A bi-directional radio monitoring system includes a base unit (14) having a base RF transceiver (15) with two or more fixed antennae (17, 18, 19) associated therewith. The base unit communicates with a portable transceiver (16) using ultra high frequency (UHF) radio signals whereby, by using the two or more antennae (17, 18, 19), the base unit (14) is able to determine a relative position of the portable transceiver (16), depending on the closeness of the movable transceiver (16) to each of the fixed transceiver antennae (17, 18, 19). The RF signal transmission by the base unit (14) may vary in terms of channel, power, packet length, data rate and packet contents transmitted from each antennae (17, 18, 19) to give rise to responses from the portable transceiver (16) that enable the base unit (14) to track the movement of the portable transceiver (16).
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