Study of the ionospheric interference for planning DRM local services using the 26 MHz band

This paper presents a statistical characterization of the sky-wave interference conditions for DRM (Digital Radio Mondiale) local services in the 26 MHz band. This work is the first step to analyze the feasibility of a world frequency planning for local services in this band and is focused on regular ionospheric propagation. The analysis has been based on two parameters: Maximum Usable Frequency (MUF) and field strength received level. Values of these parameters were obtained by means of two prediction tools, both of them referenced by the ITU and developed by the NTIA/ITS: REC533 and VOACAP. Simulations were carried out defining combinations of a wide range of Sun Spot Number (SSN) values characterizing a complete solar cycle, 12 months per year and 24 hours per day. This first study has focused on Europe and was done for 20790 circuits after establishing 5 representative transmitters and taking this continent as the reception area. From the resultant database, cumulative distribution functions, as well as other significant statistics, were computed and analyzed for both parameters. The obtained results show the ionospheric conditions that give raise to interfering signals between DRM local services and establish when their propagation is critical.