Receive and process global radio signals
This tutorial is designed to explore software-defined radio (SDR). We will cover some radio frequency (RF) theory in order to have a foundation for the article. The goal is to configure an SDR USB dongle, for this tutorial on a Pi, to receive a broadcasted FM radio signal.
SDR is a radio frequency communications system built using software, rather than physical hardware circuits consisting of oscillators, filters, modulators/ demodulators and signal amplifiers, to transmit or receive a radio frequency broadcast signal.
SDR devices receive analogue radio signals through an antenna, and then using an analogue-to-digital converter (ADC) they digitise the signal that can be further processed using digital signal processing.
WHAT IS IN AN RF BROADCAST?
An RF broadcast is a transmitted carrier signal travelling through the air. The signal is encoded with information using a modulation method. Two common RF modulation methods are frequency modulation (FM) and amplitude modulation (AM). In FM the carrier signal frequency is up-shifted and down-shifted in carrier frequency relative to the data applied. In AM the carrier signal amplitude varies according to the data applied.
To extract the data from the RF signal you would require a receiver that matches the modulation technique the signal was broadcasted with. The receiver
