User guide

RLX-IH ♦ 802.11b Reference
Industrial Hotspot
Page 82 of 99 ProSoft Technology, Inc.
April 10, 2007
and beam width depend on the overall antenna geometry, including the number
of elements, element spacing, and element length, but they are generally
proportional to the length, where longer length produces a narrower beam.
Sometimes the antenna is enclosed in a protective tube that hides the actual
antenna geometry.
The antenna gain also varies with antenna geometry, but generally is
proportional to the length, where longer length produces higher gain. Typical
values are 6 to 15 dBi. The antenna polarity is linear (parallel to the elements,
perpendicular to the boom).
Parabolic reflector antennas
A parabolic reflector antenna consists of a parabolic shaped dish and a feed
antenna located in front of the dish. Power is radiated from the feed antenna
toward the reflector. Due to the parabolic shape, the reflector concentrates the
radiation into a narrow pattern, resulting in a high- gain beam.
The antenna pattern is a beam pointed away from the concave side of the dish.
Beam width and antenna gain vary with the size of the reflector and the antenna
construction. Typical gain values are 15 to 30 dBi.
The antenna polarity depends on the feed antenna polarization.