Chapter 3: Signal Theory and Modulation #

Now that you’ve learned how circuits generate and amplify signals, it’s time to focus on the signals themselves. How do we encode information onto radio waves? What makes different transmission modes unique? And how do these signals behave as they travel from transmitter to receiver?

General privileges will let you use many bands and a variety of modulation methods. Understanding how these different modes work will help you choose the right technique for your communication needs, whether you’re chatting casually across town, participating in a worldwide contest, or providing emergency communications during a disaster.

In this chapter, we’ll explore both analog and digital modulation techniques. We’ll examine how single sideband (SSB) works, why it’s more efficient than AM, and how frequency modulation (FM) provides clarity in some situations. Our digital examples range from classic radioteletype (RTTY) to modern protocols like FT8 that can pull signals out of the noise.

We’ll also look at the technical aspects of signal bandwidth, frequency mixing, and how to avoid interference.