Aruba AP-85, Руководство по установке

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Aruba AP-85 Outdoor Access Point Series | Installation Guide Outdoor Planning and Deployment Considerations | 17
z
Check the topology of the land between the antennas using topographical maps, aerial photos, or even satellite image
data (software packages are available that may include this information for your area)
z
Avoid a path that may incur temporary blockage due to the movement of cars, trains, or aircraft.
Antenna Height
A reliable wireless bridge or mesh link is usually best achieved by mounting the antennas at each end high enough for a clear
radio line of sight between them. The minimum height required depends on the distance of the link, obstacles that may be in
the path, topology of the terrain, and the curvature of the earth (for links over 3 miles).
For long-distance links, the AP may have to be mounted on masts or poles that are tall enough to attain the minimum
required clearance. Use the following table to estimate the required minimum clearance above the ground or path
obstruction (for 5 GHz bridge links).
Table 3 Antenna Minimum Height and Clearance Requirements
Total Link Distance
Max Clearance for
60% of First Fresnel
Zone at 5.8 GHz
Approximate Clearance
for Earth Curvature
Total Clearance
Required at
Mid-point of Link
0.25 mile (0.402 km) 4.6 ft (1.4 m) 0.007 ft (0.002 m) 4.6 ft (1.4 m)
0.5 mile (0.805 km) 6.2 ft (1.9 m) 0.03 ft (0.010 m) 6.2 ft (1.9 m)
1 mile (1.6 km) 8.9 ft (2.7 m) 0.13 ft (0.04 m) 8.9 ft (2.7 m)
2 miles (3.2 km) 12.5 ft (3.8 m) 0.5 ft (0.15 m) 13.1 ft (4.0 m)
3 miles (4.8 km) 15.4 ft (4.7 m) 1.0 ft (0.3 m) 16.4 ft (5.0 m)
4 miles (6.4 km) 17.7 ft (5.4 m) 2.0 ft (0.6 m) 19.7 ft (6.0 m)
5 miles (8 km) 20 ft (6.1 m) 3.0 ft (0.9 m) 23 ft (7.0 m)
7 miles (11.3 km) 23.6 ft (7.2 m) 6.2 ft (1.9 m) 30 ft (9.1 m)
9 miles (14.5 km) 27 ft (8.2 m) 10.2 ft (3.1 m) 37 ft (11.3 m)
12 miles (19.3 km) 30.8 ft (9.4 m) 18.0 ft (5.5 m) 49 ft (14.9 m)
15 miles (24.1 km) 34.4 ft (10.5 m) 28.0 ft (8.5 m) 62.7 ft (19.1 m)
N O T E
To avoid any obstruction along the path, the height of the object must be added to the minimum
clearance required for a clear radio line of sight. Consider the following simple example, illustrated in
Figure 9 .