27010912 Installation Precautions
To ensure that the antenna works at the optimal performance level, take the following installation precautions:
- Install the antenna upright and place one side of the RF cable connector towards the ground.
- When installing single-polarized antennas, keep the distance between two antennas to within 30 cm to 50 cm.
- Install the antenna away from metal obstructions, such as air conditioners or heating pipes. Do not install the antenna on a wire mesh.
- Wall materials and thickness determine the number of walls that radio signals can pass through. Factor that into antenna selection.
- Install lightning rods for outdoor antennas to prevent lightning strikes. For details on how to install a lightning rod, see section "Antenna Installation."
- Ensure that no obstacle exists in the Fresnel zone in bridging scenarios. That is, the antenna height must be larger than the sum of the radius of the first Fresnel zone and obstacle height.
As shown in the figure, the Fresnel zone refers to the ellipsoid. Obstacles in the zone will adversely affect signal transmissions. If not blocked, radio signals can travel in an approximate free space.
Fresnel zones differ depending on the Fresnel zone radius. In a free space, radio signals are mainly transmitted between antennas in the first Fresnel zone. In normal cases, the Fresnel zone refers to the first Fresnel zone.
The radius of the first Fresnel zone is calculated and related parameters are described as follows:
- r: indicates the radius of the first Fresnel zone, in meters.
- d: indicates the distance between two antennas, in km.
- f: indicates the signal frequency, in GHz.
With 5 GHz signals as an example, Table 18-2 lists the radius of the first Fresnel zone in different backhaul distances.