Ever since early mariners floated a chip of lodestone in a dish of water to form a crude magnetic compass, mariners have been using electronics to help conduct a safe and successful voyage. The March Meeting presentation on DSC, Digital Selective Calling, touched the tip of an iceberg regarding the on-going revolution in marine electronics. Following the presentation, several questions hinted at an incomplete understanding of the new capabilities offered by modern marine electronics. This article attempts to parse some of the issues and clarify relationships between DSC, AIS and the other TLA, Three Letter Acronyms, bandied about in the world of modern marine electronics.

Why marine electronics? Well, fundamental situational awareness is essential for a safe and successful voyage. At minimum, you need to know where you are (if you don’t know that, you’re in real trouble), how fast you’re going (to predict if and when you’ll arrive at your destination), the depth of water under your keel (to assure your trip will not be unexpectedly foreshortened), and the presence of other vessels with which you may collide (and ruin your whole day). Modern marine electronics provides all that and much more.

But let me say this about that. As anyone with a modern cell phone knows too well, increased functionality comes at the price of increased complexity. It’s inescapable. The user manual of my original marine VHF radio ran to 9 pages; my current one consumes 128 pages. And, yes, to learn to use some of the functions that my current radio provides I actually had to RTFM: Read The (ahem) Fine Manual. Well, parts of it anyway. It keeps putting me to sleep. But it’s on my cell phone for those times when I’m particularly ambitious.

So if you’re still using a flip-phone in 2016, and digital to you simply refers to the fingers you count on, stop reading right now--this article isn’t for you.

VHF/DSC

Marine VHF radios have been used for voice communication among vessels and shore-stations for decades. Radios have become much more affordable over the years. In 1978, a few years after SSSS was founded, a basic marine VHF radio cost $669,the equivalent of $2,435 in 2016 dollars! Recreational vessels are not typically required to have a VHF radio. But today you can get a marine VHF radio for a couple hundred dollars, and there is really no excuse for not having one, and knowing how to use it.

For convenience, the allocated VHF spectrum is divided into channels. Channel 16 is designated as the International Distress, Safety, and Calling channel. It is a law that all boaters with VHF radios (voluntarily equipped or not) monitor channel16 while underway, though I doubt anyone has been thrown in the brig for violating it; stupidity has a way of creating its own punishments.

Anyone who has monitored CH16 for long has undoubtedly heard some clown gleefully rambling on about his mother-in-law’s colonoscopy until a clearly irritated Coast Guard officer breaks in and shuts him up with a terse, “…Channel 16 is a Distress and Calling channel ONLY. Please take your traffic to a working channel.” Working channels (e.g. 68, 69, and 72) are assigned to be used by boaters for routine intership conversations.

Still other VHF channels are designated for specific purposes, e.g. 22 for the USCG, 14 for Southern Puget Sound VTS, 13 for Bridge Tenders. Monitoring some of these channels as well as 16 (using the scanning feature found on most VHF radios) often provides very relevant and actionable information for mariners, particularly in the more congested portions of the Salish Sea. See http://www.navcen.uscg.gov/?pageName=mtvhf for the official list and http://goo.gl/A23McI for an abbreviated version.

Now, traditional VHF functionality relies solely on voice communication. While effective, there are several limitations. First of all, in congested areas, there is often a lot of chatter on 16 with multiple boats trying to make contact with multiple other boats--it can be tough to break in and hail your buddy. To address this congestion, Channel 9 is designated an alternate hailing frequency, another good use for channel scanning.

In a real emergency, you can clear channel 16 by hailing “Mayday”. The first thing the CG will want to know is the nature of your emergency, then your position (lat/lon), number of persons on board, PFDs, and so forth. It takes a while to find and communicate all this information clearly and accurately, and meanwhile you may have better things to do; your boat may be filling up with water, for instance, with no one to work the pump. Or it might be useful to locate and get your spouse back on board.

DSC. Digital Selective Calling, is a technology built on existing marine radio to send text messages between stations. The pre-formatted digital messages are information-rich and sent much quicker than voice messages, generally within 3 seconds. Each character is transmitted twice, and the range for receiving intelligible text messages can be 25%greater than for voice messages. Current radios (DSC class D for recreational use) constantly monitor for DSC messages with an independent, dedicated internal receiver.

DSC is implemented in-both VHF (short range) and HF (long range) marine radios. Some years ago, VHF channel 70 was removed from use as a voice channel and devoted to digital messages. When DSC is used, your radio transmits a short text message on channel 70 which is received by all DSC equipped radios in range. If the message is addressed to you. the “selective” in DSC) your radio responds with a “ring”. If it’s not addressed to you, you continue in blissful ignorance and silence.

