Planet WAP-7000 [27/29] Antenna height

If there is any obstacle in the radio path, it may still be a radio link but the quality and the signal strength

will be affected. Ensuring the maximum clearance from objects on a path is important to locate the

antennas and the height. For the long-distance links, the radio signals might be lost partially due to the

non-LOS issue.

As we setup the radio path for the wireless bridge link, it needs to consider these factors:

 Avoid any partial line-of-sight between the antennas.

 Be aware of trees that may be near the path or obstruct the path.

 Make sure there is enough clearance from buildings and there is no

any building or construction blocking the path.

 Check the land topology between the antennas using topographical

maps, aerial photos, or even satellite image data.

 Avoid a path that may have the temporary blockage due to the

moving objects, such as cars, trains, or aircrafts.

Note: For the wireless link less than 500 m, the IEEE 802.11a radio signal will tolerate some obstacles in

the path and may not even require a visual line of sight between the antennas.

5.3.1 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)

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