What is an IQ file and how can I use it?

Is there a difference between an IQ file and a WAV file? When I record in iq mode, it saves a file named ....iq.wav, which gives me the impression that this is an iq file in a .WAV format. I want to use some third party software to extract information from this file, particularly the modulation index.

Using GNURadio and the information at https://charlesreid1.com/wiki/Gnuradio/Wav_to_Waterfall, I can listen to the WAV File Source and I can see the waterfall displayed. My diagram looks like this:

However, can I also do things like display the carrier wave and ultimately measure the modulation index given this wav file?


  • IQ refers to the type of signal data contained within the file. A wave file is one of many file formats that contains meta information about the data within it, like sample rate, number of channels, etc. So the wave file meta information is "wrapped around" the IQ data resulting in a file that is mostly self-contained, i.e. you can hand it to GNURadio and it will know, mostly, what to do with it.

    I don't know GNURadio myself, but I think your diagram above is missing an AM demodulator before the mod index block. So change that second path going to the audio sink block with one that looks like:
    --(IQ data)--> AM demod --(real-mode data)--> mod index --> audio sink
  • I have decoded AM with something this simple
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