Chapter 4 Digital Speech Decoding

Explore Software Defined Radio — by Wolfram Donat (18 / 30)

👈 Antenna Design for SDR Hobbyists | TOC | Hardware 👉

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 by digital ones. The day may not be far in the future when all signals on the airwaves are digital. Back in 2009, all U.S. analog television signals were shifted to digital, and in early 2019 the nation of Norway shut off all their national analog FM radio stations in favor of digital audio broadcasting. If and when that happens in your location, the type of radio set shown in the preceding image will no longer be useful. It will still pick up the signals, but they will be unintelligible to the listener.