User's Manual

Installation Prerequisites
21
For a link of 4 km, at 3.5 GHz produces a first Fresnel Zone radius clearance of about 9.3
meters, meaning the antennas should be mounted at a height of at least 5.6 meters (60%
of 9.3 meters) above ground level (or clutter level).
For a link of 4 km, at 4.9 GHz produces a first Fresnel Zone radius clearance of about 7.8
meters, meaning the antennas should be mounted at a height of at least 4.7 meters (60%
of 7.8 meters) above ground level (or clutter level).
Multipath Fading
Some of the transmitted signals may be reflected from a nearby building, by water under the
signal path, or from any other reflectors. This reflected ("bounced") signal can then be received
by the radio receiving the signal and superimposed on the main received signal, thereby
degrading the signal strength.
To avoid multipath fading from nearby buildings etc., Airspan recommends installing the
outdoor radios at the rear end of the buildings instead of at the front. When you install at the
rear end of the building, the front-end of the building blocks incoming signals from multipath
reflections.
Radio Antenna Alignment
Once the ProST is installed and aimed in the general direction of the base station, it is
recommended to measure the received signal strength (RSS) to determine the signal strength
received from the base station, and to precisely align the ProST for maximum signal strength.
You need to orientate (up/down, left/right) the ProST until the maximum RSSI levels are
achieved, and then secure the ProST. For viewing RSS values, see "Web-based Management"
for standard alignment, for finer alignment, see RSSI LED Plug Adapter
.