How Antennas Work

Overview

Wi-Fi is a radio technology, and radio implies antennas. Every wireless access point and client adapter has an antenna. (Many access points have two.) Sometimes these antennas are embedded in the device's case or otherwise hidden, but they're there. And for most Wi-Fi work, what you get is good enough. Once you get everything hooked up and working you can squint a little and pretend it's magic rather than radio.

On the other hand, if your circumstances aren't ideal and things don't quite connect, understanding antennas becomes crucial. Some of Wi-Fi's inherent limitations can be circumvented with a little antenna smarts, and many of the more advanced things that Wi-Fi technology can do (like bridging two separate networks in two different buildings; see Chapter 16) actually focus on special-purpose antenna systems.

In this chapter I'm going to explain briefly how antennas work, how you connect them to your Wi-Fi hardware, and how you can make sense of radio power math, which includes antenna gains and cable losses and absolute power levels delivered by Wi-Fi access points and client adapters.

Let me say up front: This is a technical chapter. If you're simply going to equip a small home or office with a minimal Wi-Fi network, virtually nothing in this chapter has to be learned, so you can skip immediately to Chapter 9, in which I explain how to assemble and test a Wi-Fi network using 'stock' equipment. Later on, if you want to fool with external antennas, you can always come back for a second look.