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Foxhole Radio
A foxhole radio is a makeshift radio that was built by soldiers in World War II for entertainment, to listen to local radio stations using amplitude modulation. They were first reported at the Battle of Anzio, Italy, spreading later across the European and Pacific theaters. The foxhole radio was a crude crystal radio which used a safety razor blade as a radio wave detector with the blade acting as the crystal, and a wire, safety pin, or, later, a graphite pencil lead serving as the cat's whisker. The foxhole radio, like a mineral crystal radio receiver, had no power source and ran off the power received from the radio station. They were named, likely by the press, for the foxhole, a defensive fighting position used during the war. There are also accounts of prisoners of war in World War II and in the Vietnam War having constructed foxhole radios. History The maker of the first foxhole radio is unknown, but it was almost certainly invented by a soldier stationed at the An ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anzio Beachhead
The Battle of Anzio was a battle of the Italian Campaign of World War II that took place from January 22, 1944 (beginning with the Allied amphibious landing known as Operation Shingle) to June 5, 1944 (ending with the capture of Rome). The operation was opposed by German forces in the area of Anzio and Nettuno. The operation was initially commanded by Major General John P. Lucas, of the U.S. Army, commanding U.S. VI Corps with the intent to outflank German forces at the Winter Line and enable an attack on Rome. The success of an amphibious landing at that location, in a basin consisting substantially of reclaimed marshland and surrounded by mountains, depended on the element of surprise and the swiftness with which the invaders could build up strength and move inland relative to the reaction time and strength of the defenders. Any delay could result in the occupation of the mountains by the defenders and the consequent entrapment of the invaders. Lieutenant General Mark W. Cl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Foxhole Radio Circuits
Foxhole may refer to: * Foxhole, a type of defensive fighting position constructed in a military context * Foxholes, Hertford, an eastern suburb of Hertford * Foxholes, North Yorkshire, a village and civil parish in Northern England * Foxhole, Cornwall, a village in mid Cornwall * Foxhole, Scotland, a hamlet in the Scottish Highlands * Foxhole (band), a post-rock band from Bowling Green, America * ''Foxhole'' (video game), a sandbox massively multiplayer online game See also * '' Foxhole in Cairo'', a 1960 British war film * ''Foxhole'' (film), a 2021 American war film * Foxhole radio A foxhole radio is a makeshift radio that was built by soldiers in World War II for entertainment, to listen to local radio stations using amplitude modulation. They were first reported at the Battle of Anzio, Italy, spreading later across the ..., a radio built by G.I.s during World War II * Foxhole Heath, an area of a heathland near the village of Eriswell in Suffolk * '' Dugout to Fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carrier Wave
In telecommunications, a carrier wave, carrier signal, or just carrier, is a waveform (usually sinusoidal) that is modulated (modified) with an information-bearing signal for the purpose of conveying information. This carrier wave usually has a much higher frequency than the input signal does. The purpose of the carrier is usually either to transmit the information through space as an electromagnetic wave (as in radio communication), or to allow several carriers at different frequencies to share a common physical transmission medium by frequency division multiplexing (as in a cable television system). The term originated in radio communication, where the carrier wave creates the waves which carry the information (modulation) through the air from the transmitter to the receiver. The term is also used for an unmodulated emission in the absence of any modulating signal. In music production, carrier signals can be controlled by a modulating signal to change the sound property of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrical Impedance
In electrical engineering, impedance is the opposition to alternating current presented by the combined effect of resistance and reactance in a circuit. Quantitatively, the impedance of a two-terminal circuit element is the ratio of the complex representation of the sinusoidal voltage between its terminals, to the complex representation of the current flowing through it. In general, it depends upon the frequency of the sinusoidal voltage. Impedance extends the concept of resistance to alternating current (AC) circuits, and possesses both magnitude and phase, unlike resistance, which has only magnitude. Impedance can be represented as a complex number, with the same units as resistance, for which the SI unit is the ohm (). Its symbol is usually , and it may be represented by writing its magnitude and phase in the polar form . However, Cartesian complex number representation is often more powerful for circuit analysis purposes. The notion of impedance is useful for perf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Resonant Frequency
Resonance describes the phenomenon of increased amplitude that occurs when the frequency of an applied periodic force (or a Fourier component of it) is equal or close to a natural frequency of the system on which it acts. When an oscillating force is applied at a resonant frequency of a dynamic system, the system will oscillate at a higher amplitude than when the same force is applied at other, non-resonant frequencies. Frequencies at which the response amplitude is a relative maximum are also known as resonant frequencies or resonance frequencies of the system. Small periodic forces that are near a resonant frequency of the system have the ability to produce large amplitude oscillations in the system due to the storage of vibrational energy. Resonance phenomena occur with all types of vibrations or waves: there is mechanical resonance, orbital resonance, acoustic resonance, electromagnetic resonance, nuclear magnetic resonance (NMR), electron spin resonance (ESR) and reson ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inductance
