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Dip Meter
:''"Dip meter" can also refer to an influential early commercial expert system called Dipmeter Advisor; or may refer to an instrument that measures the magnetic dip angle of Earth's magnetic field, the field line angle in a vertical plane.'' Grid dip oscillator (GDO), also called grid dip meter, gate dip meter, dip meter, or just dipper, is a type of electronic instrument that measures the resonant frequency of nearby unconnected radio frequency tuned circuits. It is a variable-frequency oscillator that circulates a small-amplitude signal through an exposed coil, whose electromagnetic field can interact with adjacent circuitry. The oscillator loses power when its coil is near a circuit that resonates at the same frequency. A meter on the GDO registers the amplitude drop, or "dip", hence the name. Dip oscillators have been widely used by amateur radio operators for measuring the properties of resonant circuits, filters, and antennas. They can also be used for transmission line tes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Expert System
In artificial intelligence, an expert system is a computer system emulating the decision-making ability of a human expert. Expert systems are designed to solve complex problems by reasoning through bodies of knowledge, represented mainly as if–then rules rather than through conventional procedural code. The first expert systems were created in the 1970s and then proliferated in the 1980s. Expert systems were among the first truly successful forms of artificial intelligence (AI) software. An expert system is divided into two subsystems: the inference engine and the knowledge base. The knowledge base represents facts and rules. The inference engine applies the rules to the known facts to deduce new facts. Inference engines can also include explanation and debugging abilities. History Early development Soon after the dawn of modern computers in the late 1940s and early 1950s, researchers started realizing the immense potential these machines had for modern society. One of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vacuum Tube
A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric voltage, potential difference has been applied. The type known as a thermionic tube or thermionic valve utilizes thermionic emission of electrons from a hot cathode for fundamental electronic functions such as signal amplifier, amplification and current rectifier, rectification. Non-thermionic types such as a vacuum phototube, however, achieve electron emission through the photoelectric effect, and are used for such purposes as the detection of light intensities. In both types, the electrons are accelerated from the cathode to the anode by the electric field in the tube. The simplest vacuum tube, the diode (i.e. Fleming valve), invented in 1904 by John Ambrose Fleming, contains only a heated electron-emitting cathode and an anode. Electrons can only flow in one direction through the device—fro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Variable-frequency Oscillator
A variable frequency oscillator (VFO) in electronics is an oscillator whose frequency can be tuned (i.e., varied) over some range. It is a necessary component in any tunable radio transmitter or receiver that works by the superheterodyne principle, and controls the radio frequency, frequency to which the apparatus is tuned. Purpose In a simple superheterodyne receiver, the incoming radio frequency signal (at frequency f_) from the antenna (radio), antenna is frequency mixer, ''mixed'' with the VFO output signal tuned to f_, producing an intermediate frequency (IF) signal that can be processed downstream to extract the modulation, modulated information. Depending on the receiver design, the IF signal frequency is chosen to be either the sum of the two frequencies at the mixer inputs (Heterodyne#Up and down converters, up-conversion), f_+f_ or more commonly, the difference frequency (down-conversion), f_-f_. In addition to the desired ''IF'' signal and its unwanted image (the mixin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Field Strength Meter
In telecommunications, a field strength meter is an instrument that measures the electric field strength emanating from a transmitter. The relation between the electric field and the transmitted power In ideal free space, the electric field strength produced by a transmitter with an isotropic radiator is readily calculated. : \mbox \approx \frac where : \mbox is the electric field strength in volts per meter : P is the transmitter power output in watts : d is the distance from the radiator in meters The factor \sqrt is an approximation of \sqrt where Z_0=376.730 313 668(57) \Omega\quadis the impedance of free space. \Omega is the symbol for ohms. It is clear that electric field strength is inversely proportional to the distance between the transmitter and the receiver. However, this relation is impractical for calculating the field strength produced by terrestrial transmitters, where reflections and attenuation caused by objects around the transmitte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antenna Analyzer
An antenna analyzer or in British aerial analyser (also known as a noise bridge, RX bridge, SWR analyzer, or RF analyzer) is a device used for measuring the input impedance of antenna systems in radio electronics applications. In radio communications systems, including amateur radio, an antenna analyzer is a common tool used for fine tuning antenna and feedline performance, as well as troubleshooting them. Antenna bridges have long been used in the broadcast industry to tune antennas. A bridge is available which measures complex impedance while the transmitter is operating, practically a necessity when tuning multi-tower antenna systems. In more recent times the direct-reading network analyzers have become more common. Types of analysers There are several different instruments of varying complexity and accuracy for testing antennas and their feed lines. All can also be used to measure other electrical circuits and components (at least, in principle). * The simplest is an SWR me ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Absorption Wavemeter
