A software-defined radio system, or SDR, is a radio communication system where components that have been typically implemented in hardware (e.g. mixers, filter, amplifiers, modulators/demodulators, detectors, etc.) are instead implemented by means of software on a personal computer or embedded computing device [1]. There are some major advantages of the SDR over traditional radio systems for a satellite communication. The ability to modify the functionality of satellite’s radio system remotely is very important as the satellite is not available for any physical modifications after it is launched. With a SDR system on board, the functionality of a satellite’s communication channel can be effectively modified and updated (including changes in modulation, frequency, data rate, protocol, etc.) Several practical examples are demonstrated where a single Universal Software Radio Peripheral (USRP) hardware unit and the GNU radio software toolkit are used for different radio applications (e.g. collecting of AIS data messages, receiving NOAA APT satellite images).