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Diagram of leaky feeder cable. A leaky feeder is a communications system used in underground mines and inside tunnels. [1] Manufacturers and cabling professionals use the term "radiating cable" [2] [3] [better source needed] [4] as this implies that the cable is designed to radiate: something that a typical coaxial cable is generally not intended to do.
In a radio antenna, the feed line (feedline), or feeder, is the cable or other transmission line that connects the antenna with the radio transmitter or receiver.In a transmitting antenna, it feeds the radio frequency (RF) current from the transmitter to the antenna, where the energy in the current is radiated as radio waves.
The connector reliably carries signals at frequencies up to 100 MHz. [1] The coupling shell has a 5 / 8 inch 24 tpi UNEF standard thread. [4] The most popular cable plug and corresponding chassis-mount socket carry the old Signal Corps labels PL-259 (plug #259) and SO-239 (socket #239). [12]
The cable has a characteristic impedance of 75 ohms, and a capacitance of around 20pF/ft (60pF/m). [1] The 75 ohm impedance matches a dipole antenna in free space. RG (for radio guide ) was originally a unit indicator for bulk radio frequency (RF) cable in the U.S. military's Joint Electronics Type Designation System .
Cross-section through a coaxial cable showing shielding and other layers. One example is a shielded cable, which has electromagnetic shielding in the form of a wire mesh surrounding an inner core conductor. The shielding impedes the escape of any signal from the core conductor, and also prevents signals from being added to the core conductor.
A grid leak resistor and capacitor unit from 1926. The 2 megohm cartridge resistor is replaceable so the user can try different values. The parallel capacitor is built into the holder. A grid leak detector is an electronic circuit that demodulates an amplitude modulated alternating current and amplifies the recovered modulating voltage. The ...
ASTEC UM 1286 UHF modulator, top cover taken off. An RF modulator (radio frequency modulator) is an electronic device used to convert signals from devices such as media players, VCRs and game consoles to a format that can be handled by a device designed to receive a modulated RF input, such as a radio or television receiver.
Tempest for Eliza is a program that uses a computer monitor to send out AM radio signals, making it possible to hear computer-generated music in a radio. Video eavesdropping demo at CeBIT 2006 by a Cambridge University security researcher; eckbox – unsuccessful or abandoned attempt in spring 2004 to build an open-source Van Eck phreaking ...