Antennas
The antenna couples radio after-effects amid the radio card’s transceiver and the air medium. The
transceiver converts agenda abstracts from the computer to a radio abundance (RF) arresting (and vice
versa). The antenna transmits and receives RF signals that back advice amid user
796 Appendix G: IEEE 802.11 Fundamentals
devices. Omnidirectional antennas, which appear with best admission points, anatomy a annular coverage
pattern about the antenna, as allotment A of Figure G-4 illustrates. In best cases, a aggregation will
install assorted admission credibility aural a facility, with omnidirectional antennas creating individual
radio beef that overlap with anniversary added to accommodate roaming. This about offers optimum
coverage over a ample calm breadth with a minimum cardinal of admission points.
Figure G-4 Wireless LAN Antenna Types and RF Arresting Patterns
As an another to omnidirectional antennas, charge antennas focus RF activity added in one
direction than others. Allotment B of Figure G-4 illustrates the advantage arrangement of a directional antenna.
These types of antennas are ideal for accouterment advantage over a beyond breadth for which it is not
practical to install admission points. For example, a account aggregation can install a directional antenna
to awning an alfresco breadth that is autumn ability transformers. The directional antenna transmits and
receives radio after-effects over best distances aural the advantage pattern, abundant as a flashlight
focuses ablaze in one direction.
Some antennas are disposable and others are integrated, so it ability not be accessible to change
an admission point’s antenna type. When purchasing admission points, ensure that the antennas are
removable behindhand of whether there are accepted affairs to use altered antennas. It ability be
necessary in the approaching to use the admission credibility with directional antennas.