We present a cognitive spectrum access solution for FH-CDMA ad hoc networks. Building on a cluster-based split phase multi-channel MAC protocol, we propose a mechanism for local interference avoidance through distributed hopset adaptation. Its goal is to identify and substitute channels not suitable for reliable communication. Substitution rules replace channels by locally unused hopsets. This way, interference is mitigated while maintaining orthogonality between nodes’ hopsets. We evaluate the gains of the proposed method with a simplified system model.