An emissions detection apparatus for at least one of detecting, identifying, diagnosing and geolocating an electronic device or an information transmitted from the electronic device includes an emissions collections device connected to an antenna receiving emission of an electromagnetic energy emitted from the electronic device and collecting a spectral data emitted from the electronic device; one or more algorithms processing the collected spectral data, algorithms selected from a group consisting of a peak detection algorithm, a multiple peak detection algorithm, a harmonic correlation algorithm, a non-harmonic correlation algorithm, a time correlation algorithm, a phase correlation algorithm, and a duty cycle timing correlation algorithm; and one or more algorithms matching the processed spectral data to an emissions template, wherein a match of the processed spectral data with the emissions template at least one of detects, identifies, diagnoses and geolocates the electronic device or the information transmitted from the electronic device.