Nowadays, a wide variety of terminals are proposed to nomadic users. Generally these terminals provide wireless communication operating at frequencies between one and a few GHz. For technical reasons, including multiple access to the communication channel and battery autonomy, these terminals transmit only during very short periods i.e. transmission bursts. For a direct observation of certain characteristics of the transmitted signals radiated by such terminals, only a few measurement setups exist. This article proposes such a novel real-time 3D electromagnetic field measurement instrument with direct visualization. The prototype used for validation is based on an array of probes regularly attached on a non-conductive rigid loop which is put into fast rotation around the terminal under test. To cite this article: J. Rioult et al., C. R. Physique 10 (2009). (C) 2008 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.