Digital calling developments

From Ocean Navigator #99
July/August 1999
The Global Maritime Distress and Safety System (GMDSS), will change the way you use VHF radios beginning this year. The biggest change is the introduction of digital selective calling (DSC) for VHF radios. But before we discuss DSC, let’s look at GMDSS.

The Ross DSC 500 VHF radio was one of the first fully capable VHF DSC units. Most radios now offer limited DSC capability, with full implementation not expected for several years.
   Image Credit: Courtesy Ross Engineering

Very simply, GMDSS is an international agreement that will allow vessels to send and relay automated distress signals. It will also require vessels to have DSC radios to eliminate congestion on the old VHF hailing and distress frequencies. Shore stations, rescue authorities, and other vessels will receive coded position and identification information in the automated signals that will help direct appropriate resources most efficiently. Many oceangoing ships will be required to have satellite communications systems that will be able to forward distress calls.

Parts of the agreement have already been implemented. As of Feb. 1, 1999, approximately 50,000 oceangoing vessels of more than 300 gross tons dropped their listening watch on HF 2,182 kHz. A watch on the old hailing and distress frequency was deemed unnecessary with the automated broadcast feature now required aboard these vessels. The original plan called for the ending of a mandatory watch on VHF channel 16 on the same date, but authorities decided to delay the change until 2005 to allow for the many vessels that do not yet have DSC-capable radios.

The U.S. and Canadian Coast Guards will continue to monitor 2,182 kHz and VHF channel 16 until further notice, and within the U.S. the bridge-to-bridge radiotelephone act will still require most commercial vessels to monitor VHF channel 13 for intership safety communications. GMDSS also requires large vessels to monitor channel 13 when in confined waters. In Canada and the U.S., VHF-based vessel traffic systems will remain non-DSC for the near future, but changes will be coming.

Due to many false alarms, the U.S. Coast Guard has temporarily suspended the construction of its GMDSS receiving system. The Coast Guard is working with manufacturers and international organizations to resolve the problems. An average of seven to eight distress relays are received by the Coast Guard for every actual alert sent. Many of these relays include the identifier of the relaying vessel rather than the identifier of the sending vessel. The Coast Guard must treat every distress relay as an actual emergency, causing delays in responding to the original problem.

Due to problems in implementing the system in the U.S., the FCC has temporarily suspended the requirement for DSC equipment aboard most fishing and small passenger vessels. Vessels carrying six or fewer passengers, including many charter boats, are currently exempt. Canadian officials are experiencing similar problems and are also delaying new DSC radio requirements for small vessels. Equipment

What does all this mean to the pleasure boater? Anyone considering the purchase of a new VHF radio would be well advised make sure the unit they purchase is DSC-capable. Several manufacturers are advertising DSC-capable radios, but these usually require an add-on device that may or may not meet the final regulations. There are various categories of DSC radios suitable for different types of vessels. Most pleasure boats will not need the same capabilities as the average oil tanker. The Coast Guard is still deciding which features will be required aboard various types of smaller commercial vessels and fishing boats. Class D radios will be the ones most likely to be used aboard pleasure craft. This so-called “leisure” set will have minimal GMDSS capabilities and therefore a lower price than units destined for commercial craft. Features missing include dual antennas, so if you are already talking on another channel, you might miss an incoming DSC call on channel 70. Also, Class D sets can’t relay a GMDSS distress call. Class F radios will be handheld units limited in power and features, but still able to make and receive DSC calls on channel 70. Manufacturers will continue to sell non-DSC radios until the Coast Guard, the FCC, and the GMDSS authorities can finalize the regulations. At this time, it appears handheld radios will mostly remain non-DSC, at least until simplified DSC capabilities are approved. By mid-summer 1999, new DSC-radios should become more prevalent. Look for the latest models to appear at the fall boat shows.

If you are applying for a new VHF station license on FCC Form 506, be sure to also request a Maritime Mobile Service Identity (MMSI) number. MMSI numbers for U.S. pleasure craft consist of nine digits that identify the vessel calling. This number will also allow shore stations or other vessels to automatically “ring” your VHF radio, avoiding the necessity of making hailing calls on channel 16. Number please

Whom can you call with a DSC radio? At this writing, not even the Coast Guard within the U.S. can be reached via DSC. The Canadian Coast Guard won’t have full DSC capability until about 2002. However, in offshore waters you’ll probably soon need a DSC radio if you want to contact ships, or authorities in other countries. At this time the best way to contact an oceangoing ship is via VHF channel 16 if you don’t have DSC. Even vessels equipped with DSC-capable radios should still be able to communicate with non-DSC pleasure craft.

There will be a way to ring a DSC-equipped vessel when you don’t know the correct MMSI number. An option will allow safety broadcasts to all ships within range. There will be several options for doing this. The most critical call, the distress alert, will be equivalent to broadcasting a Mayday. A special covered switch will be flipped that will alert all vessels and will broadcast your MMSI and your position, if you have a unit that can interface with your GPS. A distress call will be relayed via satellite or HF radio if it is received by a GMDSS-equipped ship or shore station. Less critical urgency and Securité call options will be available also. A pleasure boat could contact a commercial ship at sea, even without the ship’s MMSI, by using the Securité call to alert vessels in the area, or by using the “all ships call” option.

GMDSS does require commercial vessels to monitor channel 13 when in confined areas. Even without another vessel’s MMSI you should be able to stay abreast of traffic movements and safety situations by monitoring 13. For now, the best procedure for contacting nearby commercial ships is to use VHF channel 13 or 16 even if you suspect they are GMDSS equipped.

For years mariners have been making telephone calls via the services of public coast stations. Soon these stations will be able to take calls from DSC-equipped radios. This should allow mariners to contact the shore stations more readily, and will add a degree of privacy to these calls. A company called MariTEL, which owns the overwhelming majority of U.S. coast stations, has announced it will have DSC-based service available by early next year. However, they will continue to take calls from non-DSC radios. The use of MMSIs will allow coast stations to relay telephone calls directly to your boat, without the need for you to be standing by the radio. The radio will beep to alert you to the incoming call.

By about 2005 the U.S. Coast Guard should be fully DSC equipped and may drop all monitoring of VHF channel 16. Every major radio manufacturer should have DSC equipment for sale, and there will probably be laws prohibiting the sale of new non-DSC radios. These laws will soon be in place in Britain and much of Europe.

Regulations governing small commercial and fishing vessels will be implemented in the next few years. Eventually, pleasure craft that carry radios will probably be required to have GMDSS-approved radios, though non-DSC handhelds may remain the norm.

For now, sailors can be reassured they will be able to contact the Coast Guard and commercial vessels the old-fashioned way. However, as equipment is replaced or upgraded, DSC-capable and GMDSS radios should be considered for maximum utility and safety.

By Ocean Navigator