Chapter 4: Signals and Modulation #

On its own, an oscillator’s steady carrier says only that a transmitter is on. Every mode on the air, from SSB voice and FM repeaters to CW, FT8, and SSTV, is a different way of putting a message onto that carrier. Each choice also decides how much of the band the signal takes up.

Every mode, analog or digital, answers the same questions in its own way. How much spectrum does it occupy, and why? What keeps it from splattering or clicking? How does it balance speed, bandwidth, and reliability? Once you can ask them, even an unfamiliar warble on the band becomes a set of choices you can evaluate.