2 cissp ® Official Study Guide Eighth Edition

Antenna Types
A wide variety of antenna types can be used for wireless clients and base stations. Many 
devices can have their standard antennas replaced with stronger (i.e., signal-boosting) 
antennas.
The standard straight or pole antenna is an 
omnidirectional antenna
that can send and 
receive signals in all directions perpendicular to the line of the antenna itself. This is the 
type of antenna found on most base stations and some client devices. This type of antenna 
is sometimes also called a base antenna or a rubber duck antenna (due to the fact that most 
are covered in a flexible rubber coating).
Most other types of antennas are directional, meaning they focus their sending and 
receiving capabilities in one primary direction. Some examples of 
directional antennas
include Yagi, cantenna, panel, and parabolic. A Yagi antenna is similar in structure to that 
of traditional roof TV antennas. Yagi antennas are crafted from a straight bar with cross 
sections to catch specific radio frequencies in the direction of the main bar. Cantennas are 
constructed from tubes with one sealed end. They focus along the direction of the open end 
of the tube. Some of the first cantennas were crafted from Pringles cans. Panel antennas are 
flat devices that focus from only one side of the panel. Parabolic antennas are used to focus 
signals from very long distances or weak sources.
Adjusting Power Level Controls
Some wireless access points provide a physical or logical adjustment of the antenna power 
levels. Power level controls are typically set by the manufacturer to a setting that is suitable 
for most situations. However, if after performing site surveys and adjusting antenna place-
ment, wireless signals are still not satisfactory, power level adjustment might be necessary. 
However, keep in mind that changing channels, avoiding reflective and signal-scattering 
surfaces, and reducing interference can often be more significant in terms of improving con-
nectivity reliability.
When adjusting power levels, make minor adjustments instead of attempting to maxi-
mize or minimize the setting. Also, take note of the initial/default setting so you can return 
to that setting if desired. After each power level adjustment, reset/reboot the wireless access 
point before re-performing site survey and quality tests. Sometimes lowering the power 
level can improve performance. It is important to keep in mind that some wireless access 
points are capable of providing higher power levels than are allowed by regulations in 
countries where they are available.

---

Wireless Networks