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The radiation pattern of a thin wire antenna is easily predictable using antenna modeling.For a straight wire, the radiation pattern can be described by axially symmetric multipole moments with no component along the wire direction; as the length of the wire is increased, higher multipole contributions become more prominent and multiple lobes (maxima) at angles to the antenna axis develop. [4]
The ground rods create a ground plane under the antenna which increases the gain. The ground rods may extend horizontally from the base, but in antennas fed by coaxial cable as shown here they are usually sloped downward to increase the radiation resistance of the antenna from the 36 ohms of a quarter wave monopole closer to 50 ohms, so the ...
A whip antenna is an antenna consisting of a straight flexible wire or rod. The bottom end of the whip is connected to the radio receiver or transmitter. A whip antenna is a form of monopole antenna. The antenna is designed to be flexible so that it does not break easily, and the name is derived from the whip-like motion that it exhibits when ...
English: Diagram of an umbrella antenna, a toploaded wire transmitting antenna used in the medium frequency (MF), low frequency (LF) and very low frequency (VLF) bands. It consists of a steel mast (grey) insulated from the ground, with diagonal wires radiating from the top, anchored to the ground in a circle around it. The feedline from the ...
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.
[ab] The simple antennas used to make a Yagi-Uda can either all be linear or bent linear antennas, or all loops (a quad antenna) or (rarely) a mixed combination of loops and straight-wire antennas. Yagi–Udas are used for rooftop television antennas , point-to-point communication links, and long distance shortwave communication using skywave ...
Patch antenna gain pattern. A directional antenna or beam antenna is an antenna which radiates or receives greater radio wave power in specific directions. Directional antennas can radiate radio waves in beams, when greater concentration of radiation in a certain direction is desired, or in receiving antennas receive radio waves from one specific direction only.
It usually consists of a single wire or network of horizontal wires, parallel to the ground, suspended above the ground under the antenna, connected to the receiver or transmitter's "ground" wire. [2] The counterpoise functions as one plate of a large capacitor, with the conductive layers of the earth acting as the other plate. [2] [3]