Synthetic Aperture Radar (SAR) creates the effect of a very long antenna by analysis of signal properties. Simulators play an important role in the initial phases of developing SAR Processing Modules (SPM). They make improving theories, testing new or developing concepts easier, faster and less expensive. This article describes an instance of real time working SAR simulator, which is in operation. The basics of how it works, types of data transfers, and comparative analyses of working modes are shown.