A cart has at least three wheels. It has one or more loop antennas, and a radio transceiver connected with the antennas. The antennas and transceiver operate at a frequency lower than 1 megahertz. The loop antennas are each at least 0.2 square meters in area. The cart is moved to an area such as a room, and the transceiver communicates with various RF tags in the room. Because of the antenna configuration, the portion of spectrum employed, and the power levels used, the cart is able to communicate with most if not all of the RF tags in the room. The cart can then be moved to another area such as another room, and the process repeated. In this way an inventory of tags can be made without expensive permanently installed infrastructure. The system is robust against interferers such as large metal objects and intervening objects.