SDR with HackRF One (Lesson 11: Replay)

Lesson 11 Overview

  • Being a good neighbor on the spectrum
  • QT vs. WX GUI in GNU Radio
  • Saving a waveform to file
  • Inspectrum
  • Transmitting
  • Replaying a captured radio signal
  • Using multiple HackRF Ones

In order to clearly see my screen during the demonstrations, viewing the video in full screen mode may help. Even better: You can download this video in high resolution (720p). (torrent)


  1. Capture a radio signal and save it to a file with hackrf_transfer ( Hint: use the -r option).
  2. Convert the file from unsigned 8-bit integers to 32-bit floats. This can be done with:
    sox foo.s8 foo.f32


    cat foo.s8 | csdr convert_s8_f > foo.cfile

    or with convert_s8_cfile.grc.

  3. Analyze the file with GNU Radio Companion and/or inspectrum to verify that you captured your signal of interest.
  4. Determine how many distinct sample values are present in your signal. (Hint: The number should be no more than 256.)
  5. How many bits of dynamic range does your signal span. (Hint: take the base 2 logarithm of the number of distinct sample values.)


Leave a Reply