission and detection of electromagnetic waves.

In the mid 1890s, building on techniques physicists were using to study electromagnetic waves, Guglielmo Marconi developed the first apparatus for long distance radio communication. On 23 December 1900, the Canadian inventor Reginald A. Fessenden became the first person to send audio (wireless telephony) by means of electromagnetic waves, successfully transmitting over a distance of about 1.6 kilometers, and six years later on Christmas Eve 1906 he became the first person to make a public radio broadcast.By 1910 these various wireless systems had come to be referred to by the common name "radio".

Jagadish Chandra Bose

Sir Jagadish Chandra Bose, CSI, CIE, FRS (; Bengali: জগদীশ চন্দ্র বসু , IPA: [dʒɔɡodiʃ tʃɔndro bosu]; 30 November 1858 – 23 November 1937), also spelled Jagdish and Jagadis, was a polymath, physicist, biologist, biophysicist, botanist and archaeologist, and an early writer of science fiction from British India. He pioneered the investigation of radio and microwave optics, made significant contributions to plant science, and laid the foundations of experimental science in the Indian subcontinent. IEEE named him one of the fathers of radio science. Bose is considered the father of Bengali science fiction, and also invented the crescograph, a device for measuring the growth of plants. A crater on the moon has been named in his honour.Born in Munsiganj, Bengal Presidency (present-day Bangladesh), during British governance of India, Bose graduated from St. Xavier's College, Calcutta. He went to the University of London to study medicine, but could not pursue studies in medicine because of health problems. Instead, he conducted his research with the Nobel Laureate Lord Rayleigh at Cambridge and returned to India. He joined the Presidency College of the University of Calcutta as a professor of physics. There, despite racial discrimination and a lack of funding and equipment, Bose carried on his scientific research. He made remarkable progress in his research of remote wireless signalling and was the first to use semiconductor junctions to detect radio signals. However, instead of trying to gain commercial benefit from this invention, Bose made his inventions public in order to allow others to further develop his research.

Bose subsequently made a number of pioneering discoveries in plant physiology. He used his own invention, the crescograph, to measure plant response to various stimuli, and thereby scientifically proved parallelism between animal and plant tissues. Although Bose filed for a patent for one of his inventions because of peer pressure, his objections to any form of patenting was well known. To facilitate his research, he constructed automatic recorders capable of registering extremely slight movements; these instruments produced some striking results, such as quivering of injured plants, which Bose interpreted as a power of feeling in plants. His books include Response in the Living and Non-Living (1902) and The Nervous Mechanism of Plants (1926).

In 2004, Bose was ranked number 7 in BBC's poll of the Greatest Bengali of all time.

List of IEEE milestones

This list of IEEE Milestones describes the Institute of Electrical and Electronics Engineers (IEEE) milestones, representing key historical achievements in electrical and electronic engineering.

Prior to 1800

1751 – Book Experiments and Observations on Electricity by Benjamin Franklin

1757–1775 – Benjamin Franklin's Work in London

1799 – Volta's Electrical Battery Invention

1800–1850

1836 – Callan's Pioneering Contributions to Electrical Science and Technology

1828–1837 – Schilling's Pioneering Contribution to Practical Telegraphy

1838 – Demonstration of Practical Telegraphy1850–1870

1852 – Electric Fire Alarm System

1861–1870 – Maxwell's Equations

1861 – Transcontinental Telegraph

1866 – Landing of the Transatlantic Cable

1866 – County Kerry Transatlantic Cable Stations

1870–1890

1876 – First Intelligible Voice Transmission over Electric Wire

1876 – First Distant Speech Transmission in Canada

1876 – Thomas Alva Edison Historic Site at Menlo Park

1882 – Vulcan Street Plant

1882 – Pearl Street Station

1882 – First Central Station in South Carolina

1884 – First AIEE Technical Meeting

1886 – Alternating Current Electrification (demonstrated by William Stanley, Jr.)

1886 – First Generation and Experimental Proof of Electromagnetic Waves

1887 – Thomas A. Edison West Orange Laboratories and Factories

1887 – Weston Meters, first portable current and voltage meters

1888 – Richmond Union Passenger Railway

1889 – Power System of Boston's Rapid Transit

1890–1900

1890 – Discovery of Radioconduction with a Coherer by Édouard Branly

1890 – Keage Power Station, Japan's First Commercial Hydroelectric Plant

1891 – Ames Hydroelectric Generating Plant

1893 – Birth and Growth of Battery Industries in Japan

1893 – Mill Creek No. 1 Hydroelectric Plant

1894 – Millimeter-wave Communication Experiments by Jagadish Chandra Bose

1895 – Popov's Contribution to the Development of Wireless Communication

1895 – Adams Hydroelectric Generating Plant

1895 – Krka-Šibenik Electric Power System

1895 – Guglielmo Marconi's Experiments in Wireless Telegraphy

1895 – Electrification by Baltimore and Ohio Railroad

1897 – Early Swiss Wireless Experiments that sent a signal over one and a half kilometers.

