In cognitive radio networks, a premise for two nodes to communicate with each other is that they have a rendezvous which means they switch to the same channel at the same time. A common mechanism to achieve rendezvous is applying channel hopping. Most existing channel hopping protocols operate in a single-radio environment and evenly use all the available channels. Utilizing only a single radio limits the rendezvous probability between nodes while without considering the time-varied channel conditions of different channels results in inefficient channel allocations. To solve the rendezvous problem efficiently, in this paper, we propose an Adjustable Multi-radio Channel Hopping (AMCH) protocol that operates in a multi-radio CRN. Instead of evenly using available channels, AMCH enables a node to adjust the ratio of using different channels. Simulation results verify that such a ratio adjustable channel hopping scheme provides an efficient way to solve the rendezvous problem.