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The driving point impedance of a half-wave folded dipole is 4 times that of a simple half-wave dipole, thus closely matching that 300 Ω characteristic impedance. [19] [full citation needed] Most FM broadcast band tuners and older analog televisions include balanced 300 Ω antenna input terminals. However twin lead has the drawback that it is ...
Two dipole antennas mounted at right angles, fed with a phase difference of 90°. ... 1 / 4 wave tall, which is the minimum size for it to self-resonate. [n] ...
The monopole antenna is essentially one half of the half-wave dipole, a single 1 / 4 wavelength element with the other side connected to ground or an equivalent ground plane (or counterpoise). Monopoles, which are one-half the size of a dipole, are common for long-wavelength radio signals where a dipole would be impractically large.
Since a half-wave dipole has a gain of 2.19 dBi and a radiation resistance of 73 Ohms, a quarter-wave ( 1 / 4 λ) monopole will have a gain of 2.19 + 3.0 = 5.2 dBi and a radiation resistance of about 36.5 Ohms. [13] The antenna is resonant at this length, so its input impedance is purely resistive.
[4] At 1 / 2 wave, the halo antenna is near or on the extreme high limit of the size range for "small" loops, but unlike most oversized small loops, it can be analyzed with simple techniques by treating it as a bent dipole.
The antenna acts similarly to an electrically short dipole or monopole, equivalent to a 1 / 4 wave vertical and the radiation pattern, [citation needed] similar to these antennas is omnidirectional, with maximum radiation at right angles to the helix axis.