Results of remote sensing of liquid precipitation are of considerable interest as they allow obtaining information from large areas and solving practical problems, exploring the physical processes in the atmosphere. However, the widely used single-frequency sensing methods give rise to ambiguous dependence of the differential radar cross section of the drop diameter. Therefore, in the work is analyzed the differential reflectivity at different wavelengths and found ways to ensure uniqueness of solution of the inverse problem to restore the rain intensity using a double-frequency sensing.