User's Manual

26 Link CX User Manual, Version A
• Multipath Fading: See Figure 3-2. Because a Link CX terminal typically transmits its stron-
gest signals in a cone-shaped pattern, some of the signal may be reflected from a nearby
building, from water under the signal path, or from other RF reflectors. This reflected signal
can then be received by the far-end Link CX and superimposed on the main signal, usually
degrading the signal strength. To avoid multipath fading, interWAVE recommends that you
install the Link CX antenna on the back, rather than the front, of buildings to avoid multipath
fading from water or other ground-level surfaces, and that you plan radio links away from
nearby buildings.
Table 3-1 Beam Clearance Envelope at Midpath
Path Distance Midpath Minimum Beam Clearance Envelope (Note)
2 km 7 m
5 km 11 m
10 km 15 m
20 km 21 m
32 km 27 m
1 mile 20 ft
3 miles 34 ft
6 miles 48 ft
12 miles 69 ft
20 miles 88 ft
Note: The minimum beam clearance envelope is defined by the radius around the direct path
shown in Figure 3-1, within which there must be no obstacles.
The Fresnel zone surrounds the direct signal path, so it affects objects to
the side of the path as well as objects directly in the path.