AIS Receiver or Transponder?

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jollysailor17

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I am going to invest this year in an AIS system for the boat, linked to the GPS and the VHF DSC. This sounds an excellent idea for crossing shipping lanes at night and in poor visibility especially when I am catnapping and really tired:rolleyes:. I have never actually used one, but on paper it seems a jolly good idea. I am unsure however, whether to buy say a receive only unit, or stump up for a fully fledged Class B Transponder. I want AIS to spot ships in plenty of time and alter course, or make a DSC call and ask them if they have seen me and if so will they be passing ahead or astern? I have a nagging doubt that even if I spend a lot of extra money so I can transmit my MMSI position, whether a big merchantman will pay any attention to a small lowly yacht in its path! Has anyone used AIS, got a Class B transponder or got a clue if its worthwhile?
Thanks
 
For me the most important thing is to be in charge of your own destiny as far as possible, and seeing others around is more important than showing up on other ships' displays. I will be using a NASA AIS display, and the alarm should help me to sleep!

Until AIS for coastal sailing can filter out irrelevant targets, too many transponders end up degrading the excellent information that is there. However, if ever there was a case for the transponder it is for an event like this. Depends on how much you want to spend, and if you don't normally do very much offshore sailing is it still worth the upgrade?
 
Thanks. The Nasa AIS Radar is my unit of choice at the moment and its variable guard alarm is a great asset. I understand that you can plug this into external speakers, so will probably wire it via my iPod dock which is loud enough to wake me from even a deep sleep.
 
Nasa AIS radar

I used the NASA AIS radar on my 09-10 atlantic circuit and found it brilliant. The power drain is minimal and I never had trouble with solar only charging. I used the 16 mile setting usually, and the alarm would sound at 8 mile range. It was very easy to see if courses were converging and make a course change. Usually just zooming in and waiting a bit would show that there was safe separation anyway. The name of the ship usually appears so you can just call them by name, MMSI calling should not be necessary.

Although it would not see most fishing boats or warships, it did allow me to sleep more soundly in deep waters, and it is one piece of kit that I really valued.

The VHF and AIS need separate aerials separated by at least a metre. I have The VHF at the masthead and AIS on the pushpit. For deep waters, I swap them over, as I want to see the ship long before it can see me, but would not need to speak until much closer.

The Class B costs a good deal more, uses more power, and I think if you are advertising your presence you should be awake and monitoring your VHF. Just my opinion of course.

My unit worked well, but the buzzer did fail shortly after our return. NASA will supply a replacement for £3. When I go again (JAC14 ?) I will have a fresh buzzer and carry a spare well wrapped in clingfilm just in case.

Len
 
Don't forget that most fishing boats don't transmit an AIS signal and often don't have as good watchkeepers as ships. The other problem with fishing boats, they don't tend to stick to the same routes as the ships do. So within 100 miles or so you can be fairly certain where you will see ships, fishing boats and other yachts can be anywhere.

I crossed the Pacific last year with a Vesper AIS and I thought it was wonderful. The mistake we made was to only have the internal GPS aerial and sometimes it lost the signal on Port Tack. As we saw next to no ships except near land it was reassuring to be woken up in the middle of the night by the alarm telling me that it had lost the GPS signal. The silly thing was that it was actually a transponder but we couldn't transmit as we didn't have an MMSI number. Something I kept asking for in every port but never managed to get.
 
Of course there are many more things out there than big ships over 300 tons to run into or get into a collision with if one is unlucky or not paying attention. So in clear viz I never sleep longer than 25 minutes, stand in the hatch in my sleeping bag, scan the horizon and then fall back into zombie land. Then have four alarms that make a hell of a racket, as I can fall into a deep sleep, a 120db screamer, a trembler under my pillow, and two other timers that beep hideously. This usually works for me, except the time I got buzzed by a very fast power boat that gave me one heck of a surprise as it shot past at some 40 knots and too close for comfort! When I checked, the horizon was clear, before I had fallen asleep this pocket rocket was on top of me and gave me one hell of a wake up call. You just can't be too careful.
Fog is a different matter and in fog I can quickly become quite paranoid, straining to hear and "see" and generally feeling on edge. It is the same driving or flying in fog, hate the stuff, but as we all know fog and sailing are two things that go together, so just have to get on with it. Having AIS in fog, will I feel be very helpful. Whilst my running albeit slowly into a fishing boat hauling its trawl would be far from fun, being run down by a steel behemoth would really spoil my day. My being able to "see" through the fog and track big ships has to be good. Mind you being run down by a coaster weighing in at 275 tons wouldn't be much fun either, but then I would hope he might have a class B transponder! Something is better than nothing and I still feel AIS is a big step forward.
I recall coming back from Alderney to the Solent, fog most of the way and then becalmed and drifting down towards Portland. No engine in those days. Radar reflector hanging in the shrouds, pushing the plunger of the fog horn for good measure. Out of the fog comes the sound of a ship, it had to be in ballast as its prop could easily be heard splashing the sea at every revolution. Then a barrage of Spanish drifted my way. Still could not see a thing and getting more worried by the second. Then the sound of its wash and I could hear the thump of its engine, the splash of the prop and the guys who were speaking Spanish were now very close indeed. No wind, no where to go. Grab bag in one hand, lifejacket on, but which way to go? Then this shape came out of the fog and lumbered by very close off the starboard quarter, but thankfully making only about 6 knots. Boat hook in hand ready to fend off we bobbed in its wake and as the stern of this vintage looking tramp appeared for a few seconds out of the murk a hail of galley scraps floated down and landed over our decks and in the cockpit! Then she was gone back into the murk. That is the worst one I have had and when the fog eventually lifted and clear viz returned, I said several small prayers of thanks!
I have heard the Vesper is a good unit. When I got my VHF DSC I first had to enter the MMSI before I could use it. The instructions were very clear that if I first used it I would not be able to enter the MMSI and I only had two goes to get it correct before it locked out and then I would have to send it back to Navman to have it recoded. What a faff. I suppose an AIS transponder is a sort of radio as it is a transmitter of the CPA and MMSI. I had not thought of it that way before, so with that in mind it would have to be always on and would not be allowed to transmit without a registered MMSI. I looked at the AIS sets that PBO field tested in the October issue and I see that the Vesper transponder has one of the lowest current draws of 0.25amp, which is the same as the receive only Nasa AIS Radar.
Since I posted, my brother who is a retired master mariner and a keen yachtsman, was telling me that he understands that captains of big ships in the lanes, watch their AIS for yachts, so that at least they know what is out there and if a yacht strays in front of their VLCC they can make a DSC call and request that you change course, as obviously they cannot. However, if a yacht were becalmed and unable to manouvure for some reason and they could see this on their plot in plenty of time, at least they could slow down, rather than just press on and run you down. Which is comforting. Obviously this only applies if you have a transponder and they can see you!
 
