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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. [7]
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).
On the two meter band, the most common directional antennas used by competitors are two or three element Yagi antennas made from flexible steel tape. This kind of antenna has a cardioid receiving pattern , which means that it has one peak direction where the received signal will be the strongest, and a null direction, 180° from the peak, in ...
A competing third criterion is the number and bandwidth of the frequenc(y/ies) that a single antenna intercepts or emits. A fourth design goal is to make the antenna directional: To project or intercept radio waves from only one vertical and / or horizontal direction as exclusively as possible. Simple antennas
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 ...
When alternating current flows in a conductor it radiates an electromagnetic wave (radio wave). In multi-element antennas, the fields due to currents in one element induce currents in the other elements. Antennas are self-interacting in this respect; the waves reradiated by the elements superimpose on the original radio signal being studied.
The Adcock antenna is an antenna array consisting of four equidistant vertical elements which can be used to transmit or receive directional radio waves. The Adcock array was invented and patented by British engineer Frank Adcock and since his August 1919 British Patent No. 130,490, the 'Adcock Aerial' has been used for a variety of ...
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