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Radio communications possessing high signal quality and long-distance propagation have traditionally been difficult to achieve reliably over shortwave bands (up to 30 MHz). This is due to the analog modulation schemes in use and the vulnerability of shortwave radio to atmospheric disturbances. The development of the Digital Radio Mondiale (DRM) standard in 2001 provided digital coding methods, audio compression, and data protection features for shortwave transmissions. With DRM, nonprofit humanitarian broadcasters in underdeveloped nations have a reliable high-quality, long-distance transmission technology of lower cost than satellite radio services. The development of versatile DRM receivers is therefore necessary. This paper presents the design of a DRM receiver capable of demodulating a single DRM transmission, or “channel,” and compares the receiver's performance to that of the commercial DRB-30 receiver. Plans for future improvement of the receiver's overall signal-to-noise ratio and resilience to signal fading are discussed, including the addition of multi-channel reception capability and the Maximum Ratio Combining (MRC) diversity algorithm. |