Clearly, you need to have an “address” in order to receive selective messages. That’s where MMSI comes in. The MMSI, Marine Mobile Service Identity, is like a telephone number that identifies your boat. You get one, program it into your radio, and… Voila! Radio messages directed to your boat cause your radio to “ring”.

When you receive a DSC message and your radio rings, you have the option/obligation to “Acknowledge” the call. This may be done automatically, or you may elect to press a button to “answer the phone”. Included in the DSC call text message is the channel number on which the caller wishes you to reply. When you acknowledge a DSC call, manually or automatically, your radio and the caller’s radio both switch to the channel number specified. You then key your microphone and begin your voice conversation. No hails, no negotiating a working channel, (almost) instantaneous connection. Slick, huh?

In an emergency, hit the red button on your VHF, and your MMSI number is transmitted to the Coast Guard. Immediately, the Coast Guard knows the size, color and type of vessel, ownership and so forth, data that you provide when you request an MMSI number assignment. The Coast Guard can also get in touch with an emergency contact person you may designate.

The red button on your VHF automatically transmits a DSC Mayday message not only to the Coast Guard but also to All Ships within range of your radio. Not sinking? There are optional All Ships messages that act as the DSC equivalent of Pan Pan or Securité Securité situations.

So far so good. But in order to know your position when a distress call is initiated, a GPS must be connected to the VHF DSC radio. Recently, some handheld and fixed mount VHF radios are manufactured with a GPS built in. Earlier radios, however, require wires from an external GPS to be connected. It’s not difficult, but it is a task that must be done to realize the full capability of DSC radios for emergency signaling and other position-related functions.

So now we have a radio that knows who and where you are. What else can be done with this ability? Well, say you’re buddy-boating with another vessel and you’ve arrived at the rendezvous point. You’ve lost track of your buddy and want to know how close he is in order to have the beer chilled and steaks on the BBQ when he arrives. DSC radios have a Position Request function that fits the bill.

Simply enter your buddy’s MMSI, or select it from your radio’s directory, send a Position Request DSC call, and his radio will receive the request and automatically reply with his LAT/LON. No intervention is needed on his part. Of course, if he’s sitting on his secret fishing hole, he can always turn off the automatic response to position request calls, and you will get no response.

Suppose your buddy has broken down, and he needs your help. He can report his position to you by initiating a similar Position Report function. When you receive the DSC message, your radio will ring. You can save his LAT/LON as a waypoint, and your radio will calculate and display his range and bearing to help you navigate to his aid.

Selective messages can also be sent to a Group of boats. Each boat must enter the pre-determined Group MMSI into their radios. Typically, you store it in your radio’s directory/”phone book”. Thereafter, any call to the Group MMSI will cause all radios in the group to ring. Acknowledge the call and you will be switched to a channel where there is a great party-line conversation going on.

Our SSSS Cruise Committee has set up a group identity that can be used to get in touch with all cruisers; see Marvin for details. Or the Race Committee might set one up to get in touch with all racers, say when the course is shortened, or an accident has been reported and assistance may be needed.

There are a couple of other DSC functions, as well. Calls are logged, so if someone calls you with an unrecognized MMSI, you can get back to them later if you wish, without having to write down their MMSI. You can also automatically track the positions of up to four other vessels simultaneously.

All of these features come at a cost, of course, adding complexity to VHF operations. More problematic, however, is the fact that there must be a minimum critical mass of vessels in your peer group using DSC in order to provide the opportunity to practice using DSC and master its use. If none of your buddies has a telephone, it hardly pays you to get one and figure out how to use it.

Eventually, you’ll have to RTFM. But once you do, come out on an SSSS cruise and practice, say the upcoming Memorial Day Cruise for instance. Ultimately, however, the safety benefit of being able to use a single red panic-button to send an effective Mayday to the Coast Guard would seem to be reason enough to make DSC work for you.

But wait—there’s more!

MFD

A couple of years ago, NOAA stopped publishing nautical charts on paper. So 20^th century. Oh, you can still get paper charts as Print-on-Demand (if you’re still living in the Pliocene), but most of us now have transitioned to electronic charts (RNC or ENC) displayed on an LED screen integral to a Chartplotter. Actually, the term chartplotter is only a bit less dated than paper charts (it is firmly in the Pleistocene). No, the current device for such purposes is the Multi-function Display, or MFD.

