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A 20-meter-long T²FD antenna, covering the 5-30 MHz band. The Tilted Terminated Folded Dipole (T²FD, T2FD, or TTFD) or Balanced Termination, Folded Dipole (BTFD) - also known as W3HH antenna - is a general-purpose shortwave antenna developed in the late 1940s by the United States Navy.
A "folded dipole" type of halo, similar to the original halo patent. [1] Gain along Y axis 1.2 dBi, gain along Z axis −10 dBi, gain along X axis −1.7 dBi. Fed at the center of the bottom conductor (at the red mark; feed-line not shown), supported at the center of the top conductor which is at ground potential for RF.
A folded dipole is, technically, a folded full-wave loop antenna, where the loop has been bent at opposing ends and squashed into two parallel wires in a flat line. Although the broad bandwidth, high feedpoint impedance, and high efficiency are characteristics more similar to a full loop antenna, the folded dipole's radiation pattern is more ...
This shape-indifference allows otherwise prohibitively long dipoles to have their far ends bent sideways, folded over, or zig-zagged, in order to shorten the antenna to fit inside an available space. (The use of fold here is not the same as "fold" in "folded dipole" or "folded unipole".) This apparent mangling has very little affect on the ...
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.
Consider a Yagi–Uda consisting of a reflector, driven element, and a single director as shown here. The driven element is typically a 1 ⁄ 2 λ dipole or folded dipole and is the only member of the structure that is directly excited (electrically connected to the feedline). All the other elements are considered parasitic. That is, they ...
Moxon antenna for the 20-meter band.The antenna is the faint rectangle of wires held in tension by the bent X-shaped support frame. Moxon antenna for the 2-meter band. The Moxon antenna or Moxon rectangle is a simple and mechanically rugged two-element parasitic array, single-frequency antenna. [1]
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.
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