A new era for VHF

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Jim Benedetto, fishing his 33-foot Bertram TunaNut out of Sandwich, Mass., is living the Digital Selective Calling (DSC) dream. “DSC is the best thing to come along in a long time,” said Benedetto. “I use it every day. When you’re hooked up to a 500- to 900-lb bluefin, you don’t have time to give your friends the lat/longs, and if you don’t call them in the first five minutes it’s too late. Just one push of a button and they have it.” Benedetto and his fishing buddies have equipped themselves with high-end Ross DSC VHFs, permitting not just instant position sharing, but private scrambled communications. Benedetto claims half a dozen hookups last season were a direct benefit of DSC communication to or from the TunaNut.


One can imagine that Benedetto fishes with more peace of mind knowing that if he suddenly gets into trouble, he can use the same one-button-push technology to send out an all-stations automated distress signal. At least he has friends that might hear it. Benedetto, we found, is the enthusiastic exception to the rule; most early adopters of DSC VHF radios in U.S. waters are discouraged. Typical is one participant in a web news group for voyagers who signed off: “DSC equipped, but I don’t know what for.”

There was a lot of eager talk about this new technology in the late 90s, but it has not quite materialized. The U.S. Coast Guard is still not monitoring DSC Maydays, ship-to-shore operations have not yet updated to DSC features, and most hardware setups remain fairly expensive and complicated. It’s disheartening to adopt a new communication protocol and find no one’s listening.

It seems safe to predict, however, that the promise of this new technology will soon outweigh the problems, and many mariners will start equipping themselves with full-bore DSC capability, TunaNut style. The Promise

Digital Selective Calling started life nearly 20 years ago as part of the Global Maritime Distress & Safety System (GMDSS), an amalgam of hardware and software standards arduously worked out by agencies like the International Telecommunications Union (ITU) and International Maritime Organization (IMO) to improve maritime distress and safety communications. Enhancements in routine communications were seen as a nice byproduct of the project.

The DSC part of the system refers to the ability of various communication devices to collect, transmit, and receive standardized fields of pertinent information. DSC radios interface with GPS receivers so they can transmit time and position (as well as speed and course) data. They contain memory registers that can be programmed to hold at least a vessel’s Maritime Mobile Service Identity (MMSI), and possibly more data like other stations’ MMSIs, vessel’s destination, short text messages, etc.

The “digital” part of DSC is somewhat of a misnomer as current DSC radios actually talk in coded analog information. A DSC VHF modem turns data into an analog stream, transmitting at 1,200 kilobytes per second. This is pretty slow, comparable to the very first computer phone modems, but it does the job. A DSC VHF built to the barebones SC-101 specification can transmit on command a distress call with position, time, and MMSI. Any station within range monitoring DSC Channel 70 will get beeped. More advanced radios will display all the data, perhaps even a text message describing the type of distress. Search and rescue teams can reference an MMSI database that should describe the vessel and owner and may include other useful information. All the DSC radios will automatically switch to channel 16 for further voice communication about the emergency.

The “selective” part of DSC refers to the ability of these radios to direct a call to any one or several MMSIs. TunaNut’s captain has listed his friends’ numbers in his radio just like a home speed-dialer. He selects one or several of them to call; DSC initiates the calls on 70 and switches all requested stations to a working voice channel. Some radios can maintain a list of DSC calls that came in while the unit was unattended, something like a caller I.D. system. That’s just the beginning of the cool communications tricks that can be built on top of the basic DSC functionality.

At any rate, through the 1990s, GMDSS systems were put in place and most commercial – often called SOLAS (Safety of Life at Sea Convention) – vessels were required to install and monitor DSC communications in steps and according to the areas they transit. Deep-sea ships usually voyage into Area A3, which means they must carry and monitor one of the DSC-style Inmarsat satellite systems or DSC HF, as well as the DSC MF radios of near-coastal Area A2 and the DSC VHF of Area A1, which runs around the coasts to 20 miles out.

As of Feb. 1, 1999, GMDSS implementation was fully in place when all SOLAS vessels were required to stand by DSC VHF channel 70. Shortly thereafter in the U.S., the Federal Communications Commission (FCC) required that any new-model VHF for any type of boat have at least minimal DSC capability. It would seem reasonable to presume that, as these sorts of regulations went into effect, the major maritime nations that promulgated them would install the official systems to receive DSC distress calls. Many did, but the U.S. has yet to open its Area A2 officially, or even begin to build Area A1.Problems and Solutions

Some DSC owners are downright angry with the Coast Guard for failing to have a modern communications system in place, but most observers see the slowness as just symptomatic of an under-funded agency with too many missions it is earnestly pursuing.

