An apparatus for reading multiple RFID codes carried by articles in a group, the apparatus comprising: an RF code reader including interrogation and response detection antennas directed inwardly into a shielding enclosure configured to concentrate RF signals in a reading zone, with controls for applying an RF charging signal in at least one predetermined frequency band and discerning RFID codes from responsive signals received from tagged articles in the group, wherein at least one passage is provided through the shielding enclosure, through which the articles are movable between the reading zone and an area outside of the shielding enclosure, the at least one passage extending through a vestibule leading into and/or out of the reading zone, the vestibule being configured to attenuate reflected electromagnetic energy in the predetermined frequency band and comprising electromagnetic damping structures, wherein the shielding enclosure comprises at least two opposite electrically conductive walls (2, 3) each with at least one surface facing the passage, wherein at the reading zone, the electrically conductive walls (2, 3) are configured to homogeneously distribute RF energy over the articles in the reading zone, wherein at the vestibule, the surfaces of the electrically conductive walls (2, 3) facing the passage carry the electromagnetic damping structures for attenuating electromagnetic energy at least in the predetermined frequency band so as to limit effective interaction with any stray RFID tagged articles outside the shielding enclosure, wherein the electrically conductive walls (2, 3) define lengths extending along two opposite sidewalls of the vestibule, characterized in that the electrically conductive walls include focusing portions at the reading zone defining two clamshell shapes on two opposite sidewalls of the vestibule, wherein each of the two clamshell shapes is formed by five wall portions of the electrically conductive walls (2, 3), wherein five antennas are respectively mounted on the five wall portions, the five antennas being directed inwardly toward the reading zone, and the clamshell shaped wall portions of the electrically conductive walls (2, 3) form clamshell reflective structures around the antennas, the clamshell reflective structures being configured not only to focus signal strength on the reading zone but also to elongate propagation paths of the RF signals that are reflected transversely and finally obliquely across the reading zone. an RF code reader including interrogation and response detection antennas directed inwardly into a shielding enclosure configured to concentrate RF signals in a reading zone, with controls for applying an RF charging signal in at least one predetermined frequency band and discerning RFID codes from responsive signals received from tagged articles in the group, wherein at least one passage is provided through the shielding enclosure, through which the articles are movable between the reading zone and an area outside of the shielding enclosure, the at least one passage extending through a vestibule leading into and/or out of the reading zone, the vestibule being configured to attenuate reflected electromagnetic energy in the predetermined frequency band and comprising electromagnetic damping structures, wherein the shielding enclosure comprises at least two opposite electrically conductive walls (2, 3) each with at least one surface facing the passage, wherein at the reading zone, the electrically conductive walls (2, 3) are configured to homogeneously distribute RF energy over the articles in the reading zone, wherein at the vestibule, the surfaces of the electrically conductive walls (2, 3) facing the passage carry the electromagnetic damping structures for attenuating electromagnetic energy at least in the predetermined frequency band so as to limit effective interaction with any stray RFID tagged articles outside the shielding enclosure, wherein the electrically conductive walls (2, 3) define lengths extending along two opposite sidewalls of the vestibule, characterized in that the electrically conductive walls include focusing portions at the reading zone defining two clamshell shapes on two opposite sidewalls of the vestibule, wherein each of the two clamshell shapes is formed by five wall portions of the electrically conductive walls (2, 3), wherein five antennas are respectively mounted on the five wall portions, the five antennas being directed inwardly toward the reading zone, and the clamshell shaped wall portions of the electrically conductive walls (2, 3) form clamshell reflective structures around the antennas, the clamshell reflective structures being configured not only to focus signal strength on the reading zone but also to elongate propagation paths of the RF signals that are reflected transversely and finally obliquely across the reading zone.