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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.
terminated coaxial cage monopole The TC²M is a vertical polarized broadband shortwave antenna. The antenna can be characterized by being a vertical traveling-wave coaxially caged monopole over a ground plane, or alternatively described as a folded unipole with a terminating resistor. [5] off-center fed dipole antennas
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 ...
The antenna can be erected as horizontal dipole, as sloper, or an inverted-V antenna. With a transmatch , (antenna tuner) it can operate on all HF amateur radio bands (3.5–30 MHz ). [ 5 ] [ 6 ]
The two-wire version is often described as a "squashed loop antenna", since the total length of wire is one wavelength, and efficiency / radiation resistance of the folded dipole is very high: 4× that of a single dipole, [citation needed] analogous to the high efficiency of large loops. Any number of similar parallel wires may be added, with ...
The extra bandwidth comes from the controlled taper and large termination radius of the cone. The cone shape and flat disk disperse the local electric field. This reduces stored energy in the electric field, reducing antenna Q while also reducing losses. The elevation pattern might be distorted with grating lobes.
It is a two element Yagi-Uda antenna with folded dipole elements, and no director(s). Because of the folded ends, the element lengths are approximately 70% of the equivalent dipole length. The two-element design gives modest directivity (about 2.0 dB ) with a null towards the rear of the antenna, yielding a high front-to-back ratio : Gain up to ...