A portable radio communication device D′ with adjustable total gain and an associated gain adjustment method via a conductive metal frame C situated at the periphery of the portable device D′. For this purpose, the frame C includes several metal sections P1, P2, P3, P4 not connected to each other and separated from each other by openings F1, F2, F3, F4. Switching elements S1, S2, S3, S4 make it possible to electrically connect two consecutive sections in such a way as to modify the length of the sections and to modify the electromagnetic coupling between the antenna A and the metal frame C. The modification of coupling causes a modification of the value of the resultant gain Gr of the antenna A. A calibration step makes it possible to select the sections to be connected together in order to obtain the desired resultant gain Gr of the antenna A.