A variety of continuous wave, swept frequency, and pulse transmission experiments were conducted in and around the Wawona Tunnel at Yosemite National Park. The experiments were performed to obtain data on the HF electrical properties of large volumes of rock. The experiments involved the propagation of electromagnetic waves through more than 300 m (1000 ft) of granite. In situ bulk conductivities of 2–5 × 10−4 mho/m and relative dielectric constants of 5–7 were measured in the 3–50 Hz band. Experimental errors in these values are estimated to be less than ±9% and ±10%, respectively.