The pilot of Boeing Stearman A75N1, N56270, reported that his VHF radio had a malfunctioning frequency selector which necessitated manually setting the Medford Tower frequency prior to taxiing. This problem prevented him from selecting other frequencies. He called the control tower while he was taxiing, just after passing a Cessna 150. He reported that at that time, he was looking out his right side to assure clearance from parked aircraft. He also stated that Taylorcraft, N95078, had rounded a corner beyond the nose of his aircraft and was approaching on his left, but he did not see the Taylorcraft until they collided. At 1054:50, ground control had advised N95078 of the oncoming Stearman, and N95078 had steered right to provide clearance. The Stearman pilot made his first call to the tower at 1055. Shortly thereafter, the Taylorcraft pilot noted the planes converging and turned to avoid a collision. However, the left wing of each struck one another. N95078 was substantially damaged.