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Often random wire antennas are also (inaccurately) referred to as long-wire antennas.There is no accepted minimum size, but actual long-wire antennas must be greater than at least a quarter-wavelength ( 1 / 4 λ) or perhaps greater than a half ( 1 / 2 λ) at the frequency the long wire antenna is used for, and even a half-wave may only be considered "long-ish" rather than "truly ...
The T²FD antenna was originally developed during WW II at the San Diego naval base for use on ships at sea, where antenna size is limited, but where the metal hull and salt water under the ship, or seaside station, makes an exceptionally good radio-frequency ground-plane. The design properties of the antenna make it ideal for use in small ...
Used as base station antennas for land mobile radio systems such as police, fire, ambulance, and taxi dispatchers, and sector antennas for cellular base stations. Curtain array A curtain array is any one of several designs for large, directional, long-distance, broadside transmitting array antennas used at HF by shortwave broadcasting stations.
Most commonly, folded-unipole designs were used to replace a shunt-fed antenna – a different broadcast antenna design that also has a grounded base. A "shunt-fed" (or "slant-wire") antenna comprises a grounded tower with the top of a sloping single-wire feed-line attached at a point on the mast that results in an approximate match to the ...
A three-element Yagi–Uda antenna used for long-distance communication in the shortwave bands by an amateur radio station. The longer reflector element ( left ), the driven element ( centre ), and the shorter director ( right ) each have a so-called trap (parallel LC circuit ) inserted along their conductors on each side, allowing the antenna ...
The J-pole antenna is an end-fed omnidirectional half-wave antenna that is matched to the feedline by a shorted quarter-wave parallel transmission line stub. [5] [1] [6] For a transmitting antenna to operate efficiently, absorbing all the power provided by its feedline, the antenna must be impedance matched to the line; it must have a resistance equal to the feedline's characteristic impedance.