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A halo antenna is distinct from the small-loop antenna in size, [a] radiation resistance, and efficiency, but their radiation patterns are nearly the same. A halo antenna is a self-resonant antenna: Its feedpoint impedance is reactance-free / purely resistive at the design frequency.
The radiation pattern and especially the input impedance is affected by its proximity to the ground. If fed with higher frequencies the antenna input impedance will generally include a reactive part and a different resistive component, requiring use of an antenna tuner. As the frequency increases above the first harmonic, the radiation pattern ...
A halo antenna is a half-wave dipole bent into a circle for a nearly uniform radiation pattern in the plane of the circle. When the halo's circle is horizontal, it produces horizontally polarized radiation in a nearly omnidirectional pattern with only a little power wasted toward the zenith, compared to a straight horizontal dipole.
the upper half of a vertical full-wavelength loop antenna mounted on the ground (not to be confused with the visually similar but electrically different half-square antenna described below, under array antennas, [r] nor to be confused with the halo antenna, described next). The full loop is cut at two opposite points along its perimeter, and ...
The driving impedance of the antenna is equal to the characteristic impedance of the wire with respect to ground, somewhere between 400 and 800 ohms, depending on the height of the wire. Typically a length of 50-ohm or 75-ohm coaxial cable would be used for connecting the receiver to the antenna endpoint. A matching transformer should be ...
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.
A turnstile antenna, or crossed-dipole antenna, [1] is a radio antenna consisting of a set of two identical dipole antennas mounted at right angles to each other and fed in phase quadrature; the two currents applied to the dipoles are 90° out of phase. [2] [3] The name reflects the notion the antenna looks like a turnstile when mounted ...
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 ...