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A helical antenna is an antenna consisting of one or more conducting wires wound in the form of a helix.A helical antenna made of one helical wire, the most common type, is called monofilar, while antennas with two or four wires in a helix are called bifilar, or quadrifilar, respectively.
2.4 GHz helical antenna radiation pattern (NEC simulation) The Numerical Electromagnetics Code , or NEC , is a popular antenna modeling computer program for wire and surface antennas . It was originally written in FORTRAN during the 1970s by Gerald Burke and Andrew Poggio of the Lawrence Livermore National Laboratory .
VHF transmitter T-23/ARC-5 and HF transmitter T-20/ARC-5 on rack MT-71/ARC-5. The AN/ARC-5 Command Radio Set is a series of radio receivers, transmitters, and accessories carried aboard U.S. Navy aircraft during World War II and for some years afterward.
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 ...
The high reactance vs the low resistance give the antenna a high Q factor; the antenna and coil act as a high Q tuned circuit, reducing the usable bandwidth of the antenna. At lower frequencies mast radiators are replaced by more elaborate capacitively toploaded antennas such as the T antenna or umbrella antenna which can have higher efficiency.
To make an electrically short antenna resonant, a loading coil is inserted in series with the antenna. The coil is built to have an inductive reactance equal and opposite to the capacitive reactance of the short antenna, so the combination of reactances cancels. When so loaded the antenna presents a pure resistance to the transmission line ...
Omnidirectional radiation patterns are produced by the simplest practical antennas, monopole and dipole antennas, consisting of one or two straight rod conductors on a common axis. Antenna gain (G) is defined as antenna efficiency (e) multiplied by antenna directivity (D) which is expressed mathematically as: =.
Conformal antennas are a form of phased array antenna. They are composed of an array of many identical small flat antenna elements, such as dipole, horn, or patch antennas, covering the surface. At each antenna the current from the transmitter passes through a phase shifter device which are all controlled by a microprocessor (computer).