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The smaller of these loops are much less efficient than the extraordinary performance of full-sized, self-resonant loops, [14] or the moderate efficiency of monopoles, dipoles, and halos, but where space for a full wave loop or a half-wave dipole is not available, small loops can provide adequate communications with low-but-tolerable efficiency.
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").
Collinear dipole array on repeater for radio station JOHG-FM on Mt. Shibisan, Kagoshima, Japan. In telecommunications, a collinear antenna array (sometimes spelled colinear antenna array) is an array of dipole or quarter-wave antennas mounted in such a manner that the corresponding elements of each antenna are parallel and collinear; that is, they are located along a common axis.
A half wave whip antenna (length of ) has somewhat higher gain than a quarter wave whip, but it has a current node at its feedpoint at the base of the rod so it has very high input impedance. If it was infinitely thin the antenna would have an infinite input impedance, but the finite width gives typical, practical half wave whips an impedance ...
The quarter-wave monopole, the most compact resonant antenna, may be the most widely used antenna in the world. The five-eighth wave monopole – length 0.625 λ , or 5 / 8 of a wavelength – is also popular, since at that length monopoles direct the greatest proportion of their radiated power horizontally, hence the best use of ...
In radio propagation, horizontal plane is used to plot an antenna's relative field strength in relation to the ground (which directly affects a station's coverage area) on a polar graph. Normally the maximum of 1.000 or 0 dB is at the top, which is labeled 0 o , running clockwise back around to the top at 360°.
Ground wave is important for radio signals below 30 MHz, but is generally insignificant at higher frequencies where line-of-sight propagation dominates. AM and longwave broadcasting, navigation systems such as LORAN , low-frequency time signals , non-directional beacons , and short-range HF communications all make use of it.
SIW is known to have similar guided wave and mode characteristics to conventional rectangular waveguide with equivalent guide wavelength. Since the emergence of new communication technologies in the 1990s, there has been an increasing need for high-performance millimeter-wave systems.