Dell PowerConnect W-IAP175P Installation Manual page 10

Table 5 Antenna Minimum Height and Clearance Requirements
Total Link Distance
4 miles (6.4 km)
5 miles (8 km)
7 miles (11.3 km)
9 miles (14.5 km)
12 miles (19.3 km)
15 miles (24.1 km)
NOTE: 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 5 Antenna Height and Line of Sight
2.4 m
20 m
A wireless bridge or mesh link is deployed to connect building A to building B, which is located three miles (4.8
km) away. Mid-way between the two buildings is a small tree-covered hill. From the above table it can be seen
that for a three-mile link, the object clearance required at the mid-point is 4.7 m (15.4 ft). The tree tops on the
hill are at an elevation of 17.7 m (58.1 ft), so the antennas at each end of the link need to be at least 22.4 m (73.5
ft) high. Building A is six stories high, or 20 m (66 ft), so a 2.4 m (7.9 ft) mast or pole must be constructed on its
roof to achieve the required antenna height. Building B is only three stories high, or 9 m (30 ft), but is located at
an elevation that is 12 m (39 ft) higher than building A. To mount an antenna at the required height on building
B, a mast or pole of 1.4 m (4.6 ft) is needed.
CAUTION: Never construct a radio mast, pole, or tower near overhead power lines.
NOTE: Local regulations may limit or prevent construction of a high radio mast or tower. If your wireless bridge or mesh link
requires a high radio mast or tower, consult a professional contractor for advice.
10
Max Clearance for
60% of First Fresnel
Zone at 5.8 GHz
17.7 ft (5.4 m)
20 ft (6.1 m)
23.6 ft (7.2 m)
27 ft (8.2 m)
30.8 ft (9.4 m)
34.4 ft (10.5 m)
Visual Line of Sight
A
Approximate Clearance
for Earth Curvature
2.0 ft (0.6 m)
3.0 ft (0.9 m)
6.2 ft (1.9 m)
10.2 ft (3.1 m)
18.0 ft (5.5 m)
28.0 ft (8.5 m)
3 miles (4.8 km)
4.7 m
17.7 m
Dell PowerConnect W-IAP175 Outdoor Instant Access Point | Installation Guide
Total Clearance
Required at
Mid-point of Link
19.7 ft (6.0 m)
23 ft (7.0 m)
30 ft (9.1 m)
37 ft (11.3 m)
49 ft (14.9 m)
62.7 ft (19.1 m)
Figure 5.
Radio Line of Sight
B
1.4 m
9 m
12 m