Global Navigation Satellite Systems (GNSS) have become a necessity for modern society. The positioning, navigation, and timing services provided by GNSS have vast applications used by financial markets, autonomous vehicles, communications networks, power grids, mail systems, and far more. The advancement of receiver technology has even allowed for easy use for the smartphone user, likely creating billions of GNSS users daily. For these reasons, the US Department of Homeland Security lists the Global Positioning System (GPS) as a critical infrastructure, indicating that 〜its incapacitation or destruction would have a debilitating effect on security, national economic security, national public health or safety, or any combination there of. Despite this, GPS signals are easily interfered with. In fact, Radio Frequency Interference (RFI) on GNSS bands such as jamming and spoofing is becoming increasingly common. While RFI does not impact the entire system and only affects users in a relatively small area, it can be catastrophic to many users. Therefore, it is important to have a way to prevent jamming and spoofing, requiring a method of localizing the source of the RFI. One of the simplest methods of localization is power difference of arrival (PDOA). PDOA localization estimates the RFI source location by looking at the difference in power for several receivers spread out in an area near the RFI source for the GNSS band of interest. This can be done using data from commercial-off-theshelf receivers which do not always report power in dB. This requires characterizing the receiver in order to understand the relationship between the input power on the antenna and the automatic gain control (AGC) output metric as there is no standard for such a measurement. A UBlox ZED F9P receiver was used in this paper. Characterization was performed, ultimately allowing for a PDOA localization to be performed. This demonstrated that the receiver is a powerful, low-cost tool for RFI detection, characterization, and localization.