RFID transponders range in size from the size of a grain of pepper to the size of a brick. The size depends on whether the tag uses a battery to broadcast a signal or simply reflects a signal back from the reader. The other factor is the size of the antenna. As the antenna gets smaller the read range decreases. Tags that are the size of a grain of pepper have an antenna etched onto the microchip. Because the antenna is so small, the tags can only be read from less than an inch away.
