A handheld leakage detector for finding digital QAM signal leaks in a HFC network, comprises a radio receiver, a leakage receiver, leakage sampler, a correlator, and a display. The radio receiver receives samples of the QAM signal taken from the HFC network, called “reference samples.” The leakage receiver receives a QAM leakage signal, which is related to the QAM signal from the HFC network. The leakage sampler samples the leakage signal to form leakage samples. The correlator performs a coherent cross-correlation of the reference samples and the leakage samples, to produce a correlation peak. A value is determined from the correlation peak and displayed on the display. The value generally becomes more optimized as the detector approaches the leak. The leak is sought by iteratively changing the position of the detector until the displayed value becomes substantially optimized or the leak is found.