An absorption wavemeter is a simple electronic instrument used to measure the frequency of radio waves. It is an older method of measuring frequency, widely used from the birth of radio in the early 20th century until the 1970s, when the development of inexpensive frequency counters, which have far greater accuracy, made it largely obsolete. A wavemeter consists of an adjustable resonant circuit calibrated in frequency, with a meter or other means to measure the voltage or current in the circuit. When adjusted to resonance with the unknown frequency, the resonant circuit absorbs energy, which is indicated by a dip on the meter. Then the frequency can be read from the dial. Wavemeters are used for frequency measurements that do not require high accuracy, such as checking that a radio transmitter is operating within its correct frequency band, or checking for harmonics in the output. Many radio amateurs keep them as a simple way to check their output frequency. Similar devices ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Field Strength Meter
In telecommunications, a field strength meter is an instrument that measures the electric field strength emanating from a transmitter. The relation between the electric field and the transmitted power In ideal free space, the electric field strength produced by a transmitter with an isotropic radiator is readily calculated. : \mbox \approx \frac where : \mbox is the electric field strength in volts per meter : P is the transmitter power output in watts : d is the distance from the radiator in meters The factor \sqrt is an approximation of \sqrt where Z_0=376.730 313 668(57) \Omega\quadis the impedance of free space. \Omega is the symbol for ohms. It is clear that electric field strength is inversely proportional to the distance between the transmitter and the receiver. However, this relation is impractical for calculating the field strength produced by terrestrial transmitters, where reflections and attenuation caused by objects around the transmitte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrical Overload
In an electric power system, overcurrent or excess current is a situation where a larger than intended electric current exists through a conductor, leading to excessive generation of heat, and the risk of fire or damage to equipment. Possible causes for overcurrent include short circuits, excessive load, incorrect design, an arc fault, or a ground fault. Fuses, circuit breakers, and current limiters are commonly used overcurrent protection (OCP) mechanisms to control the risks. Circuit breakers, relays, and fuses protect circuit wiring from damage caused by overcurrent. Related standards *IEC 60364-4-43: Electrical installations of buildings – Part 4-43: Protection for safety – Protection against overcurrent See also * Current limiting * Electrical fault * Electrical safety * Overvoltage When the voltage in a circuit or part of it is raised above its upper design limit, this is known as overvoltage. The conditions may be hazardous. Depending on its duration, the overvo ... [...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] |
LC 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 conn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heathkit GD-1B Grid Dip Meters
Heathkit is the brand name of kits and other electronic products produced and marketed by the Heath Company. The products over the decades have included electronic test equipment, high fidelity home audio equipment, television receivers, amateur radio equipment, robots, electronic ignition conversion modules for early model cars with point style ignitions, and the influential Heath H-8, H-89, and H-11 hobbyist computers, which were sold in kit form for assembly by the purchaser. Heathkit manufactured electronic kits from 1947 until 1992. After closing that business, the Heath Company continued with its products for education, and motion-sensor lighting controls. The lighting control business was sold around 2000. The company announced in 2011 that they were reentering the kit business after a 20-year hiatus but then filed for bankruptcy in 2012,Swindwa, Julie"Disassembly complete: Heathkit is no more" ''The Herald-Palladium'', 19 July 2012 and under new ownership began restr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antenna Analyzer
An antenna analyzer or in British aerial analyser (also known as a noise bridge, RX bridge, SWR analyzer, or RF analyzer) is a device used for measuring the input impedance of antenna systems in radio electronics applications. In radio communications systems, including amateur radio, an antenna analyzer is a common tool used for fine tuning antenna and feedline performance, as well as troubleshooting them. Antenna bridges have long been used in the broadcast industry to tune antennas. A bridge is available which measures complex impedance while the transmitter is operating, practically a necessity when tuning multi-tower antenna systems. In more recent times the direct-reading network analyzers have become more common. Types of analysers There are several different instruments of varying complexity and accuracy for testing antennas and their feed lines. All can also be used to measure other electrical circuits and components (at least, in principle). * The simplest is an SWR me ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