Part of the problem is that the entire Coast Guard communication network is due for a rebuild. A Coast Guard unit called the National Distress and Response System Modernization Project (NDRSMP) last summer awarded phase 1 contracts to Lockheed Martin, Motorola, and Science Applications Internation Corp. to set up demonstration and validation systems at Valdez, Alaska; Woods Hole, Mass.; Seattle, Wash.; New Orleans, La.; and Miami, Fla., this coming year. Then, in phase 2, one contractor will be chosen to build out the whole network. Unfortunately, full and official Area A1 coverage is not expected until about 2005, which is none too soon as that is the year that SOLAS vessels will be excused from monitoring channel 16 and only required to stand quiet watch on 70. (By the way, the notion of quiet watch – a radio that only makes noise when someone is in distress or is calling you specifically – is no doubt another carrot for voluntary users of DSC. The fact that commercial shipping would eventually stop monitoring the voice safety channel is the stick.)

Possibly the most important news to report about DSC is that MariTEL, which is communications subcontractor to both Lockheed and Motorola in the drawn-out NDRSMP project, has already begun to build an advanced DSC network. The company claims that it will be listening on channel 70 over a significant part of the coast by the end of this year and the entire coast next year. MariTEL is in discussions about just how it will deliver DSC distress messages to the Coast Guard, but it has no doubt that those calls will be delivered. In other words, a de facto Area A1 – with probably the same towers and radios that will be used in the official one – is being built right now. That and the powerful ship-to-shore capabilities of MariTEL’s new system may be the keys to wide adoption of DSC, but other problems are being solved.

The Coast Guard has not been the only agency frustrating early DSC users on our shores. Recreational boaters who were excused in the mid-1990s from having to obtain a VHF ship’s license found out that the only way to get an MMSI was to purchase such a license, at a cost of more than $100. In 1997 the FCC stated: “As licenses are no longer required for vessels less than 65 feet long operating on VHF exclusively in U.S. waters, the FCC is working with industry to develop a streamlined, economical means of obtaining MMSI in the future.”

The future turned out to be the fall of 2000, when Boat/US and MariTEL signed Memorandums of Understanding (MOUs) with the Coast Guard and the FCC permitting them to issue MMSI to so-called voluntary vessels. It may have taken a while, but the good news is that both organizations are doing it for free. Boat/US has an easy on-line sign-up system in place right now at www.boatus.com. (The amount of personal information requested for MMSI registration has apparently led some doubters to fear that Boat/US is going to invade their privacy, but, in fact, this is specifically prohibited in the MOU.)

Another problem that has colored the early years of DSC has been a fairly high incidence of uncancelled false Maydays, primarily on the MF and HF bands that the Coast Guard is unofficially monitoring at some locations and also by relay from SOLAS vessels. Apparently these radios are unfamiliar enough that even professional mariners are capable of accidentally keying the DSC distress button, and then failing to declare a false alarm on the appropriate voice channel.

Joe Hersey Jr. of the Coast Guard’s central communication unit said, “If the person who inadvertently sent a distress call replies over the radio stating that the call was inadvertent, that false alert is not a big problem for us. However, if the person sending a false alert does not respond, we are forced to assume something catastrophic happened that prevents a response, and that is a big problem for us.”

The Coast Guard has issued a Special Notice to Mariners about the problem, and reports that incidents have decreased. DSC VHFs coming to market these days put the distress button under a protective lid to avoid accidents, and are improved in other ways. Some early models had to be returned to the manufacturer just to program in the MMSI; now the user or installer can input the MMSI themselves at least once (to avoid hacking).

Early recreational-level DSC radios often had no features beyond basic distress calling. Now there’s a feature competition underway with MMSI dialing by boat name – called “while you were out” lists – GPS data repeating, DSC Class D dual receivers (for constant watch on 70), and more. All are available at moderate prices.

Jim Tindall, MariTEL’s vice president of sales and marketing, has 30 years in the industry, including a stint as head of marine products at ICOM. He’s proud that nine VHF manufacturers will be introducing MariTEL ready radios this spring. Let’s have a look at what MariTEL is up to.Maritel’s MariNET

Many boaters know MariTEL as the company that bought up most of the coastal VHF marine operators in the mid-1990s. There was some griping about the loss of local flavor as MariTEL centralized and partially automated the service, and there were doubts that even a more efficient system could survive with so many boaters using cell phones for ship-to-shore communications. Now we know that MariTEL had a much bigger vision of what VHF telephony could be.

In 1998 MariTEL won an FCC auction for the many still-unlicensed public correspondence channels and started assembling a team of companies to build the entirely new MariNET, using DSC as the key gateway technology. It’s the giant second step in MariTEL’s plan to take VHF ship-to-shore from the level of switchboards and party lines to the functionality of digital cellular, only with greater range and reliability.

MariTEL has contracted with American Tower Corporation to be the anchor client occupying the top 100 feet of 286 new towers along the U.S. coast and inland navigable waters. Topping these minimum 300-foot towers will be radio direction finder (RDF) antennas with the design capability of zeroing in on a handheld VHF transmitting on low power from six feet off the water at 20 miles. Regular, fixed VHF units will get overlapping coverage 50 to 100 miles offshore when MariNET is fully deployed.

