Marine Electronics Journal - July/August 2010

RTCM Report
VH F:
Your radio can do more

By Bob Markle, President New technology is leading to VHF radios with advanced features. RTCM—the Radio Technical Commission for Maritime Services—is developing standards that will help bring innovative capabilities to your new radio. RTCM is an international, non-profit, scientific, professional and educational organization involved in the creation of technical standards for marine communication and electronic navigation.

It has been about 15 years since the international Global Maritime Distress and Safety System (GMDSS) was introduced for commercial ships on international voyages. Although ships and boats that were not required to meet the Interna- tional Convention on the Safety of Life at Sea (SOLAS) were not directly affected, most countries introduced modernized radios for all maritime commu-
nications. The most obvious change to VHF radios was the introduction of Digital Selective
Calling (DSC) and the addition of the red distress button. In the US, you may see the des-

ignation “SC101” somewhere in the documentation of your VHF radio. The reference is to RTCM Special Committee 101 on Digital Selective Calling, which developed a standard for a simplified DSC system that would interoperate with the international GMDSS system, but would be less expensive than a full-featured DSC radio. This standard was adopted in the regulations of the Federal Communications Commission (FCC) as the minimum standard for radios for use on boats that were not specifically required to carry radios (“voluntary” stations in FCC-speak).

Originally, the GMDSS system was reserved for distress and safety communications. This restriction, and the fact that DSC radios were in the minority for many years, led to a lack of use and lack of familiarity with DSC. Now that is changing. A few years ago, the FCC lifted the restriction on use of DSC only for distress and safety purposes, and now it can be used for routine communications, and mariners are discovering the advantages of having VHF radios with Maritime Mobile Service Identity (MMSI) “telephone numbers.” The Coast Guard is also rolling out Rescue 21—a system of coast stations that enhances the distress and safety functions, including the red “distress” button.

DSC can now be used for routine communications rather than just distress and safety situations. Here, Coast Guard Petty Officer 2nd Class Derek Crews talks to a boater over the VHF aboard a 33 foot special purpose craft.