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A half-wave dipole antenna consists of two quarter-wavelength conductors placed end to end for a total length of approximately ℓ = 1 / 2 λ. The current distribution is that of a standing wave , approximately sinusoidal along the length of the dipole, with a node at each end and an antinode (peak current) at the center (feedpoint ...
When the two arms of a dipole are individually straight, but bent towards each other in a 'V' shape, at an angle noticeably less than 180°, the dipole is called a 'V' antenna, and when the dipole arms' end closer to the ground than their center branch-point, the antenna is called an inverted-'V' . The inverted-'V' is popular since it provides ...
For instance, if a radio wave passing a given location has a flux of 1 pW / m 2 (10 −12 Watts per square meter) and an antenna has an effective area of 12 m 2, then the antenna would deliver 12 pW of RF power to the receiver (30 microvolts RMS at 75 ohms). Since the receiving antenna is not equally sensitive to signals received from all ...
The addition of parasitic elements gives a diminishing improvement in the antenna's gain. [2] Adding a reflector to a dipole, to make a 2 element Yagi, increases the gain by about 5 dB over the dipole. Adding a director to this, to give a 3 element Yagi, gives a gain of about 7 dB over a dipole. As a rule of thumb, each additional parasitic ...
To adjust the matching network the simplest instrument to measure the degree of mismatch between the feedline and the antenna is called an SWR meter (standing wave ratio meter), which reports the standing wave ratio (SWR) on the line: The ratio of the adjacent maximum and minimum voltage or current on the line. A ratio of 1:1 indicates an ...
The electric field strength at a specific point can be determined from the power delivered to the transmitting antenna, its geometry and radiation resistance. Consider the case of a center-fed half-wave dipole antenna in free space, where the total length L is equal to one half wavelength (λ/2). If constructed from thin conductors, the current ...
In radio communication, a ground dipole, [1] also referred to as an earth dipole antenna, transmission line antenna, [1] and in technical literature as a horizontal electric dipole (HED), [1] [2] [3] is a huge, specialized type of radio antenna that radiates extremely low frequency (ELF) electromagnetic waves.
This will often be a half-wave dipole, a very well understood and repeatable antenna that can be easily built for any frequency. The directive gain of a half-wave dipole with respect to the isotropic radiator is known to be 1.64 and it can be made nearly 100% efficient.