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A loading coil or load coil is an inductor that is inserted into an electronic circuit to increase its inductance. The term originated in the 19th century for inductors used to prevent signal distortion in long-distance telegraph transmission cables.
The coil is added at the base of the whip (called a base-loaded whip) or occasionally in the middle (center-loaded whip). In the most widely used form, the rubber ducky antenna, the loading coil is integrated with the antenna itself by making the whip out of a narrow helix of springy wire. The helix distributes the inductance along the antenna ...
With a vertical antenna a loading coil at the base of the antenna may be employed to cancel the reactive component of impedance; small loop antennas are tuned with parallel capacitors for this purpose. An antenna lead-in is the transmission line, or feed line, which connects the antenna to a transmitter or receiver.
A loop antenna is a radio antenna consisting of a loop or coil of wire, tubing, or other electrical conductor, that for transmitting is usually fed by a balanced power source or for receiving feeds a balanced load. Within this physical description there are two (possibly three) distinct types:
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Buried in the ground under the antenna is an enormous radial ground system, which forms the bottom 'plate' of the capacitor with the overhead top load. The antenna must be very large at the VLF frequencies used; the supporting masts are 250–300 metres (820–980 ft) high, and the topload is about 1,900 metres (6,200 ft) in diameter.
Diagram of a zig-zag shortwave LPA antenna. Black shows metallic conductors; red shows insulating supports. The log-periodic is commonly used as a transmitting antenna in high power shortwave broadcasting [ 15 ] stations because its broad bandwidth allows a single antenna to transmit on frequencies in multiple bands .
The G5RV antenna is a dipole antenna fed indirectly, through a carefully chosen length of 300 Ω or 450 Ω twin lead, which acts as an impedance matching network to connect (through a balun) to a standard 50 Ω coaxial transmission line. The sloper antenna is a slanted vertical dipole antenna attached to the top of a single tower. The element ...