To optimize performance in a small form factor the Track Box Passive contains 2 antennas internally, TX (transmit) and RX (receive). The TX antenna is located in the lower half of the box and the RX is in the upper half, each antenna needs a clear line of sight to transponders in order to receive passings.
The below diagrams show the shape of the antenna field, the inner line represents expected 99% read rate at 4m from the front of the antenna, the outer line shows the 8m line with 90% expected read rate (with a single box).
Side View
Top View
