This paper studies the impacts of transmitters power levels on spectrum reconstruction performances in order to monitor a wideband spectrum. A sub-Nyquist blind sampling scheme based on the Modulated Wideband Converter (MWC) has been considered to achieve this task. Reconstruction performances are evaluated in simulation in terms of correct reconstruction and false alarm rates by studying several multi-level power scenarios. The study shows that the performance of reconstruction depends on the In-Band Signal-to-Noise ratio (IBSNR) of each transmitter. Based on these results, a threshold of In-Band Signal-to-Noise ratio to ensure the correct reconstruction is proposed.