PLANET WNAP-7200 - Manual (Page 73)

APPENDIX D. ANTENNA HEIGHT
The reliable wireless linkage usually depends on the both sides’ antennas for a clear radio
line of sight. The minimum height is up to the link distance, obstacles that may be in the path,
topology of the terrain, and the curvature of the earth (for links over 2 miles). For the
long-distance links, the mast or the pole may need to be constructed to attain the minimum
required height. The following table is for you to estimate the required minimum clearance
above the ground or path obstruction.
Total link distance
Max clearance for 60% of
first Fresnel zone at 5.8GHz
Approximate clearance
for earth curvature
Total clearance required
at mid-point of link
0.25 mile (402 m) 4.5 ft (1.4 m) 0 4.5 ft (1.4 m)
0.5 mile (805 m) 6.4 ft (1.95 m) 0 6.4 ft (1.95 m)
1 mile (1.6 km) 9 ft (2.7 m) 0 9 ft (2.7 m)
2 mile (3.2 km) 12.7 ft (3.9 m) 1 ft (0.3 m) 13.7 ft (4.2 m)
3 mile (4.8 km) 15.6 ft (4.8 m) 2 ft (0.6 m) 17.6 ft (5.4 m)
4 mile (6.4 km) 18 ft (5.5 m) 3 ft (0.9 m) 21 ft (6.4 m)
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