1897 – Chivilingo Hydroelectric Plant

1898 – Decew Falls Hydro-Electric Plant

1898 – Rheinfelden Hydroelectric Power Plant

1899 – First Operational Use Of Wireless Telegraphy in the Anglo-Boer War

1900–1920

1900 – Georgetown Steam Hydro Generating Plant

1901 – Transmission of Transatlantic Radio Signals

1901 – Reception of Transatlantic Radio Signals

1901 – Early Developments in Remote-Control by Leonardo Torres-Quevedo

1902 – Poulsen-Arc Radio Transmitter

1903 – Vucje Hydroelectric Plant

1904 – Alexanderson Radio Alternator

1904 – Fleming Valve

1906 – Pinawa Hydroelectric Power Project

1906 – First Wireless Radio Broadcast by Reginald A. Fessenden

1906 – Grand Central Terminal Electrification

1907 – Alternating-Current Electrification of the New York, New Haven & Hartford Railroad

1909 – Shoshone Transmission Line

1911 – Discovery of superconductivity

1914 – Panama Canal Electrical and Control Installations

1920–1930

1920 – Westinghouse Radio Station KDKA (AM)

1920 – Funkerberg Königs Wusterhausen first radio broadcast in Germany

1924 – Directive Short Wave Antenna (Yagi-Uda antenna)

1924 – Enrico Fermi's Major Contribution to Semiconductor Statistics

1924–1941 – Development of Electronic Television

1925 – Bell Telephone Laboratories

1928 – One-Way Police Radio Communication

1929 – Shannon Scheme for the Electrification of the Irish Free State

1929 – Yosami Radio Transmitting Station

1929 – Largest Private (dc) Generating Plant in the U.S.A.

1929 – First Blind Takeoff, Flight and Landing

1930–1950

1930–1945 – Development of Ferrite Materials and Their Applications

1931 – Invention of Stereo Sound Reproduction

1932 – First Breaking of Enigma Code by the Team of Polish Cipher Bureau

1933 – Two-Way Police Radio Communication

1934 – Long-Range Shortwave Voice Transmissions from Byrd's Antarctic Expedition

1937 – Westinghouse "Atom Smasher"

1939 – Atanasoff–Berry Computer

1939 – Shannon Development of Information Theory

1939 – Single-element Unidirectional Microphone - Shure Unidyne

1940 – FM Police Radio Communication

1941 – Opana Radar Site

1939–1945 – Code-breaking at Bletchley Park during World War II

1940–1945 – MIT Radiation Laboratory

1942–1945 – US Naval Computing Machine Laboratory

1945 – Merrill Wheel-Balancing System

1945 – Rincón del Bonete Plant and Transmission System

1946 – Electronic Numerical Integrator and Computer (ENIAC)

1947 – Invention of the First Transistor at Bell Telephone Laboratories, Inc.

1947 – Invention of Holography

1948 – Birth of the Barcode

1950–1960

1950 – First External Cardiac Pacemaker

1951 – Manufacture of Transistors

1951 – Experimental Breeder Reactor I

1946–1953 – Monochrome-Compatible Electronic Color Television

1955 – WEIZAC Computer

1956 – RAMAC

1956 – Ampex Videotape Recorder

1956 – The First Submarine Transatlantic Telephone Cable System (TAT-1)

1957–1958 – First Wearable Cardiac Pacemaker

1958 – First Semiconductor Integrated Circuit (IC)

1959 – Semiconductor Planar Process and Integrated Circuit

1960–1970

1960–1984 – IBM Thomas J. Watson Research Center

1961–1964 – First Optical Fiber Laser and Amplifier

1962 – Mercury spacecraft MA-6, Col. John Glenn piloted the Mercury Friendship 7 spacecraft in the first United States human-orbital flight on 20 February 1962. (1)