Inductance is the tendency of an electrical conductor to oppose a change in the electric current flowing through it. The flow of electric current creates a magnetic field around the conductor. The field strength depends on the magnitude of the current, and follows any changes in current. From Faraday's law of induction, any change in magnetic field through a circuit induces an electromotive force (EMF) (voltage) in the conductors, a process known as electromagnetic induction. This induced voltage created by the changing current has the effect of opposing the change in current. This is stated by Lenz's law, and the voltage is called ''back EMF''. Inductance is defined as the ratio of the induced voltage to the rate of change of current causing it. It is a proportionality factor that depends on the geometry of circuit conductors and the magnetic permeability of nearby materials. An electronic component designed to add inductance to a circuit is called an inductor. It typically ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Resonant Circuit
An LC circuit, also called a resonant circuit, tank circuit, or tuned circuit, is an electric circuit consisting of an inductor, represented by the letter L, and a capacitor, represented by the letter C, connected together. The circuit can act as an electrical resonator, an electrical analogue of a tuning fork, storing energy oscillating at the circuit's resonant frequency. LC circuits are used either for generating signals at a particular frequency, or picking out a signal at a particular frequency from a more complex signal; this function is called a bandpass filter. They are key components in many electronic devices, particularly radio equipment, used in circuits such as oscillators, filters, tuners and frequency mixers. An LC circuit is an idealized model since it assumes there is no dissipation of energy due to resistance. Any practical implementation of an LC circuit will always include loss resulting from small but non-zero resistance within the components and connec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parasitic Capacitance
Parasitic capacitance is an unavoidable and usually unwanted capacitance that exists between the parts of an electronic component or circuit simply because of their proximity to each other. When two electrical conductors at different voltages are close together, the electric field between them causes electric charge to be stored on them; this effect is capacitance. All practical circuit elements such as inductors, diodes, and transistors have internal capacitance, which can cause their behavior to depart from that of ideal circuit elements. Additionally, there is always non-zero capacitance between any two conductors; this can be significant with closely spaced conductors, such as wires or printed circuit board traces. The parasitic capacitance between the turns of an inductor or other wound component is often described as ''self-capacitance''. However, in electromagnetics, the term self-capacitance more correctly refers to a different phenomenon: the capacitance of a condu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
David Edward Hughes
David Edward Hughes (16 May 1830 – 22 January 1900), was a British-American inventor, practical experimenter, and professor of music known for his work on the printing telegraph and the microphone. He is generally considered to have been born in London but his family moved around that time so he may have been born in Corwen, Wales. His family moved to the U.S. while he was a child and he became a professor of music in Kentucky. In 1855 he patented a printing telegraph. He moved back to London in 1857 and further pursued experimentation and invention, coming up with an improved carbon microphone in 1878. In 1879 he identified what seemed to be a new phenomenon during his experiments: sparking in one device could be heard in a separate portable microphone apparatus he had set up. It was most probably radio transmissions but this was nine years before electromagnetic radiation was a proven concept and Hughes was convinced by others that his discovery was simply electroma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Schottky Diode
The Schottky diode (named after the German physicist Walter H. Schottky), also known as Schottky barrier diode or hot-carrier diode, is a semiconductor diode formed by the junction of a semiconductor with a metal. It has a low forward voltage drop and a very fast switching action. The cat's-whisker detectors used in the early days of wireless and metal rectifiers used in early power applications can be considered primitive Schottky diodes. When sufficient forward voltage is applied, a current flows in the forward direction. A silicon p–n diode has a typical forward voltage of 600–700 mV, while the Schottky's forward voltage is 150–450 mV. This lower forward voltage requirement allows higher switching speeds and better system efficiency. History Walter H. Schottky (1886–1976) in 1914, discovered an irregularity in the emission of thermions in a vacuum tube, now known as the Schottky effect. Construction A metal–semiconductor junction is formed between a metal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Semiconductor
A semiconductor is a material which has an electrical resistivity and conductivity, electrical conductivity value falling between that of a electrical conductor, conductor, such as copper, and an insulator (electricity), insulator, such as glass. Its electrical resistivity and conductivity, resistivity falls as its temperature rises; metals behave in the opposite way. Its conducting properties may be altered in useful ways by introducing impurities ("doping (semiconductor), doping") into the crystal structure. When two differently doped regions exist in the same crystal, a semiconductor junction is created. The behavior of charge carriers, which include electrons, ions, and electron holes, at these junctions is the basis of diodes, transistors, and most modern electronics. Some examples of semiconductors are silicon, germanium, gallium arsenide, and elements near the so-called "metalloid staircase" on the periodic table. After silicon, gallium arsenide is the second-most common s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rectifier
A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction. The reverse operation (converting DC to AC) is performed by an Power inverter, inverter. The process is known as ''rectification'', since it "straightens" the direction of current. Physically, rectifiers take a number of forms, including Vacuum tube#Diodes, vacuum tube diodes, wet chemical cells, mercury-arc valves, stacks of copper and selenium rectifier, selenium oxide plates, Diode#Semiconductor diodes, semiconductor diodes, silicon-controlled rectifiers and other silicon-based semiconductor switches. Historically, even synchronous electromechanical switches and motor-generator sets have been used. Early radio receivers, called crystal radios, used a "Cat's-whisker detector, cat's whisker" of fine wire pressing on a crystal of galena (lead sulfide) to serve as a point-contact rectifier or "crystal detec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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