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When Hurricane Katrina hit the Gulf Coast of the United States in 2005, it severely damaged the telecommunications infrastructure, isolating the area from the outside world. With all the high-end emergency communication gear in its path being knocked out by the hurricane, highfrequency (HF) amateur radio systems played a critical role in rescue and recovery operations. Such tragic incidents have resulted in re-appreciation of the "good old" HF technology that has been an essential part of worldwide information transmission since the advent of radio. HF systems traditionally have been associated with analog voice and very-low-rate data transmission. With the shift from analog to digital in voice communication and increasing demands for high-rate data transmission (e.g., email, Internet, FTP), HF communication has been going through a renaissance. Innovative techniques are required to push the capacity limits of the HF band. Our tutorial provides a contemporary overview of HF communication and discusses cooperative diversity as an enabler to support the challenging expectations of future-generation HF communication systems.