GNU Radio is a free & open-source software development toolkit
that provides signal processing blocks to implement software radios.
It can be used with readily-available low-cost external RF hardware
to create software-defined radios, or without hardware in a
simulation-like environment. It is widely used in hobbyist, academic
and commercial environments to support both wireless communications
research and real-world radio systems.

uhd, cppunit, gsl, lxml, numpy, orc, qwt, wxPython and Sphinx
(this last to generate additional docs) are optional dependencies.