The main signal dissipates into multiple reflected signals causing substantial signal downgrade and may cause loss of received signal. RF encounters some type of uneven surface and is reflected into multiple directions. Occurs when a signals wavelength is larger than pieces of a medium the signal is reflecting from or passing through. RF shadow can occur causing dead coverage zones or receive degraded signals. Refraction, diffraction, shoaling Change of wave direction and height in nearshore area Important for longshore sediment transport and wave height. Characteristics of the obstructing object:ĭiffraction is caused by some sort of partial blockage such as a small hill or building that is between a transmitting radio and receiver. The wave nature of light leads to two very important properties:refraction, where the direction of light propagation is altered at theboundary between media of different densities, and diffraction, whichhas among its consequences that light can 'bend around corners'.Causes:Ĭonditions that must be met for diffraction to occur. The waves that do not encounter the object do not bend and maintain a shorter and original path. The waves that encounter the object bend around the object, taking a longer and different path. May cause lower data rates, re-transmissions and lead to reduced capacity.ĭiffraction is the bending and spreading around of an RF signal when it encounters an obstruction. k-factor 4/3 = Normal atmospheric conditions.k-factor 1 = Signal bending toward the earth.A k-factor is simply a value to represent the bend that is occurring. The refractive index is used in (not defined by) Snell's law, which relates the angle of incidence to the angle of refraction when light passes from one material into. where c is speed of light in vaccum, and v is velocity of light in the material. A ray of light being refracted in a plastic block. Refraction is measured based on the k-factor. The refractive index tells you the speed of light in a given material. By definition, the index of refraction for a vacuum is exactly 1. Not to be confused with Diffraction, the change in direction of a wave around an obstacle. ![]() This typically can happen as the RF signal passes through a medium with a different density, thus causing the direction of the wave to change.Ī change in refraction can typically appear when dealing with long-distance outdoor bridge links. Causes:Ĭreates multipath, which can degrade the strength and quality of the received signal as well as cause data corruption or cancel signals. If portions of the wave are reflected, new wave fronts appear from the reflection points. When a wave hits a smooth object that is larger than the wave itself, depending on the media, the wave may bounce in another direction.Īs a wave radiates from an antenna, it broadens and disperses. diffraction, the spreading of waves around obstacles.
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