Patent ID: 8605775

Claim:
A method for measuring Hum in a digital television (DTV) signal comprising quadrature amplitude modulation (QAM) signals using a testing device for testing QAM signals on a cable television (CATV) network, the method comprising: a) receiving the DTV signal with the testing device, the testing device comprising a DTV receiver and a controller coupled thereto, the DTV receiver comprising a first QAM demodulator for demodulating a first QAM signal comprised in the DTV signal, wherein the DTV receiver further includes a plurality of automatic gain control (AGC) stages in a signal path of the first QAM signal, each AGC stage comprising an AGC register for storing a current AGC gain value of the respective AGC stage, b) sampling values stored in one of the AGC registers at a pre-defined sampling rate R that exceeds two times a Hum frequency to obtain a first sequence of AGC samples; and, c) using the controller to store and analyze the first sequence of AGC samples, or at least a portion thereof, for evaluating Hum in the first QAM signal.