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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.
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).
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.
[f] The modern 'Windom' is a dipole which is fed approximately one third of the distance from one of its ends, but otherwise erected like an ordinary dipole, including most dipole variations (such as inverted-'V' and sloper dipoles). The strategically chosen offset feed location has a fairly high impedance, but fortuitously shows roughly the ...
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").
Loop antenna, receiver, and accessories used in amateur radio direction finding at 80-meter (260-foot) wavelength (3.5 MHz). As long as the loop perimeter is kept below about 1 / 4 wave, the directional response of small loop antennas includes a sharp null in the direction normal to the plane of the loop, so small loops are favored as ...
Transformers, autotransformers, and baluns are sometimes incorporated into the design of narrow band antenna tuners and antenna cabling connections. They will all usually have little effect on the resonant frequency of either the antenna or the narrow band transmitter circuits, but can widen the range of impedances that the antenna tuner can match, and/or convert between balanced and ...
The dipole elements are 15.55 metres (51.0 ft) and the impedance-matching symmetric feedline (ladder-line or twin-lead) can be either 300 Ω (8.84 metres or 29.0 feet) or 450 Ω (10.36 metres or 34.0 feet). [7]