Countries around the world are in the process of migrating from analogue to digital broadcasting techniques for both television and radio. This Report looks at sound broadcasting in the bands below 30 MHz. It briefly examines the underlying reasons for the migration and looks at the technologies involved. Its focus is the DRM system as developed for use in the LF, MF and HF bands. The Report is intended to: 1) Explain why and how a broadcaster might go digital. 2) Be a reference technical document for DRM planning. 3) Provide new information based on the practical experience in DRM. 英：planning parameters;coverage;digital radio mondiale;broadcasting;frequency
ITU-R REPORT BS.2144-2009 history
2009ITU-R REPORT BS.2144-2009 Planning parameters and coverage for Digital Radio Mondiale (DRM) broadcasting at frequencies below 30 MHz