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The most common type of dipole consists of two resonant elements, each just under a quarter wavelength long, hence a total length of about a half-wave. This antenna radiates maximally in directions perpendicular to the antenna's axis, giving it a small directive gain of 2.15 dBi (2.15 dBi means that in the direction of maximum radiation, signal ...
The voltage is constant only in the sense that at full power, the voltage in the system does not depend on the number of speakers driven (as long the amplifier's maximum power is not exceeded). [2] Constant-voltage speaker systems are also commonly referred to as 25- , 70- , 70.7- , 100 or 210-volt speaker systems ; distributed speaker systems ...
In some cases, an audio device may be measured by the total system power of all its loudspeakers by adding all their peak power ratings. Many home theater in a box systems are rated this way. Often low-end home theater systems' power ratings are taken at a high level of harmonic distortion as well; as high as 10%, which would be noticeable. [21]
A full-wave loop antenna is slightly more than two half-wavelengths in circumference, which is a bit more than double the size of a halo antenna designed to operate on the same frequency. In contrast, the two semi-circles of a resonant loop, each is a half wavelength long.
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.
The half-power point is the angle off boresight at which the antenna gain first falls to half power (approximately −3 dB) [a] from the peak. The angle between the −3 dB points is known as the half-power beam width (or simply beam width). [4] Beamwidth is usually but not always expressed in degrees and for the horizontal plane.