Abstract
<jats:p>The paper addresses the practical challenges of implementing and optimizing a coherent radio direction finding (RDF) system based on the KerberosSDR platform. The study focuses on the modernization of the software stack to ensure full compatibility with modern computational environments and stable real-time signal processing. A significant part of the research is dedicated to achieving and maintaining strict phase coherence across four independent RTL-SDR channels, which is a fundamental prerequisite for high-resolution Direction of Arrival (DOA) estimation. The author performed a comprehensive refactoring of the system’s core modules, specifically addressing critical compatibility issues with contemporary NumPy and PyQt5 libraries, transitioning to updated complex number standards and modern graphical layout widgets. By adjusting the sampling rate to a fixed value of 1.024 MHz and optimizing the USB data stream, the study successfully eliminated sample drops and phase drifts that previously hindered the accuracy and reliability of the MUSIC (Multiple Signal Classification) algorithm. The experimental setup involved a 4-element uniform circular array (UCA) with an optimized element spacing of 0.333λ. This specific configuration was strategically chosen as a compromise to balance angular resolution and suppress spatial aliasing, ensuring stable performance especially in complex multipath environments typical for urban radio monitoring. Furthermore, the paper details a rigorous calibration protocol utilizing an internal noise source to synchronize the tuners at the hardware level. The results demonstrate that the implemented hardware-software complex provides stable and accurate azimuth estimation in the FM broadcast band. The research highlights the critical importance of proper noise-source calibration and precise physical antenna alignment–referencing the true North–for the reliability of the spatial pseudospectrum visualization. The findings offer a comprehensive practical roadmap for utilizing low-cost SDR hardware in professional-grade radio monitoring, signal intelligence, and electronic warfare training tasks, proving that software-level optimizations can significantly enhance the capabilities of budget-friendly hardware.</jats:p>