Telecommunications have been in constant evolution during past decades. Among the technological innovations, the use of digital technologies is very relevant. Digital communication systems have proven their efficiency and brought a new element in the chain of signal transmitting and receiving, the digital processor. This device offers to new radio equipments the flexibility of a programmable system. Nowadays, the behavior of a communication system can be modified by simply changing its software. This gave rising to a new radio model called Software Defined Radio (or Software-Defined Radio - SDR). In this new model, one moves to the software the task to set radio behavior, leaving to hardware only the implementation of RF front-end. Thus, the radio is no longer static, defined by their circuits and becomes a dynamic element, which may change their operating characteristics, such as bandwidth, modulation, coding rate, even modified during runtime according to software configuration. This article aims to present the use of GNU Radio software, an open-source solution for SDR specific applications, as a tool for development configurable digital radio. © 2005 IEEE.10111561161The Wireless Innovation Forum, , http://www.wirelessinnovation.orgLackey, R.J., Upmal, D.W., Speakeasy: The military software radio (1995) IEEE Communications Magazine, , MayNguyen, M., (2003) Software Radio (R) Evolution and Its Application to Aeronautical Mobile Communications, pp. 19-22. , MayMitola, J., Software radios-survey, critical evaluation and future directions (1992) IEEE National Telesystems Conference, pp. 13/15-13/23. , MayMitola, J., Cognitive radio: Making software radios more personal (1999) IEEE Personal Communications, , AugScaperoth, D., (2006) Cognitive Radio Platform Development for Interoperability Military Communications ConferenceCowling, S., Hands-on software defined radio (2008) Dayton Hamvention SDR ForumEttus, M., Universal Software Radio Peripheral, , http://www.ettus.comBlossom, E., How to Write A Signal Processing Block, , http://www.gnu.org/software/gnuradio/doc/howto-write-a-block.htmlBlossom, E., Exploring GNU Radio, , http://www.gnu.org/software/gnuradio/doc/exploring-gnuradio.htmlKaszuba, A., MIMO implementation with alamouti coding using USRP2 (2011) Progress in Electromagnetics Research Symposium ProceedingsThe OpenBTSProjet, , http://openbts.sourceforge.netSpill, D., BlueSniff: Eve meets alice and bluetooth (2007) WOOT '07 Proceedings of the First USENIX Workshop on Offensive TechnologiesPinomaa, A., Utilization of software-defined radio in power line communication between motor and frequency converter (2010) IEEE International Symposium on Power Line Communications and Its Applications (ISPLC)The FlexRadio, , http://www.flex-radio.com, FLEX-5000A™ Software Defined Radio