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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 Édouard 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 electrom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 Édouard 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 electrom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crystal Detector
A crystal detector is an obsolete electronic component used in some early 20th century radio receivers that consists of a piece of crystalline mineral which rectifies the alternating current radio signal. It was employed as a detector ( demodulator) to extract the audio modulation signal from the modulated carrier, to produce 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's whisker detector, which consisted of a piece of crystalline mineral, usually galena (lead sulfide), with a fine wire touching its surface. Greenleaf Whittier Pickard, ''Detector for Wireless Telegraphy and Telephony'', filed: 21 June 1911, granted: 21 July 1914 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 Jaga ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Receiver
In radio communications, a radio receiver, also known as a receiver, a wireless, or simply a 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 of radio frequency) 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. Radio receivers are essential components of all systems that use radio. The information produced by the receiver may be in the form of sound, video (television), or digital data. A radio receiver may be a separate piece of electronic equipment, or an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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. Biography He was born on 23 October 1844 and died on 24 March 1940. His funeral was at the Notre Dame cathedral in Paris and was attended by the President of France, Albert Lebrun. He was interred in Père Lachaise Cemetery in Paris. Coherer Temistocle Calzecchi-Onesti's experiments with tubes of metal filings, as reported in "Il Nuovo Cimento" in 1884, led to the development of the first radio wave detector, the ''coherer'', by Branly some years later. It was the first widely used detector for radio communication. This consisted of iron filings contained in an insulating tube with two electrodes that will conduct an electric current under the action of an applied electrical signal. The operation of the cohe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 Fessenden's electrolytic detectors received the first AM radio broadcast from Fessenden's Brant Rock, Massachusetts transmitter, consisting of a program of Christmas music. History Fessenden, more than any other person, is responsible for developing amplitude modulation (AM) radio transmission around 1900. While working to develop AM transmitte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 evo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Guglielmo Marconi
Guglielmo Giovanni Maria Marconi, 1st Marquis of Marconi (; 25 April 187420 July 1937) was an Italian inventor and electrical engineer, known for his creation of a practical radio wave-based wireless telegraph system. This led to Marconi being 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".Guglielmo Marconi: The Nobel Prize in Physics 1909 . nobelprize.org Marconi was also an entrepreneur, businessman, and founder of The Wireless Telegraph & Signal Company in the |
Metal Filings
Iron filings are very small pieces of iron that look like a light powder. As the name suggests, iron filings were traditionally obtained from metal working operations as the scrap material filed off larger iron and steel parts. They are very often used in science demonstrations to show the direction of a magnetic field. Since iron is a ferromagnetic material, a magnetic field induces each particle to become a tiny bar magnet. The south pole of each particle then attracts the north poles of its neighbors, and this process is repeated over a wide area creates chains of filings parallel to the direction of the magnetic field. Iron Filings are used in many places, including schools where they test the reaction of the filings to magnets. They are also used in some toys, most famously Wooly Willy, where they serve to mimic hair on a cartoon face. See also *Coherer The coherer was a primitive form of radio signal detector used in the first radio receivers during the wireless te ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Frequency
Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around to around . This is roughly between the upper limit of audio frequencies and the lower limit of infrared frequencies; these are the frequencies at which energy from an oscillating current can radiate off a conductor into space as radio waves. Different sources specify different upper and lower bounds for the frequency range. Electric current Electric currents that oscillate at radio frequencies (RF currents) have special properties not shared by direct current or lower audio frequency alternating current, such as the 50 or 60 Hz current used in electrical power distribution. * Energy from RF currents in conductors can radiate into space as electromagnetic waves ( radio waves). This is the basis of radio technology. * RF current does not penetrate deeply into ele ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monterubbiano
Monterubbiano is a town and ''comune'' in the Province of Fermo, in the Marche region of Italy. It is on a hill from the Adriatic Sea. History In pre-historic times the area was inhabited by the Piceni (9th-3rd centuries BC). After the Roman conquest, it received the status of ''urbs urbana'' (built city) in 268 BC. In the 5th century it was captured by the Visigoths. In the 12th century, it was a free commune, thwarting the attempts from Fermo to capture it. In the 15th century it was acquired by Francesco Sforza, who fortified it; in 1663 it became part of the Papal States, to which (apart the Napoleonic period) it remained until 1860, when it was annexed to the newly formed Kingdom of Italy. The Italian Branch of Sabbath Rest Advent Church can claim that the number of members is estimated at more than 2000 members, with its headquarter in Monterubbiano, but with the presence in many other Italian places. Main sights *''Mura Castellane'' (walls), built by Francesco Sforza in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alexander Popov (physicist)
Alexander Stepanovich Popov (sometimes spelled Popoff; russian: Алекса́ндр Степа́нович Попо́в; – ) was a Russian physicist, who was one of the first persons to invent a radio receiving device. declassified 8 January 2008 Popov's work as a teacher at a Russian naval school led him to explore high frequency electrical phenomena. On 7 May 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 24 March 1896 demonstration, he transmitted radio signals 250 meters 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. Early life Born in the town of Krasnoturinsk, Sverdlovsk Oblast in the Urals as the son of a priest, he became interested in natural sciences when he was a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oliver 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's 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. Lodge was also noted for his Spiritualist beliefs and pseudoscientifc research into life after death, a topic on which he wrote many books, including the best-selling ''Raymond; or, Life and Death'' (1916), describing what he believed to be detailed messages through a medium from his deceased adult son who was killed in World War I. Life Oliver Lodge was born in 1851 at 'The Views', Penkhull, then a rural village hig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
