SigDigger - A free digital signal analyzer

SigDigger is a Qt5 digital signal analyzer written in C/C++ that runs in GNU/Linux, macOS and Windows. Unlike existing alternatives, SigDigger is not based on GNU Radio. Instead, it uses its own DSP library (sigutils) and a realtime signal analysis library (Suscan) that exploits multicore CPUs to distribute load. Also, SigDigger supports most SDR devices in the market thanks to SoapySDR. Sigutils, Suscan and SigDigger are software libre, licensed under the terms of the General Public License version 3.

System requirements

SigDigger works in x86-64 CPUs running GNU/Linux, MacOS and Windows. Support for additional architectures is on its way. An OpenGL-capable videocard, while not strictly necessary, can improve GUI performance considerably.

Downloading or building SigDigger

You can find build instructions in the official GitHub repository. You can also speed up the process executing the BLSD script. Pre-compiled binary releases are also available here.

Development builds

Thanks to GitHub Actions, we now support continuous integration and development releases. These releases are somewhat less tested than official releases, but they are full of new and cool features, and are generally up to date:

• Windows (x86-64) redistributable ZIP archive
• MacOS (x86-64) DMG file (reported to work in M1 machines too with Rosetta 2)
• GNU/Linux (x86-64) executable AppImage

Current features

• GNU/Linux, macOS and Windows support
• OpenGL-enhanced spectrum and waterfall
• Both realtime and replay analysis modes
• Analog mono 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
• Doppler analysis
• Filename-based raw file parameter guessing
• Transition analysis
• Interactive Panoramic Spectrum view
• Waveform inspection window, including burst detection and limited off-line demodulation support
• Signal source decimation
• Bandplan information
• Audio channel recorder
• Blind parameter estimation
• Network broadcast of demodulated channel data
• UDP broadcast of received samples and demodulated symbols
• Spectrum integrator (for radioastronomy enthusiasts like me!)
• Fast symbol autocorrelation analysis
• Analog TV demodulation
• SGDP4-based frequency correction (by means of TLE files)
• Subcarrier inspection

Planned features

The following features are present in the Suscan core, but their exposition to the UI is in progress:

• Automatic calculation of scrambling polynomials
• Symbol stream codecs

The following features have been presented in one of my talks, but they are not implemented neither in Suscan nor in SigDigger (yet):

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

The following features are in an optimistic TODO, but they wil hopefully be part of SigDigger some day in the future:

• Make it available in the official repositories of some mainstream GNU/Linux distro (on its way!)
• OFDM inspector
• DSSS inspector
• Internationalization
• Turbocode / LDPC code support
• Bult-in decoder / demodulator tabs
• Python integration

Documentation

This is work in progress, and some help will also be appreciated (see below).

Your software is cool, how could I help you?

The easiest and most useful thing you can do is to use it, distribute it, talk about it! Try it with different devices and configurations, force its limits, break it. All feedback will guide my effort into something that is useful for everyone.

If you find SigDigger useful and miss some documentation on the software, that’s another way you can help. I’ll make it available in this website.

If you are a programmer and you want to help, I would be happy to explain the internals to you and guide you along the process. You can also provide patches, improvements and bugfixes in the form of pull requests in GitHub.

If you are good with languages and would like to do some translation work on SigDigger, you are welcome as well! As none of SigDigger components are internationalized yet, it will take me some to give you a list of strings you can translate. But if you are truly willing to do this, I will not mind prioritizing this before other tasks.

All help, of any kind, will be duly noted in the credits window.

Acknowledgements

The latest UX improvements and MacOS X support have been possible thanks to the invaluable help of Mehdi Asgari. Windows support was finally possible thanks to Ángel Ruiz Fernández.

Partial transcription of the spanish national frequency allocation table (CNAF) has also been possible thanks to Shiki Owo.

Contact

You cand send me an e-mail or reach me on Twitter. There is also a Discord server you can join if you prefer a more interactive communication.