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Magnetron
The CAVITY MAGNETRON is a high-powered vacuum tube that generates microwaves using the interaction of a stream of electrons with a magnetic field while moving past a series of open metal cavities (cavity resonators ). Electrons pass by the openings to these cavities and cause radio waves to oscillate within, similar to the way a whistle produces a tone when excited by an air stream blown past its opening. The frequency of the microwaves produced, the resonant frequency , is determined by the cavities' physical dimensions. Unlike other vacuum tubes such as a klystron or a traveling-wave tube (TWT), the magnetron cannot function as an amplifier in order to increase the intensity of an applied microwave signal; the magnetron serves solely as an oscillator , generating a microwave signal from direct current electricity supplied to the vacuum tube. An early form of magnetron was invented by H. Gerdien in 1910. Another form of magnetron tube, the split-anode magnetron, was invented by Albert Hull
Albert Hull
in 1920, but it wasn't capable of high frequencies and was of little use. Similar devices were experimented with by many teams through the 1920s and 1930s
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Megatron
MEGATRON is a character from the Transformers franchise, created by Hasbro in 1984, based on a toy design by Takara . The original Megatron
Megatron
was the Decepticon Leader, which could transform into three different types of guns; a Walther P38 handgun , a particle beam cannon , and a telescopic laser cannon . He is a sentient robotic lifeform from the planet Cybertron and the leader of the villainous Decepticons as well as the archenemy of the Autobot leader Optimus Prime . Megatron
Megatron
is usually depicted as having risen up from the lowly worker to become a champion in gladiatorial combat . As a gladiator, he took the legendary name "Megatronus " as his own and would similarly inspire a later villainous character . He called for an end to his planet Cybertron's corrupted governing body and told the downtrodden that freedom of self-determination was the right of all sentient beings, becoming a mentor to the young Optimus Prime. Prime would later use his teachings against him when he became corrupt. He has the ability to transform between his robot shape and various weapons or vehicles, but these "alternate-modes", his origins and even personality, can vary depending on which "universe" he's seen in. This origin is considered the most consistent between the various incarnations
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Metatron
METATRON (Hebrew מטטרון; prob. derived from the Latin mētātor: "one who metes out or marks off a place, a divider and fixer of boundaries", "a measurer", although several other suggestions exist ) or MATTATRON is an archangel in Judaism
Judaism
and known in Judaism
Judaism
as the Recording Angel
Angel
or the Chancellor of Heaven (which makes Adramelech his infernal counterpart). The name Metatron is not mentioned in the Hebrew Bible, nor is it mentioned in the early Enoch literature. How the name originated is a matter of debate. Although Metatron is mentioned in a few brief passages in the Talmud
Talmud
, he appears primarily in mystical Kabbalistic texts within the Rabbinic literature . In that tradition, he is the highest of the angels and serves as the celestial scribe or "recording angel". According to Jewish apocrypha , Metatron is the name Enoch received, after his transformation into an angel
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Alnico
ALNICO is an acronym referring to a family of iron alloys which in addition to iron are composed primarily of aluminium (Al), nickel (Ni) and cobalt (Co), hence al-ni-co. They also include copper , and sometimes titanium . Alnico alloys are ferromagnetic , with a high coercivity (resistance to loss of magnetism) and are used to make permanent magnets . Before the development of rare-earth magnets in the 1970s, they were the strongest type of permanent magnet. Other trade names for alloys in this family are: Alni, Alcomax, Hycomax, Columax, and Ticonal. The composition of alnico alloys is typically 8–12% Al, 15–26% Ni, 5–24% Co, up to 6% Cu, up to 1% Ti, and the balance is Fe. The development of alnico began in 1931, when T. Mishima in Japan discovered that an alloy of iron, nickel, and aluminum had a coercivity of 400 oersteds (Oe; 0.07957 kA/m), double that of the best magnet steels of the time. Assortment of alnico horseshoe magnets, 1956 CONTENTS * 1 Properties * 2 Classification * 3 Manufacturing process * 4 Uses * 5 References * 6 Further reading PROPERTIES Assortment of Alnico magnets in 1956. Alnico 5, developed during World War 2, led to a new generation of compact permanent magnet motors and loudspeakers. Alnico 5 magnet used in a magnetron tube in an early microwave oven. About 3 in (8 cm) long
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Rare Earth Magnet