The wireless part of the communications loop will be handled by entirely digital Cubic radios, which are both frequency and bandwidth agile. Harris Corp. is designing the base station equipment and software, all interconnected with a redundant ATM (Asynchronous Transfer Mode) fiber optic network provided by Williams Communications and multiple ties into MariTEL call centers and MCI nodes to the regular public phone network.

For starters this means that anyone with a MariTEL-ready DSC VHF can dial any number ashore without having to pick a channel (MariTEL now has nine in most places) or deal with an operator. Shore parties can direct-dial a boat with only the MariTEL I.D. number (to protect the privacy of MMSIs) without knowing the boat’s location. All SOLAS class A through C DSC VHF radios already have the software code for automated ship-to-shore telephony built in; as mentioned above, we’ll soon see a lot of models geared to non-SOLAS users. These radios will come with a free one-year subscription to MariTEL, including 30 minutes talk time and an MMSI, “kind of like AOL” says Tindall.

Four of these new radios will also be able to transmit/receive short text messages. This won’t be true e-mail – DSC modems don’t have the horsepower – but more like pager messages. MariTEL is building this system with coastal and inland commercial customers as its main target, and thinks fleet operators will use the messaging along with DSC’s position-polling ability to keep track of where their boats are and what they’re doing. We won’t be surprised to see some third party set up a short message to e-mail system for small boats using MariTEL’s pipeline.

In fact, MariNET’s capabilities invite all sorts of advances in VHF. For instance, there are proposals afoot to create more VHF channels by narrowing the bands from 25kHz to 12.5kHz or less. We could have double to quintuple the channels eventually, and MariNET will be ready for any and all changes (that’s the frequency agile part), even the ability to consult its MMSI database and set itself up for the particular channels your radio has. Features like this will be invisible to the user, just like the system’s ability to hot-swap frequencies and even pass calls from one tower to another. What the user should notice is rock-solid communication and plenty of free channels even if – as MariTEL hopes – the network gets busy.

MariNET will also support radios that can transmit dial tones to operate answering machines or PBXs. MariTEL already uses a busy tone to cloak the ship-to-shore side of conversations in their present system; MariNET will be capable of completely scrambled calls, as radio manufacturers adopt it, using the sort of public key encryption scheme widely used on the Internet. By the way, the present non-DSC marine telephone services will be completely supported by the new system. In fact, the rates for the new system will remain the same, with subscriptions at $50 to $200 per year with effective call prices of $1-$1.75 minute. Eventually MariTEL may add a charge for operator assistance (i.e., a non-DSC call).

MariNET will also be ready for the exciting advent of purely digital VHF radios, which Jim Tindall thinks we’ll see within two years. This technology will support full duplex voice traffic and data speeds up to 56kps, similar to the best phone modems today. Then coastal vessels can have regular and reliable e-mail, web, fax, and telephone all through one device. Further out is the possibility of integrating digital VHF sets into the high-bandwidth, but DSC VHF-based, Universal Automatic Identity System (UAIS) now being adopted by large vessels. Imagine having a display showing who every vessel in your vicinity is and what they’re doing. “We most definitely do believe there will be a recreational market for VHF AIS,” said the Coast Guard’s Joe Hersey Jr.

More to the present, MariTEL plans to have MariNET fully operational along the entire Gulf Coast and lower Mississippi by July 2001. Towers for many East and West Coast commercial ports will go on-line by the end of this year, and the whole system will be filled in during 2002. With MariNET’s attractive DSC ship-to-shore system and unofficial ear for DSC distress calls, with MMSIs now for free, and with manufacturers competing to make DSC features available to voluntary vessels, it seems quite likely that boaters will start installing and using this technology. As cart follows horse, might we start adding MMSIs to our business cards and address books?

There are skeptics. We came across a gentleman who might be described as an informed telecom curmudgeon (retiring as a senior engineer with several patents in the field). To him “DSC is an idea whose time has come and gone before it got here.” He believes MariTEL will have a hard time competing against improved cell service, combo cell/satellite Globalstar, and the revived – and possibly much cheaper – Iridium, especially as the FCC requirement for position reports from cell phones goes into effect later this year.

“The 911-enhanced system will be there whether the CG is ready for it or not. I would think it likely that by 2005 or so the number of boats with 911-enhanced cell phones will exceed those with DSC radios by an order of magnitude. Do we really expect that the SAR folk will restrict themselves to communications not present in much of the user base?”

We’re skeptical of his skepticism about DSC, but we do see a future when the poor Coast Guard watchstanders may have all sorts of devices and channels to monitor, and we users all sorts of telecom choices. Contributing editor Ben Ellison lives in Camden, Maine, and writes regularly on marine electronics topics.

By Ocean Navigator