The simple tone sense (STS) protocol is designed for multihops PRNs (packet radio networks) with multiple directional antenna stations. The protocol can minimize transmission interference by using a group of tones to identify the active neighbors. A variation of the STS protocol, the variable power tone sense (VPTS) protocol, is also designed to further reduce interference. Algorithms for assigning tones and for determining the orientation and broadcasting angles of the directional antennas are designed. Design examples are given. Simulation shows that the STS protocol performs better than the BTMA (busy tone multiple access) protocol, especially when the traffic is heavy. VPTS, however gives still better throughput performance.< >