Due to interferences from pervasive electromagnetic emissions, the likelihood of irregular performance and possibly loss of control of an unmanned aircraft system (UAS) grows as small commercial drones are deployed in more applications. The UAS electromagnetic compatibility has therefore become a crucial factor to consider in UAS design and operation to minimize any potential safety issues. A UAS may experience radio frequency interference (RFI), a subset of a broader range of electromagnetic interference (EMI), through its communication link or capacitive coupling of the RF electrical field. We conducted measurements both outside and within a chamber to assess the impacts of front-door and back-door RFI on the C2 (command and control) link and the subsystem components of two distinct drone models. In this paper, we describe the measurement setup and procedures, present the results, and analyze the safe distances of the drones from RFI sources such as cellphone base stations and airport surveillance radar (ASR) under the impacts from these two types of RFI in this study.