System-bus-radio is a software-defined radio transmitter that generates AM radio signals by modulating the electromagnetic emissions from a computer's processor and memory bus, without requiring any dedicated radio hardware or physical antennas. It functions as a CPU electromagnetic emissions tool and processor-based signal generator, enabling radio transmission through precise control of CPU instructions and memory bus operations.
The project encodes musical notes as sequences of frequency and duration pairs, then synthesizes the AM radio waveform in real-time by executing a tight loop of CPU instructions with precise delays. It exploits the natural electromagnetic radiation from the memory bus during read/write cycles to produce a modulated square-wave carrier signal, allowing playback of audio or data on a standard AM radio receiver placed near the computer.
This experimental approach to radio communication explores unconventional methods of signal generation through processor-level electromagnetic interference and bus modulation, enabling hardware-free radio transmission for data exfiltration, covert channels, or custom audio broadcasting. The system bus modulation utility modulates data onto a carrier wave by controlling the timing of memory bus operations, functioning as a complete software-defined radio transmitter without dedicated hardware.