CHAPTER 8
ANTENNA SETUPS
Revised: 11 Aug 08
8-11
EST P/N AA107D
FRESNEL ZONE
The Fresnel zone shows the ellipsoid spread of the radio waves around the visual line-of-sight after they leave the antenna (see
figure above). This area must be clear of obstructions or the signal strength will be reduced due to signal blockage. Typically,
20% Fresnel Zone blockage introduces little signal loss to the link. Beyond 40% blockage, signal loss will become significant.
This calculation is based on a flat earth. It does not take into account the curvature of the earth. It is recommended for RF path
links greater than 7 miles to have a microwave path analysis done that takes the curvature of the earth and the topography of the
terrain into account.
Fresnel Zone Radius = 72.1 SQRT [(d1d2) / (F(d1 + d2)]
Units
Fresnel Zone Radius in feet.
d1 and d2 in statue miles
F in GHz