Boats & Gear
- Category: Boats & Gear
- Created: Thursday, 07 June 2012 22:43
- Written by Charles Doane
NO DOUBT YOU'RE ALL WONDERING what happened with those SAIL Magazine MOB tests I mentioned a couple of posts ago. You can skip to the end of this post if all you want is to find out what's happening with the comic's masthead (no, we didn't actually lose any staff members during the tests). But I urge you to read the whole post if you want to learn something about the new SafeLink R10 personal AIS rescue beacon that was only recently approved by the FCC.
This is a game-changing piece of equipment in that it should make it possible for crew on a boat to easily and reliably locate other crew who have gone overboard. The R10 beacon, which is very compact and light and can easily be clipped to a lifevest or jacket, transmits a Class A AIS signal over an advertised range of about 4 miles. Any MOB victim wearing the thing need only turn it on, and at once they become a live AIS target on all active AIS receivers in the vicinity.
Our test team (myself, senior editor Adam Cort, associate editor Meredith Laitos, and intern Hilary Sharp) originally planned to strap the R10 to an MOB dummy and cast it adrift, but the Coast Guard in Portland, Maine, where we conducted our tests aboard Lunacy last week, put the kibosh on that scheme. They wanted to be absolutely certain we recovered the beacon, so asked instead that we test it from a fixed location.
This seemed reasonable, so we tethered Oscar, our homemade dummy, to a mooring in Diamond Cove on the north end of Great Diamond Island and lit off his R10 unit. My Vesper AIS Watchmate receiver aboard Lunacy immediately announced it had received a message that read "MOB Active" and also referenced what purported to be an MMSI number, together with the date and time of the beacon's activation.
Once I acknowledged the message, it was archived on the Vesper's message list, and the display from then on referenced the target's MMSI number, its range, bearing, status, etc., with no blatantly obvious indication that the target was in distress.
We motored away from Oscar, changed course several times, and even put the better part of Great Diamond Island, which is reasonably high (over 100 feet), between us and Diamond Cove. Checking against a separate GPS chartplotter, we found that the Vesper constantly displayed a perfectly accurate bearing and range right back to poor old Oscar.
Lunacy is not fast enough for us to have efficiently tested the range of the beacon, but when we checked back with the Coast Guard we learned they too had seen the target on their AIS display almost exactly four miles away. What was disturbing, however, was that they also told us they saw nothing that suggested to them that the R10's transmission was in fact a distress signal.
I discussed this later with James Turner of Oriola Ltd. (formerly McMurdo Ltd., which owns the Kannad brand and manufacturers the R10), and he shared the following information:
1) What my Vesper unit told me was a unique MMSI number was in fact a "nearly unique" transmit ID number assigned to Oriola SART beacons. The 97 prefix (see the photo above for the complete 9-digit number) indicates the transmission is a distress call. More specifically, the 972 prefix indicates a transmission from an MOB.
What makes the number "nearly" unique, James explained, is that Oriola has been assigned 10,000 of these numbers, so every 10,000th unit produced will share a number with a predecessor. (Thus, there is a statistically infinitesimal chance that two beacons with the same number might be ignited in the same area at the same time.)
2) The "status" of the R10's transmission--number 14 (again, see the photo above)--also always indicates that it relates to an emergency message.
Once you know these things, of course, it should be easy to identify an AIS MOB alert on any receiver, but it seems likely that most boaters (including, apparently, the U.S. Coast Guard) actually don't know these things.
It is up to AIS receiver manufacturers to produce equipment that makes more of a fuss over MOB alerts, and so far, according to James, only Garmin (and to a lesser extent Raymarine) have stepped up to the plate. No doubt more manufacturers will eventually follow suit. Meanwhile, I can strongly recommend the SafeLink R10 and similar units as a reliable way to locate an MOB in the water, as long as you go to the trouble to learn how an AIS MOB signal will be interpreted by the AIS receiver on your boat. (Note: you can also purchase dedicated AIS MOB alarms, like the Digital Yacht AIS LifeSaver, to make sure there is no confusion.)
Also, you obviously cannot assume anyone else in the area will correctly interpret an AIS MOB signal, so it is probably a good idea to broadcast your beacon's transmit ID number when making an MOB Mayday transmission.
In communicating with James, he asked that I send along a photo of Oscar, and after studying it he also provided an important critique of our testing procedure. The range of Oscar's R10 beacon, he noted, was likely degraded by the fact that it was well clear of the water and was not more horizontal. The beacon is in fact designed to operate while in the water, or in close proximity to it (the water helps ground it), and should be more or less horizontal (as it would be when worn by an MOB victim floating on his or her back) so that the antenna, which deploys at a right angle to the unit, is more or less vertical when deployed.
According to James, independent tests in the U.K. have suggested the R10 may in fact have a maximum working range of 6 or 7 miles when deployed in this manner.
He also sent along this photo showing how Oriola deploys the beacon in its tests:
If you want all the gory details on how the MOB retrieval portion of our tests went, I urge you to check out the August issue of SAIL.
We had a lot of fun doing them, and I'm sure you will find them of interest.
MASTHEAD CHANGES: Per my own request, I will be demoted from executive editor of SAIL back to editor-at-large, starting mid-July, so I can pay more attention to my ailing dad. Meanwhile, Adam and Meredith will be promoted to executive and senior editor respectively. The comic is now also looking to hire an entry-level associate editor, so if you want to live the life of a glamorous underpaid sailing journalist, this may be your big chance. Check here for details.