a frame;

a generally planar conveyor that is disposed movably on the frame and that conveys items through a path of travel, each item having at least one respective radio frequency identification tag disposed thereon;

a first antenna disposed proximate the path of travel so that the first antenna

radiates a first gain pattern carrying radio frequency signals into a first area through which the items pass, wherein the first gain pattern defines an electric field having magnitude and direction, and

receives responses to the radio frequency signals from radio frequency identification tags on the items in the path of travel;

a second antenna proximate the first antenna and the path of travel so that the second antenna

radiates a second gain pattern carrying radio frequency signals into the first area, wherein the second gain pattern defines an electric field having magnitude and direction;

at least one radio frequency receiver that receives signals from the first antenna corresponding to the responses received by the first antenna from the respective radio frequency identification tags and outputs first signals corresponding to the responses; and

a processor that receives the first signals from the at least one receiver and is programmed to associate a said first signal with a first said item if the processor receives the first signal from the at least one receiver while at least a portion of the first item is within a predetermined second area that includes at least part of the first area,

wherein the first gain pattern and the second gain pattern are defined, and wherein the second antenna is disposed with respect to the first antenna, so that the direction of the electric field of the first gain pattern opposes the direction of the electric field of the second gain pattern in a direction generally perpendicular to the plane of the conveyor in the first area and in a direction generally parallel to the path of travel in the first area.