To assist an operator to position a wireless camera so that a base station receives with good quality a radiofrequency signal transmitted from a transmitter linked to the camera, several measurers linked to diversity receivers of the signal each determine whether a characteristic of the signal via the respective receiver satisfies a reception criterion. In the base station, a counter counts the receivers satisfying the reception criterion, and a divider establishes a reception quality indicator dependent on the number of satisfactory receivers so as in particular to retransmit it via a return channel to the camera so that it can be displayed thereon.