1962 – Stanford Linear Accelerator Center

1962 – First Transatlantic Transmission of a Television Signal via Satellite

1962 – First Transatlantic Television Signal via Satellite

1962 – First Transatlantic Reception of a Television Signal via Satellite

1962 – Alouette-ISIS Satellite Program

1963 – NAIC/Arecibo Radiotelescope

1963 – First Transpacific Reception of a Television (TV) Signal via Satellite

1963 – Taum Sauk Pumped-Storage Electric Power Plant

1963 – ASCII

1964 – Mount Fuji Radar System

1964 – Tokaido Shinkansen (Bullet Train)

1964 – High-definition television

1964 – TPC-1 Transpacific Cable System

1965 – First 735 kV AC Transmission System

1965 – Dadda multiplier

1962–1967 – Pioneering Work on the Quartz Electronic Wristwatch

1966 – Interactive Video Games

1966 – Shakey, the first mobile robot to be able to reason about its own actions

1967 – First Astronomical Observations Using Very Long Baseline Interferometry

1968 – Liquid Crystal Display by George H. Heilmeier

1968 – CERN Experimental Instrumentation

1969 – Birth of the Internet

1969 – Inception of the ARPANET

1950–1969 – Electronic Technology for Space Rocket Launches

1969 – Electronic Quartz Wristwatch

1970–present

1965–1971 – Railroad Ticketing Examining System (developed by OMRON of Japan)

1970 - SPICE Circuit Simulation Program

1972 – Nelson River HVDC Transmission System

1964–1973 – Pioneering Work on Electronic Calculators

1971–1978 – The First Word Processor for the Japanese Language

1972 – Development of the HP-35, the First Handheld Scientific Calculator

1974 – Birth of CP/M Operating System

1975 – Gapless Metal Oxide Surge Arrester (MOSA) for electric power systems

1975 – Line Spectrum Pair (LSP) for high-compression speech coding

1976 – Development of VHS, a World Standard for Home Video Recording

1976 – Introduction of the Apple I Computer

1977 – Introduction of the Apple II Computer

1977 – Lempel–Ziv Data Compression Algorithm

1977 – Vapor-phase Axial Deposition Method for Mass Production of High-quality Optical Fiber

1978 – Digital Image from Synthetic Aperture Radar

1978 – Speak & Spell, the First Use of a Digital Signal Processing IC for Speech Generation

1979 – Compact Disc Audio Player

1979 – 20-inch Diameter Photomultiplier Tubes

1980 – International Standardization of Group 3 Facsimile

1980 – RISC (Reduced Instruction-Set Computing) Microprocessor

1981 – 16-Bit Monolithic Digital-to-Analog Converter (DAC) for Digital Audio

1981 – Map-Based Automotive Navigation System

1984 – First Direct-broadcast satellite Service

1984 – The MU (Middle and Upper atmosphere) radar

1985 – Toshiba T1100, for Contribution to the Development of Laptop PCs

1985 – Emergency Warning Code Signal Broadcasting System

1987 – High Temperature Superconductor

1987 – SPARC RISC Architecture

1988 – Sharp 14-Inch Thin Film Transistor Liquid-Crystal Display (TFT-LCD) for TV

1988 – Solid State High Voltage DC Converter Station

1988 – Trans-Atlantic Telephone Fiber-optic Submarine Cable, TAT-8

1988 – Virginia Smith High-Voltage Direct-Current Converter Station

1989 – Development of CDMA for Cellular CommunicationsSpecial citations

1856–1943 – Nikola Tesla, Electrical Pioneer

1979 – Computer History Museum

Musée Edouard Branly

The Musée Édouard Branly is a museum dedicated to the work of radio pioneer Édouard Branly (1844-1940). It is located in the 6th arrondissement at the Institut Catholique de Paris-ISEP, 21, rue d'Assas, Paris, France, and open by appointment only.The museum contains the research laboratory and equipment used by Édouard Branly, a physics professor at the Institut Catholique de Paris and inventor of the first widely used radio receiver, the Branly coherer circa 1884-1886. Its collection includes a number of early devices used in wireless experiments, such as electrolytic detectors, insulated tubes filled with metal filings, a Righi oscillator, generators, electromagnets, metallic blades mounted on glass, electrical contacts, and a column of six steel balls stacked in a glass cylinder.

Oliver Lodge

For the British poet and author (1878–1955), see Oliver W. F. Lodge

Sir Oliver Joseph Lodge, (12 June 1851 – 22 August 1940) was a British physicist and writer involved in the development of, and holder of key patents for, radio. He identified electromagnetic radiation independent of Hertz' proof and at his 1894 Royal Institution lectures ("The Work of Hertz and Some of His Successors"), Lodge demonstrated an early radio wave detector he named the "coherer". In 1898 he was awarded the "syntonic" (or tuning) patent by the United States Patent Office. Lodge was Principal of the University of Birmingham from 1900 to 1920.

