This antenna adaptor (840) is intended to be placed between an antenna (830) and a receiving channel (850). It includes: a first conductive wire (806) crossed by an external current (iext) corresponding to a signal delivered at the output of the antenna, the first wire generating in its vicinity an external magnetic field; and a magnetometric sensor (810), placed in the vicinity of the first conductive wire, sensitive to a flow of the external magnetic field and able to generate an output signal corresponding to the external current.