RARE-EARTH MAGNETS are strong permanent magnets made from alloys of rare-earth elements (elements in the lanthanide series, plus scandium and yttrium ). Developed in the 1970s and 1980s, rare-earth magnets are the strongest type of permanent magnets made, producing significantly stronger magnetic fields than other types such as ferrite or alnico magnets. The magnetic field typically produced by rare-earth magnets can exceed 1.4 teslas , whereas ferrite or ceramic magnets typically exhibit fields of 0.5 to 1 tesla. There are two types: neodymium magnets and samarium-cobalt magnets . Magnetostrictive rare-earth magnets such as Terfenol-D also have applications, e.g. in loudspeakers . Rare-earth magnets are extremely brittle and also vulnerable to corrosion , so they are usually plated or coated to protect them from breaking, chipping, or crumbling into powder. The term "rare earth" can be misleading, as these metals are not particularly rare or precious; they are about as abundant as tin or lead. The development of rare-earth magnets began around 1966, when K. J. Strnat and G. Hoffer of the US Air Force Materials Laboratory discovered that an alloy of yttrium and cobalt , YCo5, had by far the largest magnetic anisotropy constant of any material then known. Neodymium
Neodymium
magnets (small cylinders) lifting steel balls. As shown here, rare-earth magnets can easily lift thousands of times their own weight
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Vacuum Tube
In electronics , a VACUUM TUBE, an ELECTRON TUBE, or just a TUBE (North America), or VALVE (Britain and some other regions), is a device that controls electric current between electrodes in an evacuated container. Vacuum
Vacuum
tubes mostly rely on thermionic emission of electrons from a hot filament or a cathode heated by the filament. This type is called a THERMIONIC TUBE or THERMIONIC VALVE. A phototube , however, achieves electron emission through the photoelectric effect . Not all electronic circuit valves/electron tubes are vacuum tubes (evacuated); gas-filled tubes are similar devices containing a gas, typically at low pressure, which exploit phenomena related to electric discharge in gases , usually without a heater. The simplest vacuum tube, the diode , contains only a heater, a heated electron-emitting cathode (the filament itself acts as the cathode in some diodes), and a plate (anode). Current can only flow in one direction through the device between the two electrodes, as electrons emitted by the cathode travel through the tube and are collected by the anode. Adding one or more control grids within the tube allows the current between the cathode and anode to be controlled by the voltage on the grid or grids. Tubes with grids can be used for many purposes, including amplification , rectification , switching , oscillation , and display
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Microwave
MICROWAVES are a form of electromagnetic radiation with wavelengths ranging from one meter to one millimeter; with frequencies between 300 MHz (100 cm) and 300 GHz (0.1 cm). Different sources define different frequency ranges as microwaves; the above broad definition includes both UHF and EHF (millimeter wave ) bands. A more common definition in radio engineering is the range between 1 and 100 GHz (300 and 3 mm). In all cases, microwaves include the entire SHF band (3 to 30 GHz, or 10 to 1 cm) at minimum. Frequencies in the microwave range are often referred to by their IEEE radar band designations: S , C , X , Ku , K , or Ka band , or by similar NATO or EU designations. The prefix _micro-_ in _microwave_ is not meant to suggest a wavelength in the micrometer range. It indicates that microwaves are "small", compared to the radio waves used prior to microwave technology, in that they have shorter wavelengths. The boundaries between far infrared , terahertz radiation , microwaves, and ultra-high-frequency radio waves are fairly arbitrary and are used variously between different fields of study. Microwaves travel by line-of-sight ; unlike lower frequency radio waves they do not diffract around hills, follow the earth's surface as ground waves , or reflect from the ionosphere , so terrestrial microwave communication links are limited by the visual horizon to about 40 miles (64 km)
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Electron
The ELECTRON is a subatomic particle , symbol e− or β− , with a negative elementary electric charge . Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no known components or substructure. The electron has a mass that is approximately 1/1836 that of the proton . Quantum mechanical properties of the electron include an intrinsic angular momentum (spin ) of a half-integer value, expressed in units of the reduced Planck constant , _ħ_. As it is a fermion , no two electrons can occupy the same quantum state , in accordance with the Pauli exclusion principle . Like all elementary particles, electrons exhibit properties of both particles and waves : they can collide with other particles and can be diffracted like light. The wave properties of electrons are easier to observe with experiments than those of other particles like neutrons and protons because electrons have a lower mass and hence a longer De Broglie wavelength for a given energy. Electrons play an essential role in numerous physical phenomena, such as electricity , magnetism , and thermal conductivity , and they also participate in gravitational , electromagnetic and weak interactions . Since an electron has charge, it has a surrounding electric field , and if that electron is moving relative to an observer it will generate a magnetic field
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Magnetic Field
