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The most common type of dipole consists of two resonant elements, each just under a quarter wavelength long, hence a total length of about a half-wave. This antenna radiates maximally in directions perpendicular to the antenna's axis, giving it a small directive gain of 2.15 dBi (2.15 dBi means that in the direction of maximum radiation, signal ...
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.
The full wave loop (left) emits maximum power broadside to the wires with nulls off the sides, the small loop (right) emits maximum power in the plane of its wires with nulls broadside to the wires. Surprisingly, the radiation and receiving pattern of a small loop is perpendicular to that of a large self resonant loop (whose perimeter is close ...
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 ...
It is a simple half-wave dipole antenna used to receive the VHF television bands, consisting in the US of 54 to 88 MHz and 174 to 216 MHz , with wavelengths of 5.5 to 1.4 m (18 to 5 feet). It is constructed of two telescoping rods attached to a base, which extend out to about 1 m (3.3 feet) length (approximately one-quarter wavelength at 54 MHz ...
A full-wave loop antenna is slightly more than two half-wavelengths in circumference, which is a bit more than double the size of a halo antenna designed to operate on the same frequency. In contrast, the two semi-circles of a resonant loop, each is a half wavelength long.
The driven element of the antenna is usually a half-wave dipole, its length half a wavelength of the radio waves used. The parasitic elements are of two types. A "reflector" is slightly longer (around 5%) than a half-wavelength. It serves to reflect the radio waves in the opposite direction.
In transmitting antennas the impedance of the antenna must be matched to the feedline for maximum power transfer. A half wave whip antenna (length of ) has somewhat higher gain than a quarter wave whip, but it has a current node at its feedpoint at the base of the rod so it has very high input impedance. If it was infinitely thin the antenna ...