Sky wave interfering signals evaluation for digital local broadcasting services in the 11 meter band

A characterization of the potential long distance sky wave interferences between DRM local services in the 26 MHz band is presented in this paper. To do this, a statistical analysis of the ionospheric conditions that cause such electromagnetical impairments has been done in order to contribute to the ITU-R Question 127/6 concerning the use of digital modulation in the 26 MHz band for local coverage. The study is based on two parameters typically used when studying the sky wave propagation: the Maximum Usable Frequency and the field strength received level. Monthly median values of both parameters were predicted by means of two simulation tools referenced by the ITU: REC533 and VOACAP. Also, the corresponding upper deciles were calculated to obtain results more appropriate for planning digital services. Simulations were carried out for every month of the year and hour of the day considering two different transmission antennas and a wide range of SSN values that account for the sunspot number variation in a whole solar cycle.