A MAGNETIC FIELD is the magnetic effect of electric currents and magnetic materials . The magnetic field at any given point is specified by both a _direction_ and a _magnitude_ (or strength); as such it is represented by a vector field . The term is used for two distinct but closely related fields denoted by the symbols B and H, where H is measured in units of amperes per meter (symbol: A⋅m−1 or A/m) in the SI . B is measured in teslas (symbol: T) and newtons per meter per ampere (symbol: N⋅m−1⋅A−1 or N/(m⋅A)) in the SI . B is most commonly defined in terms of the Lorentz force it exerts on moving electric charges. Magnetic fields can be produced by moving electric charges and the intrinsic magnetic moments of elementary particles associated with a fundamental quantum property , their spin . In special relativity , electric and magnetic fields are two interrelated aspects of a single object, called the electromagnetic tensor ; the split of this tensor into electric and magnetic fields depends on the relative velocity of the observer and charge. In quantum physics , the electromagnetic field is quantized and electromagnetic interactions result from the exchange of photons . In everyday life, magnetic fields are most often encountered as a force created by permanent magnets , which pull on ferromagnetic materials such as iron, cobalt, or nickel, and attract or repel other magnets
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Cavity Resonator
A RESONATOR is a device or system that exhibits resonance or resonant behavior, that is, it naturally oscillates at some frequencies , called its resonant frequencies , with greater amplitude than at others. The oscillations in a resonator can be either electromagnetic or mechanical (including acoustic ). Resonators are used to either generate waves of specific frequencies or to select specific frequencies from a signal. Musical instruments use acoustic resonators that produce sound waves of specific tones. Another example is quartz crystals used in electronic devices such as radio transmitters and quartz watches to produce oscillations of very precise frequency. A CAVITY RESONATOR is one in which waves exist in a hollow space inside the device. In electronics and radio, microwave cavities consisting of hollow metal boxes are used in microwave transmitters, receivers and test equipment to control frequency, in place of the tuned circuits which are used at lower frequencies. Acoustic cavity resonators, in which sound is produced by air vibrating in a cavity with one opening, are known as Helmholtz resonators
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Frequency
FREQUENCY is the number of occurrences of a repeating event per unit time . It is also referred to as TEMPORAL FREQUENCY, which emphasizes the contrast to spatial frequency and angular frequency . The PERIOD is the duration of time of one cycle in a repeating event, so the period is the reciprocal of the frequency. For example, if a newborn baby's heart beats at a frequency of 120 times a minute, its period—the time interval between beats—is half a second (that is, 60 seconds divided by 120 beats ). Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio (sound ) signals, radio waves , and light . CONTENTS * 1 Definitions * 2 Units * 3 Period versus frequency * 4 Related types of frequency * 5 In wave propagation * 6 Measurement * 6.1 Counting * 6.2 Stroboscope * 6.3 Frequency counter * 6.4 Heterodyne methods * 7 Examples * 7.1 Light * 7.2 Sound * 7.3 Line current * 8 See also * 9 Notes and references * 10 Further reading * 11 External links DEFINITIONS As time elapses—here moving left to right on the horizontal axis—the five sinusoidal waves vary, or cycle, regularly at different rates
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Resonant Frequency
In physics , RESONANCE is a phenomenon in which a vibrating system or external force drives another system to oscillate with greater amplitude at specific frequencies . Frequencies at which the response amplitude is a relative maximum are known as the system's RESONANT FREQUENCIES or RESONANCE FREQUENCIES. At resonant frequencies, small periodic driving forces have the ability to produce large amplitude oscillations, due to the storage of vibrational energy . CONTENTS * 1 Overview * 2 Examples * 2.1 Swing * 2.2 Mechanical and acoustic resonance * 2.2.1 Tacoma Narrows Bridge * 2.3 Electrical resonance * 2.4 Optical resonance * 2.5 Orbital resonance * 2.6 Schumann resonance * 2.7 Atomic, particle, and molecular resonance * 2.8 International Space Station * 2.9 Other examples * 3 Theory * 4 Resonators * 5 _Q_ factor * 6 See also * 7 References * 8 External links OVERVIEW Resonance occurs when a system is able to store and easily transfer energy between two or more different storage modes (such as kinetic energy and potential energy in the case of a simple pendulum). However, there are some losses from cycle to cycle, called damping . When damping is small, the resonant frequency is approximately equal to the natural frequency of the system, which is a frequency of unforced vibrations. Some systems have multiple, distinct, resonant frequencies
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Klystron
