Abstract: There is disclosed an apparatus for measuring the strength of an electromagnetic field. The apparatus comprises a plurality of antennas arranged such that the field is received from all directions, each antenna supplying an RF signal as output. The apparatus also comprises a plurality of transforming modules, each of said modules being fed with the RF signal supplied by one of the antennas, each of said modules transforming the impedance of the RF signal it receives as input, so as to supply another RF signal as output. The apparatus also comprises a plurality of converting modules, each of said modules being fed with the RF signal supplied by one of the transforming modules, each of said modules converting the RF signal it receives as input into a DC current it supplies as output, said DC current varying substantially as a logarithmic function of the said RF signal.