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Tests done by J.S. Belrose (1994) [7] showed that though the conventional T²FD length is close to a full-size 80 meter (3.5–4.0 MHz) antenna, the antenna starts to suffer serious signal loss both on transmit and receive below 10 MHz (30 m), with the 80 meter band signals −10 dB down (90% power loss) from a reference dipole at 10 MHz.
A fan monopole, or multi-monopole is a half of a fan dipole: It combines several different-sized monopole antennas, all sharing the same feedpoint, with each sized to transmit well on a different band or sub-band. Like all monopoles, it requires a ground system to function.
German physicist Heinrich Hertz first demonstrated the existence of radio waves in 1887 using what we now know as a dipole antenna (with capacitative end-loading). On the other hand, Guglielmo Marconi empirically found that he could just ground the transmitter (or one side of a transmission line, if used) dispensing with one half of the antenna, thus realizing the vertical or monopole antenna.
The nominal "80 meter" band begins at 3.5 MHz (85.7 m wavelength) and goes up to 4.0 MHz (74.9 m wavelength).The upper part of the band, mostly used for voice, is often referred to as 75 meters, since in Region 2, the wavelengths in that section are between 80–75 meters (adjacent to or overlapping a shortwave broadcast band called by the same name: "75 m").
This simplified arrangement has several advantages, including a shorter ground distance between the ends. For example, a dipole antenna for the 80 meter band requires a ground length of about 140 feet (43 m) from end to end. An inverted vee with a 40-foot (12 m) apex elevation requires only 115 feet (35 m).
In general terms, at any given frequency the log-periodic design operates somewhat similar to a three-element Yagi antenna; the dipole element closest to resonant at the operating frequency acts as a driven element, with the two adjacent elements on either side as director and reflector to increase the gain, the shorter element in front acting ...
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 ...
If the several dipole pairs are near the same length, the antenna will show a continuous range of matched-impedance frequencies wider than any one dipole. If the dipole pairs' lengths have wider size differences, the fan dipole will show multiple distinct resonant frequencies, at least one resonance for each pair.