A KLYSTRON is a specialized linear-beam vacuum tube , invented in 1937 by American electrical engineers Russell and Sigurd Varian , which is used as an amplifier for high radio frequencies , from UHF up into the microwave range. Low-power klystrons are used as oscillators in terrestrial microwave relay communications links, while high-power klystrons are used as output tubes in UHF television transmitters , satellite communication , and radar transmitters , and to generate the drive power for modern particle accelerators . In a klystron, an electron beam interacts with radio waves as it passes through resonant cavities , metal boxes along the length of a tube. The electron beam first passes through a cavity to which the input signal is applied. The energy of the electron beam amplifies the signal, and the amplified signal is taken from a cavity at the other end of the tube. The output signal can be coupled back into the input cavity to make an electronic oscillator to generate radio waves. The gain of klystrons can be high, 60 dB (one million) or more, with output power up to tens of megawatts , but the bandwidth is narrow, usually a few percent although it can be up to 10% in some devices. A reflex klystron is an obsolete type in which the electron beam was reflected back along its path by a high potential electrode, used as an oscillator
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Traveling-wave Tube
A TRAVELING-WAVE TUBE (TWT, pronounced "twit") or TRAVELING-WAVE TUBE AMPLIFIER (TWTA, pronounced "tweeta") is a specialized vacuum tube that is used in electronics to amplify radio frequency (RF) signals in the microwave range. The TWT belongs to a category of "linear beam" tubes, such as the klystron , in which the radio wave is amplified by absorbing power from a beam of electrons as it passes down the tube. Although there are various types of TWT, two major categories are: * Helix
Helix
TWT - in which the radio waves interact with the electron beam while traveling down a wire helix which surrounds the beam. These have wide bandwidth, but output power is limited to a few hundred watts. * Coupled cavity TWT - in which the radio wave interacts with the beam in a series of cavity resonators through which the beam passes. These function as narrowband power amplifiers.A major advantage of the TWT over some other microwave tubes is its ability to amplify a wide range of frequencies , a wide bandwidth . The bandwidth of the helix TWT can be as high as two octaves , while the cavity versions have bandwidths of 10–20%. Operating frequencies range from 300 MHz to 50 GHz. The power gain of the tube is on the order of 40 to 70 decibels , and output power ranges from a few watts to megawatts . TWTs account for over 50% of the sales volume of all microwave vacuum tubes
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Amplifier
An AMPLIFIER, ELECTRONIC AMPLIFIER or (informally) AMP is an electronic device that can increase the power of a signal (a time-varying voltage or current ). An amplifier uses electric power from a power supply to increase the amplitude of a signal. The amount of amplification provided by an amplifier is measured by its gain : the ratio of output to input. An amplifier is a circuit that can give a power gain greater than one. An amplifier can either be a separate piece of equipment or an electrical circuit contained within another device. Amplification is fundamental to modern electronics, and amplifiers are widely used in almost all electronic equipment. Amplifiers can be categorized in different ways. One is by the frequency of the electronic signal being amplified; audio amplifiers amplify signals in the audio (sound) range of less than 20 kHz, RF amplifiers amplify frequencies in the radio frequency range between 20 kHz and 300 GHz, and servo amplifiers and instrumentation amplifiers may work with very low frequencies down to direct current. A further distinction is whether the output is a linear or nonlinear representation of the input. Amplifiers can also be categorized by their physical placement in the signal chain ; a preamplifier may precede other signal processing stages, for example. The first practical device that could amplify was the triode vacuum tube , invented in 1906 by Lee De Forest , which led to the first amplifiers around 1912
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Electronic Oscillator
An ELECTRONIC OSCILLATOR is an electronic circuit that produces a periodic, oscillating electronic signal, often a sine wave or a square wave . Oscillators convert direct current (DC) from a power supply to an alternating current (AC) signal. They are widely used in many electronic devices. Common examples of signals generated by oscillators include signals broadcast by radio and television transmitters , clock signals that regulate computers and quartz clocks , and the sounds produced by electronic beepers and video games . Oscillators are often characterized by the frequency of their output signal: * A low-frequency oscillator (LFO) is an electronic oscillator that generates a frequency below approximately 20 Hz. This term is typically used in the field of audio synthesizers , to distinguish it from an audio frequency oscillator. * An audio oscillator produces frequencies in the audio range, about 16 Hz to 20 kHz. * An RF oscillator produces signals in the radio frequency (RF) range of about 100 kHz to 100 GHz. Oscillators designed to produce a high-power AC output from a DC supply are usually called inverters . There are two main types of electronic oscillator — the linear or harmonic oscillator and the nonlinear or relaxation oscillator . 1 MHz electronic oscillator circuit which uses the resonant properties of an internal quartz crystal to control the frequency. Provides the clock signal for digital devices such as computers
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