Line of Sight Clearance Calculations in Microwave Radio Link

Line of sight between transmitter and receiver is a straight line and ray bending due to K-value variation is added to the terrain heights.

The modification of terrain heights is given by
(d1 x d2) / (12.74 x k)
K=1.33 for path lengths between 5 to 15 Kms
K=0.66 for longer path lengths of 15 to 30 Kms

There must be a clearance for the first Fresnel zone to avoid diffraction loss in addition to free space loss.

Clearance of 100% or greater at k=4/3
Clearance of 60% or greater at lower k values
 In case of space diversity, the antenna can have a 60% clearance at k=4/3 plus allowance for tree growth, buildings (usually 3 meter)