U.S. Coast Guard Radio Stations - Modes of Transmission

Modes of Transmission

These stations broadcast navigation and marine safety messages through several means, including Navigational Telex transmissions on 518 kHz; facsimile transmissions of National Weather Service charts; single sideband transmissions; and Simplex Teletype Over Radio SITOR narrow-band direct-printing broadcasts. In the 1960s through the 1980s, these transmissions were broadcast live, with the interval signal of "Semper Paratus"; however, now, using Voice Broadcast Automation (VOBRA), a computerized voice ("Perfect Paul") reads the voice messages.

NAVTEX transmissions are identified by the last letter of the callsign of the station. Each station transmits a NAVTEX broadcast six times a day, including two rebroadcasts of the general forecast. A NAVTEX broadcast includes maritime navigation warnings, weather forecasts, ice warnings, Gulf Stream locations, radio navigation information, rescue messages, and marine advisorys. Each station has 2 NAVTEX transmitters.

Besides broadcast messages, Coast Guard stations handle direct traffic between aircraft, cutters, boats, and shore stations on VHF, MF, and HF frequencies, including the HF Data Link encrypted e-mail system and Digital Selective Calling (DSC), which uses radio telephone to send digitally-encrypted signals to either one receiver or a group or receivers.