Explore Software Defined Radio

Chapter 4Digital Speech Decoding

Let’s revisit, for a moment, the old days before silicon integrated circuits and software packages and newfangled computing machines. Back then, an enterprising hobbyist could use some transistors, a few variable resistors, a diode or two, and a tunable crystal and, with the right antenna and a healthy dose of skill and talent, receive and listen to almost any signal on the air. Back then, all broadcast radio signals were analog. While UHF broadcasting existed, there was almost nothing transmitting in that area of the spectrum, and satellite radio was unheard of.

Nowadays, analog signals are gradually being replaced ...