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VHF radio is also used for marine Radio [8] as per its long-distance reachability comparing UHF frequencies. Example allocation of VHF–UHF frequencies: [9] Radionavigation 60: 84–86 MHz; Fixed Maritime Mobile: 130–135.7 MHz; Fixed Aeronautical radio navigation: 160–190 MHz; Broadcasting Aeronautical Radionavigation: 255–283.5 MHz
Umbrella antenna An elaborated and expanded version of a 'T' antenna; it is a very large wire transmitting antenna used on VLF bands for VLF time signals or long-range submarine communications. Umbrella antennas are enormous on human-scale but are paradoxically ultra-short antennas, relative to the even larger wavelengths they are built for.
High-gain antennas have the advantage of longer range and better signal quality, but must be aimed carefully at the other antenna. An example of a high-gain antenna is a parabolic dish such as a satellite television antenna. Low-gain antennas have shorter range, but the orientation of the antenna is relatively unimportant.
Indoor antennas are designed to be located on top of or next to the television set, but are ideally placed near a window in a room and as high up as possible for the best reception. [1] The most common types of indoor antennas are the dipole [2] ("rabbit ears"), which work best for VHF channels, and loop antennas, which work best for UHF. [3]
Omnidirectional radiation patterns are produced by the simplest practical antennas, monopole and dipole antennas, consisting of one or two straight rod conductors on a common axis. Antenna gain (G) is defined as antenna efficiency (e) multiplied by antenna directivity (D) which is expressed mathematically as: =.
Printer-friendly PDF version of the Communication Theory Wikibook. Licensing Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License , Version 1.2 or any later version published by the Free Software Foundation ; with no Invariant Sections, no Front-Cover Texts, and no Back ...
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.