Electromagnetic wave of enemy radar propagated by troposcatter is a valuable candidate for beyond line-of-sight detection. There is no analytical study considering the operating range of passive troposcatter detection system. In this paper, we study the way to predict the operating range, which is dominated by propagation loss. The key propagation loss models including statistic model and real-time model are analyzed. During deducing the latter loss model, Hopfield model is introduced to precisely describe the tropospheric refractivity. Meanwhile, rain attenuation is also taken into consideration. Several examples demonstrate the feasibility of predicting operating range through the proposed method.
