ZyXEL Communications MAX-306, Руководство пользователя, Страница: 326 / 405

Appendix C Wireless LANs
User’s Guide
326
Types of Antennas for WLAN
There are two types of antennas used for wireless LAN applications.
• Omni-directional antennas send the RF signal out in all directions on a horizontal
plane. The coverage area is torus-shaped (like a donut) which makes these
antennas ideal for a room environment. With a wide coverage area, it is possible
to make circular overlapping coverage areas with multiple access points.
• Directional antennas concentrate the RF signal in a beam, like a flashlight does
with the light from its bulb. The angle of the beam determines the width of the
coverage pattern. Angles typically range from 20 degrees (very directional) to
120 degrees (less directional). Directional antennas are ideal for hallways and
outdoor point-to-point applications.
Positioning Antennas
In general, antennas should be mounted as high as practically possible and free of
obstructions. In point-to–point application, position both antennas at the same
height and in a direct line of sight to each other to attain the best performance.
For omni-directional antennas mounted on a table, desk, and so on, point the
antenna up. For omni-directional antennas mounted on a wall or ceiling, point the
antenna down. For a single AP application, place omni-directional antennas as
close to the center of the coverage area as possible.
For directional antennas, point the antenna in the direction of the desired
coverage area.