Aether SDR

A simple FM radio receiver for the RTL-SDR dongle, written in C++17.

This is a hobby project I created to learn more about C++, multithreading, and Digital Signal Processing (DSP). It implements a basic demodulator directly on top of the librtlsdr driver, without relying on large frameworks like GNU Radio.

Architecture

The application uses a Forked Producer-Consumer architecture to separate the hardware reading from the signal processing:

• Producer Thread: Reads raw IQ samples from the RTL-SDR dongle via USB. It pushes data to two separate queues:
  • Audio Queue: Blocking. If full, the producer waits to ensure no audio samples are lost.
  • GUI Queue: Non-blocking. If full, packets are dropped to ensure the visualization never stalls the audio.
• Audio Callback (Consumer): Managed by miniaudio. It wakes up periodically to demodulate data and fill the system audio buffer in real-time.
• Visualizer (Consumer): Uses Raylib and Raygui to render the raw signal data and a real-time FFT spectrum.

Features

• Spectral Analysis: Real-time FFT magnitude visualisation using fftw3.
• Interactive UI: A volume slider that dynamically scales both audio output and time-domain visualization.

Dependencies

• librtlsdr (Driver for the USB dongle)
• libraylib-dev (Graphics library for the visualizer)
• fftw3 (C library for computing discrete Fourier transforms)
• miniaudio (Included as a single-header library)
• C++17 compliant compiler (GCC/Clang)

Building

make

Running

The program opens a GUI window displaying the raw signal, the frequency spectrum, and outputs audio to the default device.

# Sample rate set to 1.92 MHz, frequency 95.7 MHz, gain 40 dB
./aether-sdr -s 1.92 -f 95.7 -g 40
# Defaults are 1.92 MHz, 98.4 MHz and 35 dB
./aether-sdr

License

MIT