This paper presents the implementation and test of a low cost Software Defined Radio based on the Raspberry Pi2 computer, the RTL-SDR dongle radio receiver, and the GNU Radio software. Key aspects regarding installation and configuration of GNU radio and RTL-SDR drivers on Raspbian Operating System are addressed. The resulting device can demodulate AM and FM signals in the frequency range from 30MHz to 1.7GHz and also can meet the function of Spectrum Analyzer in moderate sensitivity demanding applications.