Today, cellular networks have saturated frequencies below 3 GHz. Because of increasing capacity requirements, 5th generation (5G) mobile networks target the 3.5 GHz band (3.4 to 3.8 GHz). Despite its expected wide usage, there is little empirical path loss data and mobile radio network planning experience for the 3.5 GHz band available. This paper presents the results of rural, suburban, and urban measurement campaigns using a pre-standard 5G prototype testbed operating at 3.5 GHz, with outdoor as well as outdoor-to-indoor scenarios. Based on the measurement results, path loss models are evaluated, which are essential for network planning.