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Often random wire antennas are also (inaccurately) referred to as long-wire antennas.There is no accepted minimum size, but actual long-wire antennas must be greater than at least a quarter-wavelength ( 1 / 4 λ) or perhaps greater than a half ( 1 / 2 λ) at the frequency the long wire antenna is used for, and even a half-wave may only be considered "long-ish" rather than "truly ...
The length is not critical, typically from one to two wavelengths end-to-end, but for any given length and frequency, there is an optimum acute angle at which the sections should meet. A horizontal rhombic antenna radiates horizontally polarized radio waves at a low elevation angle off the acute end of the antenna opposite the feedline.
Thus the electrical length of the antenna is longer than its physical length. The electrical length of an antenna element also depends on the length-to-diameter ratio of the conductor. [19] [15] [20] [21] As the ratio of the diameter to wavelength increases, the capacitance increases, so the node occurs farther beyond the end, and the ...
A dipole can be fed from very near its end (needing to be only about 1 / 20 th of the dipole length from the actual end) but the end impedances are exceedingly high – a few thousands of ohms, depending on the average height of the antenna and thickness of its wire.
Modeling an antenna with 100 wire segments requires 100 3 = 1 million calculations. Increasing the number of elements by a factor of 10 requires 1000 3 = 1 billion calculations, increasing the computing time by a factor of 1000, assuming the simulation completes at all given memory limitations and such. Consequently, there are other approaches ...
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).
The AT&T receiving Beverage antenna (left) and radio receiver (right) at Houlton, Maine, used for transatlantic telephone calls, from a 1920s magazine. The Beverage antenna or "wave antenna" is a long-wire receiving antenna mainly used in the low frequency and medium frequency radio bands, invented by Harold H. Beverage in 1921. [1]
Antenna directivity is the ratio of maximum radiation intensity (power per unit surface) radiated by the antenna in the maximum direction divided by the intensity radiated by a hypothetical isotropic antenna radiating the same total power as that antenna. For example, a hypothetical antenna which had a radiated pattern of a hemisphere (1/2 ...