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Line of sight (LoS) propagation from an antenna. Line-of-sight propagation is a characteristic of electromagnetic radiation or acoustic wave propagation which means waves can only travel in a direct visual path from the source to the receiver without obstacles. [1] Electromagnetic transmission includes light emissions traveling in a straight line.
VHF transmission range is a function of transmitter power, receiver sensitivity, and distance to the horizon, since VHF signals propagate under normal conditions as a near line-of-sight phenomenon. The distance to the radio horizon is slightly extended over the geometric line of sight to the horizon, as radio waves are weakly bent back toward ...
ACARS can send messages over VHF if a VHF ground station network exists in the current area of the aircraft. VHF communication is line-of-sight propagation and the typical range is up to 200 nautical miles at high altitudes. Where VHF is absent, an HF network or satellite communication may be used if available.
Millimeter waves propagate solely by line-of-sight paths. They are not refracted by the ionosphere nor do they travel along the Earth as ground waves as lower frequency radio waves do. [4] At typical power densities they are blocked by building walls and suffer significant attenuation passing through foliage.
This corresponds to the following non-logarithmic gain model: =, where = / is the average multiplicative gain at the reference distance from the transmitter. This gain depends on factors such as carrier frequency, antenna heights and antenna gain, for example due to directional antennas; and = / is a stochastic process that reflects flat fading.
A link budget is an accounting of all of the power gains and losses that a communication signal experiences in a telecommunication system; from a transmitter, through a communication medium such as radio waves, cable, waveguide, or optical fiber, to the receiver.
If there is line-of-sight, the path from () to ′ is used since it will always be at least as short as the path from () to and to ′. This algorithm works only on uniform-cost grids. [ 6 ] AP Theta* [ 6 ] [ 11 ] is an optimization of Theta* that uses angle-propagation to decrease the cost of performing line-of-sight calculations to O (1) .
The ARC-231 Skyfire is a software-definable radio for military aircraft that provides two-way, multi-mode voice and data communications over a 30 to 512 MHz frequency range. It covers both line-of-sight Ultra High Frequency (UHF) and Very High Frequency (VHF) bands with AM , FM and SATCOM capabilities, [ 1 ] including Integrated Waveform (IW).