Systems and methods for detecting radio frequency (“RF”) signals and corresponding origination locations are disclosed. An RF sensor device includes a software-defined radio and an antenna pair for receiving RF signals. Furthermore the RF sensor device may include a processing unit for processing/analyzing the RF signals, or the processing unit may be remote. The system calculates a phase difference between an RF signal received at two separate antennas of an antenna pair. The phase difference, the distance between the antennas, and the frequency of the RF signal are used for determining the origination direction of the RF signal. In various embodiments, the origination direction may indicate the location of a UAV controller or base station. The software-defined radio may include more than one antenna pair, connected to multiplexers, for efficiently scanning different frequencies by alternating active antenna pairs. Moreover, the system may execute packet-based processing on the RF signal data.