??Interference
Interference may be caused by another system on the same frequency range, external noise, or some other
The Line of Sight Concept
An optical line of sight exists if an imaginary straight line can be drawn connecting the antennas on either side of the link.
Clear Line of Sight
A clear line of sight exists when no physical objects obstruct viewing one antenna from the location of the other antenna.
A radio wave clear line of sight exists if a defined area around the optical line of sight (Fresnel Zone) is clear of obstacles.
Fresnel Zone
The Fresnel zone is the area of a circle around the line of sight. The Fresnel Zone is defined as follows:
Figure31: Fresnel Zone
R = ½ ? ???xD????????
R: radius of the first Fresnel zone.
???wavelength (expressed in feet).
D: distance between sites (expressed in Km).
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