January 2002

By D. Scott Croft

DSC VHF: CHANGING THE WAY WE COMMUNICATE ON THE WATER

Last month we started on Digital Selective Calling VHF radio, or DSC. DSC will be coming down the pike within the next few years. Chandleries already have DSC VHF radios in their catalogs and since all new VHF's must now have DSC, these radios are coming whether you like it or not. But to borrow a quote from Martha Stewart, "It's a good thing." DSC chiefly automates and simplifies VHF calling.

As mentioned, DSC was originally intended to improve mayday distress calling and maritime communications. DSC allows for VHF ship-to-ship, or ship-and-shore radio calls to be connected electronically and automatically over the DSC VHF Channel 70. No voice is ever used on this channel, which was set-aside for this purpose. You can even "conference" call to a group of ships in a certain area.

Think of DSC Channel 70 as a place where you go to greet a friend and "handshake," but then go somewhere else to talk. After this electronic "handshake," the call automatically switches to an adjacent working channel where voice communications takes place. You never touch a button after you dial the call. You simply dial the number; it "rings" on the intended vessel and connects. It's just like a telephone at home, but all through your VHF radio.
On the receiving end, you don't have to worry about listening to every hail, because the call is made "point to point," unlike all-ships hailing on Channel 16.

The "Digital" in Digital Selective Calling is a misnomer, as DSC transmissions are in an analog format. The DSC acronym comes from using "digits" to "select" the "call".
The "digit" part comes from a Maritime Mobile Service Identity number or "MMSI" for short. Every DSC VHF-equipped vessel has a unique MMSI assigned to it, which is issued when you register the radio with the FCC. Fortunately, it's a painless process for recreational vessels due to an agreement with the FCC and US Coast Guard that allows Boat US (www.boatus.com), Sea Tow (www.4seatow.com) and MariTEL, The Marine Telephone Company (1-888-MARITEL), who provides ship and shore VHF telephone services, to do this. Commercial vessels still have to get theirs with an FCC Ship's Station License, a $150 fee and considerable headaches.

Think of the "digits" that make up an MMSI as you would a telephone number with a unique address. Every time you make any DSC call, your radio uses this "telephone number" to locate who you want to call. At the same time, the radio also sends out your MMSI number for the "handshake" process to take place, sort of like caller ID. In the case of a DSC mayday call, this is critical.

While the same size and shape of typical VHF radio, DSC VHF radios can be identified by their red distress button on the faceplate, which has a cover to prevent inadvertent operation. This was the pulling of the fire alarm-style mayday feature that I referred to last month.

This one-touch mayday distress button is the key lifesaving feature of DSC VHF. Now in an emergency, you can spend more time putting out the fire, plugging the hole, dropping sail or anchor, and giving aid to the injured - not lip locking the radio. And anyone aboard - even a child -- can press the button for an "idiot-proof" mayday call. Since your DSC radio always sends out its MMSI number on every call, the Coast Guard can identify lifesaving information about your vessel such as length, color, capacity, as well as homeport and emergency contact information.

But the best part of a DSC distress call is that it can remove the word "search" from "search and rescue". It does this by connecting to your GPS, which transmits your location to all DSC equipped vessels and shore stations within range of your vessel. Rescuers see an exact latitude/longitude appear on their DSC radio display. I wouldn't consider a DSC VHF without this connection capability (called an NMEA interface), which also allows you to link and integrate with other vessel electronics, such as a chartplotter.

So now the Coast Guard can potentially know who you are, what you look like, and where you are - all without ever saying a word.

So what's the bad news?
Today, the Coast Guard does not have DSC receive capabilities in their shore-based National Distress System (radio towers). Channel 16 voice mayday calling is still the only recognized "911" system for boaters.
Current Coast Guard planning forecasts DSC VHF implementation in 2006 - 07, but that doesn't mean no one will hear you now. In our case on the Hudson, every ocean going freighter, or what's termed a "compulsory carry" vessel (usually a commercial vessel) already has DSC VHF aboard. And of course, anyone else who installs a DSC VHF will hear you, too.
When MariTEL, in the midst of building a nationwide DSC VHF ship-and-shore-telephone system, puts a radio tower near New York City sometime by 2003, they'll hear you as well - at least on the lower river, New York harbor, and its approaches. And while not widely acknowledging it, I am aware that some Coast Guard vessels and USCG Group Moriches on Long Island, does have DSC VHF. But rightfully so, they don't want you to rely on DSC just yet.
It's ironic that the US is the one of the last developed countries that hasn't fully implemented DSC. But with Sept. 11, I predict the government will step up its timeline because DSC can improve the Coast Guard's command and control capabilities. For example, DSC allows the Coast Guard to potentially reduce the amount of hoax distress calls. DSC can track a vessel's course. It can aid in law enforcement. It can bolster aural watchstanding, which can be prone to human error. Urgent safety messages can be "conference called" to a group of vessels in a geographic area, and there's much more.
I'm a firm believer that Digital Selective Calling VHF will change the way we communicate on the water forever. If I was one of the 300,000 persons who buy a VHF this year, I'd certainly consider it.

Telephone 914-332-7688 email dscroft@erols.com