Signals acquired from a Combo calibration standard tube used to calibrate for inspection and evaluation of motorized rotating pancake coil probe signals from steam generator tubes. So, Combo tube signals should be consistent and accurate since they have strong influence on evaluation procedure of signals. However, motorized rotating pancake coil probe signals are very easily affected by various factors so that they can distort amplitudes and phase angles which are quantitative terms for signal evaluation. To overcome this problem, we explored possibility of using numerical simulation as a practical calibration tool for the evaluation of real field signals. In this study, we investigated the characteristics of a motorized rotating pancake coil probe and a Combo tube. And then we used commercial software to produce a set of calibration signals and compared to the experiments. Using simulated Combo tube signals, we evaluated deliberated single circumferential indication defects, and these results were compared with experimental signal evaluation results.