 Human activities generate a great deal of radio energy, as in communications, navigation, and entertainment applications.Some of these sources provide enough energy such that their reflection or transillumination can enable passive covert radar (PSR) MASINT, which is also called passive coherent location (PCL).A foreign transmitter, preferably a purpose-built radar transmitter such as used in air traffic control, but really any powerful transmitted such as TV or FM, potentially can produce reflected signals that do not return to the designated receiver of the foreign radar operator.