There is some free antenna simulation software available on the Web called 4NEC2. The basis of the simulation is the “Numerical Electromagnetic Code,” hence NEC. This software can be used to simulate thousands of different antennas. One such antenna is our sweet little waveguide

The antenna radiation patterns in Figure 3-21 are for a common dipole omnidirectional antenna. This type of antenna simulation makes distinction between the vertical versus horizontal. An omni antenna radiation pattern looks a lot like a flattened donut. The diagram in Figure 3-22 shows the relationship between the two pattern diagrams. Notice the vertical plane is perpendicular to the Earth’s surface, while the horizontal plane is parallel to the Earth’s surface. Each plane is like a two-dimensional slice or circle with the center of the slice at the center of the antenna.

Moreover, 4NEC2 has a neat 3-D engine to show you what the antenna would look like if you could see RF radiation. See the screenshot in Figure 3-23 for a 3-D simulation of the can antenna from this chapter.

This antenna works great in one general direction. Also, it has about the same gain vertically as it does horizontally.

In this chapter, you learned about waveguides and the types of can antennas you can build on your own. The waveguide antenna is very easy to build, but you need to know where to drill. You also learned about antenna simulation and what antenna radiation patterns are and how to read them. With the knowledge from this chapter, you can go on to build and experiment with many different types of antennas. And understanding antenna radiation patterns puts you in the driver’s seat when choosing what antenna would work best for any situation.

Next up, let’s add a high-gain antenna to your wireless access point. You’ll learn how to choose the antenna type: omni versus directional. And you’ll find out how to stay within the spirit of the law when it comes to RF power. Read on to get the maximum range out of your wireless network.