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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 ...
English: Diagram of a ground plane antenna, a common omnidirectional monopole antenna used at VHF and UHF frequencies. It consists of a vertical whip antenna one quarter wavelength long, with 3 or 4 quarter wave rods extending from the base electrically connected to the ground side of the transmission line.
[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 ...
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 antenna rod and its image together act like a dipole antenna of twice the length, so a monopole over an infinite, perfectly conducting plane has a radiation pattern identical to the top half of the pattern of a vertical dipole of twice the length. [1] [70] [71] For the quarter wave monopole, the antenna acts like a half wave dipole.
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.
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]
The angle of the slope is usually between 45°–60° and the lower end of the wire is at least 1 ⁄ 6 wavelength above the electrical ground. [3] A sloper is typically fed with a coaxial cable in the center, at the top of the center support mast. At least 1 ⁄ 4 of the wavelength of feedline must be at 90° angle to the antenna. [3]