User Manual Part 2

Lynx.GX Installation and Management
Earth Curvature Formula (international)
Clearance for terrain can be determined from accurate topographic maps (the height of trees and/or buildings
must 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
/ 12.75 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 (meters)
d = distance from first antenna (kilometers)
d = distance from second antenna (kilometers)
Path Loss Attenuation (USA)
The formula for calculating the path loss attenuation is:
Lp (dB) = 96.6 + 20 log
10
F + 20 log
10
D
where:
F is in GHz
D is in miles
Path Loss Attenuation (international)
The formula for calculating the path loss attenuation is:
Lp (dB) = 92.4 + 20 log
10
F + 20 log
10
D
where:
F is in GHz
D is in kilometers
Reflection Point (USA)
The formula for calculating the position of the reflection point on a path is
for K = 4/3
h
1
/d
1
– d
1
/2 = h
2
/d
2
– d
2
/2
for K = 2/3 h
1
/d
1
– d
1
= h
2
/d
2
– d
1
for K = ∞ d
1
= D • h
1
/(h
1
– h
2
.)
where:
h is in feet
d and D are in miles
(The K factor allows for consideration of atmospheric conditions by allowing for the path of the beam, relative to
the earth. K = 4/3 is normal for atmospheric conditions and K = infinity is for worst case flat-earth propagation
conditions.)
Appendix A. Installation Planning 49