In the context of Global Navigation Satellite Systems (GNSS), the measure of the Carrier-to-Noise Density Ratio (C/N0) plays a critical role in evaluating received signal quality, particularly in the presence of Radio-Frequency Interferences such as from a meaconer. This paper presents a dual-step strategy to characterize C/N0 under meaconer influence. First, the theoretical expression of the real C/N0 is computed. Second, a model to predict meaconer-induced distortion on the Moment Method (MM) and the Narrowband-Wideband Power Ratio (NWPR) estimators is derived. The comparison between real and estimated C/N0 reveals a deviation between NWPR, MM and real C/N0. In essence, this work enhances comprehension of meaconing-induced C/N0 distortion.