fldigi

fldigi is a digital modem application for amateur radio that supports a wide range of digital modes. It runs on macOS, Linux, Unix and Windows, and provides tools for encoding, decoding, and visualizing signals, including waterfall displays and audio monitoring. The software is distributed as source, DMG and Windows installers, with build instructions available on its wiki.

The suite includes complementary utilities such as flmsg for NBEMS messaging, flrig for rig control, flamp for file transfer, and flwrap for file encapsulation and compression. Additional programs handle tasks like voice net control, DX cluster access, antenna analyzer control, and test suites for simulation and performance verification.

fldigi is maintained by W1HKJ and associates, with regular releases and documentation in multiple languages. It is positioned for ham‑radio operators who need a stable, open‑source solution for digital communications and related ancillary functions.