User Manual Part 2

Lynx.GX Installation and Management
USEFUL PATH CALCULATIONS
First Fresnel Distance Formula (USA)
The formula for calculating the first Fresnel distance is:
where:
F = first Fresnel Zone radius (feet)
D = path length (miles)
f = frequency (GHz)
d
1 = distance from first antenna (miles)
d2 = distance from second antenna (miles)
First Fresnel Distance Formula (international)
The formula for calculating the first Fresnel distance is:
where:
F = first Fresnel Zone radius (meters)
D = path length (kilometers)
f = frequency (GHz)
d
1 = distance from first antenna (kilometers)
d2 = distance from second antenna (kilometers)
Earth Curvature Formula (USA)
Clearance for terrain can be determined from accurate topographic maps (the height of trees and/or
buildings needs to be considered). Alternatively, the path can be surveyed along the direct route.
Clearance for earth curvature can be calculated for various "K" factors using the formula:
h = d
1
x d
2
/ 1.5 x K
K is the equivalent earth radius and under normal atmospheric conditions, K = 4/3 to give:
h = d
1
x d
2
/ 2
where:
h = change in vertical distance from a horizontal line (feet)
d = distance from first antenna (miles)
d = distance from second antenna (miles)
Appendix A. Installation Planning 48