Radio receiver

In radio communications, a radio receiver, also known as a receiver, wireless or simply radio is an electronic device that receives radio waves and converts the information carried by them to a usable form. It is used with an antenna. The antenna intercepts radio waves (electromagnetic waves) and converts them to tiny alternating currents which are applied to the receiver, and the receiver extracts the desired information. The receiver uses electronic filters to separate the desired radio frequency signal from all the other signals picked up by the antenna, an electronic amplifier to increase the power of the signal for further processing, and finally recovers the desired information through demodulation.

The information produced by the receiver may be in the form of sound, moving images (television), or data. A radio receiver may be a separate piece of electronic equipment, or an electronic circuit within another device. Radio receivers are very widely used in modern technology, as components of communications, broadcasting, remote control, and wireless networking systems.

In consumer electronics, the terms radio and radio receiver are often used specifically for receivers designed to reproduce sound transmitted by radio broadcasting stations, historically the first mass-market commercial radio application.

Temistocle Calzecchi-Onesti

Temistocle Calzecchi Onesti (December 14, 1853 – November 25, 1922) was an Italian physicist and inventor born in Lapedona, Italy, where his father, Icilio Calzecchi, a medical doctor from nearby Monterubbiano, was temporarily working at the time. His mother, Angela, was the last descendant of the ancient and noble Onesti family. His first name is the Italian version of the Athenian general Themistocles.

Calzecchi demonstrated in experiments in 1884 through 1886 that iron filings contained in an insulating tube will conduct an electric current under the action of an electromagnetic wave. This discovery was the operating principle behind an early radio wave detector device called the coherer, developed about 6–10 years later by Oliver Lodge, Edouard Branly, and Guglielmo Marconi, which was influential in the development of radio.

Thomas Tommasina

Thomas Tommasina (1855 – 29 January 1935) was an artist turned physicist who worked on atmospheric ionization and gravitational theories mainly after moving to Switzerland. An experimenter as well as a theoretician, he invented a radio-receiver-like device while studying ionospheric disturbances in the upper atmosphere and used it in long-range weather prediction.

Tommasina was born in the town of Intra (today part of Verbania) on the shores of Lake Maggiore in the Kingdom of Lombardy–Venetia. In his early years, he admired the Italian school of painting, particularly that of Leonardo da Vinci and went to study art. In 1885 he became inspired by the works of Alessandro Volta, took an interest in physics and went to Geneva to study under Charles Soret. Here he worked on the physics behind the hardness of solids. Following the works of Julius Elster and Hans Friedrich Geitel he joined Édouard Sarasin in studies on the ionization of air and related phenomena. He was a doctor of science and member of the National Institute of Geneva from 1902. He wrote a book on the "physics of gravitation and dynamic of the Universe" ("La Physique de la Gravitation et la Dynamique de l'Univers") in 1927. He also worked on the orbits of comets during this period. His work on gravity using wave models was founded on the idea of ether. He also wrote an introduction to a French translation of a book by Alfred Russel Wallace in 1907 - "La place de l'homme dans l'univers : études sur les résultats des recherches scientifiques, sur l'unité et la pluralité des mondes".

Tommasina invented a telephonic receiver system which he adapted as a weather forecasting system in 1901. Called the "Electro-radiophone" it picked up electric discharges in the atmosphere and transmitted them over wires to where it could be heard in the form of sound. The receiver made use of the Branly effect. It may have been one of the earliest ideas on using wireless telegraphy in meteorology. Tommasina's device had also been of interest to Guglielmo Marconi. When Marconi claimed a patent there were several counter-claims and it was suggested that the true inventor of the so-called "mercury-coherer" used in the first transatlantic telegraphy was Tommasina. Tommasina did not however use it for the purpose of wireless-telegraphy nor did he claim to be its inventor.Tommasina died at his villa in Champel on 29 January 1935.

Timeline of radio

The timeline of radio lists within the history of radio, the technology and events that produced instruments that use radio waves and activities that people undertook. Later, the history is dominated by programming and contents, which is closer to general history.

Édouard Branly

Édouard Eugène Désiré Branly (23 October 1844 – 24 March 1940) was a French inventor, physicist and professor at the Institut Catholique de Paris. He is primarily known for his early involvement in wireless telegraphy and his invention of the Branly coherer around 1890.

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