A simple Nyquist effect plugin to convert I/Q (in-phase and quadrature) signals to Amplitude/Phase (AM decode radio signals). Analyse and decode On-Off-Keying (OOK) / Amplitude-Shift-Keying (ASK) signals recorded by e.g. RTL-SDR software with Audacity.

Example conversion in Audacity

When analyzing radio signals I always like to load recorded samples into Audacity to visualize and find pattern. This involves transforming the signals with some python scripts and then loading the outputs many times. I’m about to convert some of those scripts to Audacity plugins and here is the first simple Nyquist plugin to convert I/Q signals to Amplitude/Phase (AM decode). This helps me with decoding On-Off-Keying (OOK) / Amplitude-Shift-Keying (ASK) signals.

Installing

Fetch from GitHub source and see What Effect, Generator and Analyzer plug-ins does Audacity support and how do I install them?

I.e. get Convert-IQ-Aphi.ny and copy to Audacity’s Plug-Ins folder.

  • on 32-bit Windows Program Files/Audacity
  • on 64-bit Windows Program Files (x86)/Audacity
  • On Mac OS X/macOS ~/Library/Application Support/audacity/Plug-Ins
  • on Linux ~/.audacity-files/plug-ins

Then use Effect, Generate or Analyze Menu > Add / Remove Plug-ins to select and enable the plug-in.