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German physicist Heinrich Hertz first demonstrated the existence of radio waves in 1887 using what we now know as a dipole antenna (with capacitative end-loading). On the other hand, Guglielmo Marconi empirically found that he could just ground the transmitter (or one side of a transmission line, if used) dispensing with one half of the antenna, thus realizing the vertical or monopole antenna.
Animated diagram of a half-wave dipole antenna receiving a radio wave. The antenna consists of two metal rods connected to a receiver R. The electric field (E, green arrows) of the incoming wave results in oscillation of the electrons in the rods, charging the ends alternately positive (+) and negative (−).
In most antennas, the radiation from the different parts of the antenna interferes at some angles; the radiation pattern of the antenna can be considered an interference pattern. This results in minimum or zero radiation at certain angles where the radio waves from the different parts arrive out of phase , and local maxima of radiation at other ...
Connection diagram for a gamma matched halo antenna. The distribution of current along the two arms of a halo antenna is similar to the currents along the two arms (also a quarter wavelength long) of a half-wave dipole (see the animation there), being largest at the feedpoint and dropping to zero at the ends (the gap in the case of the halo ...
Drawing of a Yagi–Uda VHF television antenna used for analog channels 2–4, 54–72 MHz (U.S. channels). It has four parasitic elements: three directors (to left) and one reflector (to right) and one driven element which is a folded dipole (double rod) connected to a 300 Ω twin lead feedline down the mast to the television set.
Dipole field strength in free space, in telecommunications, is the electric field strength caused by a half wave dipole under ideal conditions. The actual field strength in terrestrial environments is calculated by empirical formulas based on this field strength.
Printable version; Appearance. move to sidebar hide. From Wikipedia, the free encyclopedia. Redirect page. Redirect to: Dipole antenna#Half-wave antenna;
The quarter-wave monopole and half-wave dipole both have vertical radiation patterns consisting of a single broad lobe with maximum radiation in horizontal directions, so they are popular. The quarter-wave monopole, the most compact resonant antenna, may be the most widely used antenna in the world.