An external primary spectrum user detector (ESUD) is used to take over the role of integral radar detectors, and relieve user devices of the constraints associated with Primary Spectrum User detection. The ESUD can establish a relationship with the user devices by means of a cryptographic signature. The ESUD installation includes assigning it a frequency band to scan for primary spectrum user signals and the type of signals to be detected. Once activated, the ESUD will scan its assigned frequencies and emit to types of messages, ''All Clear'' and ''Primary Spectrum User detected.'' User devices on the network listen for the ESUD messages. In the absence of messages from the ESUD, the user devices activate their internal primary spectrum user detectors until ESUD messages are received.