The modern MFD not only plots all the charts ya got, but it also overlays a radar on the chart, replaces land areas with satellite images from Google Earth, shows isobars and wind speed and directions in your vicinity using GRIB files, renders bottom contours around you in 3-D, and also displays all of your instrument data: wind speed true or apparent, depth, speed (water, ground or VMG to windward), distance and ETA to waypoint ... not to mention engine RPM, oil pressure, temp, etc. when you’re motoring. It can display video camera feeds, connect to the Internet, and tell you when to tack to reach the mark most efficiently. And once you’re sufficiently situationally aware, you can forget all about the chart and use the MFD to launch your stereo system to play Ride of the Valkyries at top volume over the cockpit speakers just as you’re passing the committee boat at the finish line.

Obviously, to do all of this the MFD must be well-connected. And one of the useful connections is to your VHF/DSC radio. Then, when an incoming DSC message arrives, data from the calling vessel is forwarded to your MFD; since the DSC message provides the vessels identity, MMSI, and position, the calling vessel can appear as a little icon on the screen so you can immediately see who they are and where they’re calling from. Kind of like Caller-ID with a geographical overlay.

With some MFD/VHF combinations, you can even initiate a VHF DSC call to another vessel by simply poking its icon on the screen with your finger. Then they can hear Ride of the Valkyries, too.

MFDs are not necessarily cheap, although a B&G Vulcan 5, with built-in GPS, is available for just over $400. And you may have to upgrade your speedo, wind, and other sensors to feed it with the relevant ship data to get maximum functionality. But you can repurpose an old laptop to run OpenCPN, an excellent open-source, read free, chartplotting program. NOAA provides free electronic charts of all US waters to work with it. So it’s possible to cobble together a very workable MFD for not much more time, or money, than it takes to read this article. Learning to use the tool effectively, however, will take longer. Again, RTFM.

AIS

Basicaly AIS, Automatic Identification System, lets you see, and be seen by, other vessels in your neighborhood that are similarly equipped, day or night, sun or fog, even around islands or headlands that would otherwise prevent visual contact. An AIS transmitter periodically transmits your vessel’s identification, position, and course and speed (COG/SOG) to everyone in your vicinity. An AIS receiver detects transmissions from other vessels, and with the data received all of the vessels and their movements can be automatically plotted on a suitable display (see MFD).

AIS supplements, and in many ways improves on, marine radar which the primary method of collision avoidance. AIS is required for use aboard all passenger vessels and other vessels larger than 300 gross tons and is increasingly used for recreational and small commercial vessels, as well.

AIS shares much technology with VHF DSC radios: AIS transceivers, transmitter/receiver aka transponder, utilize special VHF channels (87B, 88B) for rapidly transmitting digital data, have built-in DSC radios and a GPS receiver. AIS also relies on MMSI for vessel identities. However, an AIS unit does not provide the capability to contact another vessel directly for a voice dialog, a separate VHF/DSC radio is still required for that.

AIS transceivers come in two flavors: class A for large commercial vessels, and class B for the rest of us. Class A transceivers transmit more data, more frequently, as befits the higher STW of supertankers, and operate at a higher power with higher priority. A Class A transceiver has an integrated display, integrates with a variety of other ship systems, and is comparatively costly. A Class B transceiver transmits at a lower power, less frequently, is largely self-contained; although it requires a display to be useful, it need not be integrated, a separate MFD will do, and is available for less than $500.

If your philosophy is basically hide and watch, it is possible to simply buy an AIS receiver so you can see vessels that transmit AIS messages without actually transmitting one of your own. Indeed, some VHF/DSC radios contain a built-in AIS receiver and a rudimentary display that shows range and bearing to transmitting vessels. For the best viewing, however, the AIS receiver should be connected to an MFD which overlays all vessel positions, headings and tracks on an electronic chart of the area.

There is considerable comfort, however, in installing an AIS transceiver and knowing that your data is being transmitted. Then that supertanker knows precisely who he is running down, and all the world can watch and gasp as it happens (see marinetraffic.com, below).

AIS features include a list of all AIS vessels in range, the calculation of the Closest Point of Approach (CPA) for each vessel based on a projection of your, and the other vessels course and speed, and Time to CPA which lets you know how quickly you’ll be run over if you don’t do anything about it. With some integrated MFD and VHF radio systems, you can simply poke a finger on a vessel icon shown on your display and initiate a DSC call to the bridge of the target vessel. Once connected, you can pass the time of day with the skipper of the vessel that’s about to run you over.

To see, for free, the kind of information you might get on your own boat, check out http://www.marinetraffic.com/ . This site reports worldwide vessel traffic using a network of shore-based stations that monitor AIS channels and report local sightings to a central server. Very cool.

BFD?

Your call. But I wouldn’t leave home (waters) without it.

John Sherman, Grendel