Base and cover elements of a food container can be rapidly closed at a plant and can be easily opened and closed by a customer. Internal andor external anchor tabs may also be selectively interleaved with the dielectric layers. Aerodynamically shaping antenna structure to enclose an antenna element grid provides additional antenna structure volume, which is efficiently utilized by locating antenna support equipment within the antenna structure. The sensor receiving passage is adapted to position the sensor such that the sensing element is unreachable by a linear path from the outer surface through any opening in the main body.