Connectivity and security of tactical mobile ad hoc networks (MANETs) can be enhanced significantly by explicit consideration of radio propagation as this not only allows determination of route feasibility and minimization of radio frequency power, but also avoids detectability of emanations. Tactical MANETs (and increasingly general MANETs) typically have geolocation and terrain information available, however as they are likely to be deployed in urban, broken, or indoor environments, simple Free Space or Two-Ray Ground models are not adequate. Although highly accurate radio propagation models exist, they require considerable computational resources and are hence unsuitable for incorporation into real-time protocols, particularly on resource-constrained platforms such as MANET nodes. We therefore propose a simplified, scalable ray-optical radio frequency propagation model that incorporates a Two-Ray Ground model and takes reflections and deflections on terrain features into account. Although our proposed model does not incorporate a comprehensive model of all physical effects, we argue that the approximation provided by our model is sufficient and suitable for the purposes of enhancing network performance and accuracy in the frequency range currently used by wireless networks. The model was incorporated in the NS-2 simulator and validated both using simulation and experimentally.