Alvarion BreezeACCESS II, Системное руководство, Страница: 76 / 324

2-4
BreezeACCESS Version 4.5 Installation
Manual Revision: 1.0
! Position the antennas clear of metal furniture and away from
moving metal objects such as metal fans or doors.
Antenna Diversity
Multipath propagation is to be expected when there are potential
reflectors between the Access Unit and Subscriber Units. These
reflectors may be buildings or moving objects such as airplanes and
motor vehicles. If this is the case, the radio signal does not travel in a
straight line, but is reflected or deflected off of the object, creating
multiple propagation paths.
In applications where no multipath propagation is expected, a single
antenna is sufficient to ensure good performance levels. However, in
cases where multipath propagation exists, Alvarion recommends that
two antennas be used. This takes advantage of space diversity
capabilities. By using two antennas per unit, the system can select the
best antenna on a per-packet basis (every several milliseconds).
When installing a single antenna, configure the Transmit Antenna
option to either Antenna 1 or Antenna 2 , according to the antenna
being used. When using two antennas, configure the Transmit
Antenna option to Both Antennas .
Antenna Polarization
Antenna polarization must be the same at either end of the link. In most
applications, the preferred orientation is vertical polarization. Above
ground propagation of the signal is better when the antenna is polarized
vertically. For omni antennas, make sure that the antennas are
extended upward vertically in relation to the floor to achieve vertical
polarization. To verify polarization of detached antennas, refer to the
assembly instructions supplied with the antenna set.
Antenna Seal
When using outdoor antennas, you must seal the antenna connectors
against rain. Otherwise the antennas are not suitable for use in outdoor
installations.
Lightning Protection
Lightning protection is designed to protect people, property and
equipment by providing a path to the ground for the lightning’s energy.
The lightning arrestor diverts the strike energy to the ground along a
deliberate and controlled path instead of allowing it to choose a random
path. Lightning protection for a building is more forgiving than
protection of electronic devices. A building can withstand up to 100,000
volts, but electronic equipment may be damaged by just a few volts.