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An antenna such as the one described above is usable for both local and medium-long-distance communication across a frequency range of about 1:6 . For example, an antenna for the lower portion of shortwave (say, 3–18 MHz) will be roughly 33 m (110 feet) long, with conductors spaced 1 m (3.3 feet). For the higher portion of shortwave (5–30 ...
The top shows the directive pattern of a horn antenna, the bottom shows the omnidirectional pattern of a simple vertical dipole antenna. In the field of antenna design the term radiation pattern (or antenna pattern or far-field pattern) refers to the directional (angular) dependence of the strength of the radio waves from the antenna or other ...
In both cases the antenna proper is just the wire portion, and lead, balun, resistor, insulators, wires etc. are just the things you add to keep the wire in the right shape and to properly bring the electric signal to the antenna or away from it. Sorry! The two names are rather false friends, although the two antennas look much the same.
An NVIS antenna configuration is a horizontally polarized (parallel with the surface of the earth) radiating element that is from 1 / 20 th wavelength to 1 / 4 wave above the ground. The optimum height of such an antenna is about 1 / 4 wavelength, and high angle radiation declines only slightly for heights up to about ...
Antenna noise temperature is not the physical temperature of the antenna but rather an expression of the available noise power at the antenna flange. Moreover, an antenna does not have an intrinsic "antenna temperature" associated with it; rather the temperature depends on its gain pattern and the thermal environment that it is placed in ...
A reconfigurable antenna is an antenna capable of modifying its frequency and radiation properties dynamically, in a controlled and reversible manner. [2] In order to provide a dynamic response, reconfigurable antennas integrate an inner mechanism (such as RF switches, varactors, mechanical actuators or tunable materials) that enable the intentional redistribution of the RF currents over the ...
The biconical antenna has a broad bandwidth because it is an example of a traveling wave structure; the analysis for a theoretical infinite antenna resembles that of a transmission line. For an infinite antenna, the characteristic impedance at the point of connection is a function of the cone angle only and is independent of the frequency.
Patterned Vivaldi antenna, made from double-sided printed circuit board material. The feedline excites an open space via a microstrip line or coaxial cable, and may be terminated with either a sector-shaped area or a direct coaxial connection. From the open space, the signal traverses an exponentially tapered pattern via a symmetrical slot line.