CEH

354 Chapter 15 ■ Wireless Networking

needed from site to site instead of covering a wider area. From a security standpoint, this

type of antenna enhances security by limiting signals to smaller areas.

FIGURE 15.1 A Yagi antenna

The next antenna type is one of the more common ones and is known as an

omnidirectional antenna. This type of antenna emanates radio energy in all directions, but

typically in some directions better than others. In many cases, these types of antennas can

transmit data in two dimensions well, but not in three dimensions.

A parabolic grid antenna (Figure 15.2) is another popular type of design and is commonly

seen in various applications. This type of antenna takes the form of a dish and is a directional

antenna because it sends and receives data over one axis; in fact, it can be said that this type

of antenna is unidirectional, working well only over a single axis and in one direction. One

big advantage of this type of antenna is that its dish catches parallel signals and focuses them

to a single receiving point, so it gets better signal quality and over longer ranges. In many

cases, this type of antenna can receive Wi-Fi signals over a distance of 10 miles.

FIGURE 15.2 A parabolic antenna