SigDigger is a free digital signal analyser built for picking apart radio transmissions you know nothing about. It is the work of Gonzalo José Carracedo Carballal, a Madrid-based developer who goes by BatchDrake on GitHub and by the call sign EA1IYR on the amateur bands. The first pre-releases appeared in 2019. Late in 2025 the project switched licence, and according to the licence file in the repository it is now distributed under the LGPL v3.
What SigDigger is for
Anyone who has used Gqrx will recognise the layout straight away. The author says he deliberately borrowed that receiver’s arrangement, and even its spectrum display, to keep the learning curve short. The similarity ends at the screen. Gqrx is built on GNU Radio, whereas SigDigger is a Qt front end for Suscan, a signal processing library by the same author, itself built on another of his libraries called Sigutils. The two processing chains share nothing.
Work starts on the spectrum and waterfall, where you spot an unfamiliar signal. You then open an inspector on that channel, and the program demodulates frequency-shift (FSK), phase-shift (PSK) or amplitude-shift (ASK) keyed signals in real time, with parameters you tweak until the constellation settles and the symbols become readable. SigDigger can also decode analogue video, examine bursty transmissions and play back analogue voice channels. The input is either a radio connected to the computer, meaning any model the SoapySDR library supports, or a previously recorded sample file.
Plugins widen the scope. The author singles out AmateurDSN for its versatility and also publishes APTPlugin, AntSDRPlugin and ZeroMQPlugin, whose names give away their purpose: APT weather satellite images, AntSDR radios and data streaming over ZeroMQ. Compared with Inspectrum, another signal analysis tool, the split is clear. Inspectrum dissects recordings, SigDigger also works on the live signal, and the two make a good pair.
Who is it for?
SigDigger is aimed at radio amateurs, listeners trying to identify a mystery transmission, security researchers studying proprietary radio protocols and people teaching signal processing. A PDF user manual in the repository’s doc folder is a sensible place to start.
Be prepared for a one-person project, though. The latest stable release, 0.3.0, came out in July 2022. Since then new features have shipped as development builds, the most recent from April 2025, while the code kept moving on GitHub until February 2026. On Windows the author admits he cannot guarantee complete, reproducible builds, and the macOS package is put together on request. Modulation and symbol rate are treated as familiar concepts. For casual listening to FM broadcasts or airband traffic, a receiver like Gqrx is more straightforward. And for controlling a USRP or bladeRF radio from your own code, UHD and libbladeRF are the tools to look at.
Download SigDigger safely
Everything goes through the BatchDrake/SigDigger repository on GitHub. Its releases page offers a self-contained AppImage for x86-64 Linux, about 107 MB, that runs without installation, plus a Windows ZIP archive in the development build. Version 0.3.0 is also available as a DMG image for Intel-based Macs. Linux users can alternatively run blsd, a script hosted on the author’s site actinid.org that builds SigDigger and the chosen plugins in a local folder without touching the rest of the system.
The software is completely free, with no paid edition or strings attached. Its dependencies, Sigutils, Suscan and SuWidgets, are published on the same GitHub account, which is where to fetch them for a manual build. An AppImage or Windows archive floating around a file-sharing site under some other name comes with no proof of origin and could contain something other than the program.
Frequently asked questions
Is SigDigger still maintained?
Yes, at a modest pace. The repository received changes until February 2026, including the move to the LGPL in late 2025, and the latest development build is from April 2025. No new stable release has appeared since 0.3.0 in 2022, however.
Which radios does SigDigger support?
Any radio with a SoapySDR module, since that abstraction library is how it reaches the hardware. The exact list therefore depends on the modules installed on your machine. It can also work without a radio, on recorded sample files.
Is SigDigger free?
Yes. It is released under the LGPL v3 and can be downloaded at no cost from GitHub. Neither the program nor its plugins have any paid option.
