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Isotron is the trade name for a shortwave antenna marketed by Bilal Co. for use as an amateur radio transmitting antenna for restricted spaces. [1] It is physically short as compared to a dipole antenna for a given frequency. It consists of a coil placed between two angled sheet metal plates.
In antenna terms, each of the conductors making up the antenna is known as an element. [9] To calculate the net result, NEC breaks the antenna's elements into a number of sampled points, called segments. It uses simple calculations based on the diameter of the conductor and the wavelength of the signal to determine the induced voltage and ...
In most antennas, the radiation from the different parts of the antenna interferes at some angles; the radiation pattern of the antenna can be considered an interference pattern. This results in minimum or zero radiation at certain angles where the radio waves from the different parts arrive out of phase , and local maxima of radiation at other ...
Although no real antenna can be exactly isotropic, a few antennas are built to be as near to isotropic as possible; they are used for emergency backup antennas and for test equipment for other antennas: Because the received and transmitted signal strength is the same in (almost) every direction, they work without any need for them to be any ...
The rhombic antenna is a directional wire antenna used on MF and HF bands for shortwave reception. The antenna consists of a wire suspended above the ground in the shape of a rhombus , terminated at one end by a resistor equal the the wire's characteristic impedance, about 400 to 600 ohms, and at the other end connected to the feedline to the ...
[40] [36] He credited Prof. Moisè Ascoli of Rome with first calculating in 1897 that the antenna radiated at a wavelength of four times its height. [38] An integral equation for the current in wire antennas was derived by Henry Pocklington in 1897, [38] [41] who showed the current was approximately a sinusoidal standing wave.
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 ...
The J-pole antenna is an end-fed omnidirectional half-wave antenna that is matched to the feedline by a shorted quarter-wave parallel transmission line stub. [5] [1] [6] For a transmitting antenna to operate efficiently, absorbing all the power provided by its feedline, the antenna must be impedance matched to the line; it must have a resistance equal to the feedline's characteristic impedance.