SigDigger: A Graphical Digital Signal Analyzer for Linux

Recently a new open source Linux based SDR application called SigDigger was released by programmer BatchDrake (Gonzalo J. Carracedo). It is based on his own DSP libraries called Sigutils and Suscan which can take advantage of multi-core CPUs. SigDigger also makes use of the SoapySDR interface, so it is compatible with almost all software defined radios including the RTL-SDR.

SigDigger Screenshot
SigDigger Screenshot

Like other general purpose SDR applications, SigDigger has your typical AM/FM/LSB/USB demodulation and audio playback features. However, it also has some key additional features that make it worth taking a look at if you're interested in reverse engineering, or taking a closer look at digital signals. The features include:

  • Both realtime and replay analysis modes
  • Analog audio playback (AM, FM, LSB and USB)
  • Baseband recording (full spectrum and per-channel)
  • Per-device gain presents
  • Dynamic spectrum browsing
  • ASK, FSK and PSK inspection
  • Gradient-descent SNR calculation
  • Different spectrum sources (cyclostarionary analysis, signal power…)
  • Symbol recording and visualization
  • Transition analysis

Planned features already implemented and just waiting to be exposed to the UI:

  • Parameter estimation (baudrate, constellation order…)
  • Fast symbol autocorrelation analysis
  • Automatic calculation of scrambling polynomials
  • Symbol stream codecs

Possible future features coming soon:

  • Symbol tagging (correspondence between symbols and groups of bits)
  • Automatic symbol tagging guessing
  • Automatic convolutional code detection
  • Viterbi decoding

We note that while the UI looks like GQRX, it is not based on GQRX at all. Rather BatchDrake just liked the minimal UI of GQRX. Also unlike GQRX, SigDigger is not based on GNU Radio, so it may be a bit more efficient and lightweight.

Below we've embedded a video that BatchDrake uploaded his YouTube channel which demonstrates SigDigger being used to inspect a PSK channel.

Using SigDigger to inspect a PSK channel

This software looks great, and we think it deserves some serious attention and testing, so check it out on the GitHub. Binary releases are also available, although BatchDrake notes that they are minimally tested, for x64 Linux only, and preferably for Debian-like distros. Alternatively, it can be installed from source, after installing the Sigutils and Suscan DSP library dependencies.

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