The United States Coast Guard maintains radio stations for communication between Coast Guard units, Coast Guard units and other government entities, and Coast Guard units and the general public. Most communications take place on the VHF marine bands. For long-range communications with aircraft, Coast Guard stations use shortwave single-sideband communications. Weather and safety of navigation forecasts involve facsimile as well as other modes over shortwave and mediumwave transmissions.
According to the NTIA, the Coast Guard is the seventh-biggest user of radio spectrum in the United States. The U.S. Coast Guard maintains a network of VHF radio stations at its shore stations and on cutters and boats, as well as stations of the U.S. Coast Guard Auxiliary. In addition, the Coast Guard maintains a chain of high frequency (HF) and medium frequency (MF) radio stations that provide communications in the Atlantic and Pacific oceans, the Gulf of Mexico, and the Caribbean Sea. Coast Guard VHF Radio stations are currently being upgraded through the Rescue 21 program to meet the US obligations under the Global Maritime Distress Safety System.