The paper presents a method of analysing the performance of a bandlimited 16-ary quadrature amplitude modulation(QAM) signal transmitted through a bandpass nonlinearity (BPNL), exhibiting AM-AM and AM-PM conversions, and in the presence of additive Gaussian noise (AGN) both preceding and following the BPNL. To illustrate the validity and usefulness of the technique, the symbol probability of a bandlimited 16-ary QAM signal transmitted through a typical nonlinear satellite channel is derived and computed for a four-pole Bitterworth filter as a function of various levels of the on-board travelling-wave tube (TWT) back-off from saturation andBTproducts. Finally, as an example, a study of the effect of increased bandlimiting on the system degradation for this communications system model is undertaken.