SDR# is described as '(SDRSharp) is a popular, simple, fast and extensible Software Defined Radio program written from scratch in C# to experiment new Digital Signal Processing techniques and push the Microsoft .NET Framework to its limits' and is an app. There are more than 10 alternatives to SDR# for Linux, Windows, Mac and Android. The best alternative is CubicSDR, which is both free and Open Source. Other great apps like SDR# are GNU Radio, Gqrx, SDRangel and inspectrum.
Gqrx is a software defined radio receiver powered by the GNU Radio SDR framework and the Qt graphical toolkit. It supports many of the SDR hardware available, including Funcube Dongles, rtl-sdr, HackRF and USRP devices.
A graphical application for showing the Fast Fourier Transformation (FFT) as graph and waterfall diagram of the radio spectrum retrieved by Software Defined Radio (SDR) devices supported by GrOsmoSDR. Plugins enable demodulating a selected signal.
HDSDR is a freeware Software Defined Radio (SDR) program for Microsoft Windows 2000/XP/Vista/7/8/8.1/10. Typical applications are Radio listening, Ham Radio, SWL, Radio Astronomy, NDB-hunting and Spectrum analysis.