A method to capture random data signals at an end point in a broadband network and process them via digital signal processing (DSP) techniques to determine both linear distortions and nonlinear distortions. In a distribution network, such as a tree and branch cable network, the location of the impairment addition can be identified by determining location of terminals have a distortion and locations of terminals that do not have a distortion. Linear distortions may be determined by an autocorrelation of the captured signal with itself. Nonlinear distortions may be determined by processing measured energy in a vacant band with manufactured energy in the vacant band. If a vacant band is not available, one can be created by demodulating a signal occupying the band, and subtracting the demodulated signal from the measured signal plus interference in a band, leaving only the interference.