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Trango Broadband Wireless — Access5830 User Manual Rev. F page 69
Signal Fading
Fading is any loss of signal from a wide variety of factors: RF noise, solar flares, variations in the atmosphere, internal noise in
the system, all play a role.
Multipath
The transmitted signal arrives at the receiver from different directions, with different path lengths, attenuation and delays. The
summed signal at the receiver may result in an attenuated signal.
Figure 9-4: Multipath Reception
Line of Sight
An optical line of sight exists if an imaginary straight line can connect the antennas on either side of the link. Radio wave clear
line of sight exists if a certain area around the optical line of sight (Fresnel zone) is clear of obstacles. Poor line of sight exists if
the first Fresnel zone is obscured.
• Link Budget Calculations
• Weather conditions (rain, wind, etc.) At high rain intensity (150 mm/hr), the fading of an RF signal at 5.8 GHz may
reach a maximum of 0.02 dB/Km, and wind may cause fading due to antenna motion.
• Interference: Interference may be caused by another system on the same frequency range, external noise, or some
other co-located system.
Radio 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:
Figure 9-5: Fresnel Zone Obstruction
When at least 80% of the first Fresnel Zone is clear of obstacles, propagation loss is equivalent to that of free space.