AIS

I have a NASA AIS receievr and it works very well - much easier than radar to see who's going where and at what speed. A transponder seems a good idea except that a) big ships probably won't be using it where there are lots of yachts because their screens would be completely cluttered with all of us! b) fishing boats won't be looking out for you because they're too busy fishing and you're too small to cause them any problems. c)A transponder is double the price of a receiver.
Big ships usually show up on AIS and I have found this a pretty reliable way to give warning of their proximity. Fishing boats are normally small enough so they don't have to have transponders, so are invisible on AIS. But I would mention one experience I had: sailing fast one night coming back home over the Sole Bank, spotted a fishing boat on the horizon and as we closed with it, I decided that we would pass safely clear about a quarter of a mile on reciprocal courses. Just before coming abeam of it, the fishing boat switched on a very powerful searchlight and started sweeping it wildly in my direction. It was only at this point that I realised I'd forgotten to switch on the masthead navigation light and I can only assume that my SeaMe radar target enhancer was giving a good enough blip on his radar to set off his alarm and making him think that an unlit ship was bearing down on him. I would guess that most fishing boats keep their radars going and an alarm set to warn them of approaching shipping.
 
The Nasa AIS Radar is starting to look the most appealing, especially price wise. Which SeeMe do you have, Dual S and X band, or X band only? Is it fitted at the masthead?
 
Hi Len
All good points and good to know about the reliability of the Nasa AIS Radar. I am also going for masthead and pushpit aerials, but had not thought of swopping them over. Good idea that. Don't warships, use AIS in peacetime? and if not why not as they are mostly over 300 tons displacement.
 
AIS on warships

Can't quote chapter and verse, but have been told that warships are exempt. Presumably they reserve the right not to advertise their presence. In sea area Plymouth, I had the pleasure of submarine exercises. There were two escort vessels on the surface, one broadcast on AIS, the other didn't.

Some fishing vessels had class B, most not, or not broadcasting. I would think it would be good for them to be seen by big shipping, but they might want to keep their exact fishing locations secret from competitors. Fishing boats gave me most cause for concern; European ones because they were working so far out from land, and Caribbean ones because they have a casual approach to lights and lookouts. I was nearly run down in my dinghy in St Lucia by a fisherman returning at the end of the day, but he did drop off a 3 kg tuna the next day by way of apology.
 
I had a SeaMe, but as the masthead unit filled with water and stopped working I shall replace it with an Echotec, which gives a much better return for the same money. I have no idea how the water got into the masthead transducer as there's only one entry, at the bottom, with an effective gland (it's still full of water after a year ashore!). I can only surmise that water was forced in when I was knocked down, but I wasn't watching it when I went over - I was just hanging on! I'm not convinced that X & S band are necesssary, the extra cost is about double, so I'll just go for the X band version. Other than the water incident, it worked very well.
 
Hello all.
I have got an VHF-AIS with computer on same aerial on the masthead. I also have got an extra aerial on the pushpit.
I am satisfied of AIS. It allows me crossing the Channel with poor visibility more easily.
Obviously remain vigilent by the small boats as un predictable fishing boats.
to see or to see and to be seen, this is a choise.
It is necessary to remain careful.
Jean-Jacques
 
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Hi. Last year I fitted a Standard Horizon DSC VHF which has a built-in AIS receiver. It needs a GPS position input, but is otherwise self-contained, so keeps power consumption down. It proved excellent in the Channel on a murky night - it has a fairly long range (probably because of the shared masthead antenna) so I can use it for planning at what point to cross the shipping, not just reacting to potential collisions.

Howard
 
hrchivers said:
Hi. Last year I fitted a Standard Horizon DSC VHF which has a built-in AIS receiver. It needs a GPS position input, but is otherwise self-contained, so keeps power consumption down. It proved excellent in the Channel on a murky night - it has a fairly long range (probably because of the shared masthead antenna) so I can use it for planning at what point to cross the shipping, not just reacting to potential collisions.

Howard
Click to expand...

Power consumption sounds good. What's the alarm like?
 
The radio alarm does get your attention (and I sleep fairly well) - even if I'm in the cockpit without a remote speaker. It also wakes you up rather effectively if it loses the GPS signal.

A bit more on my setup: I have a Garmin 551 in the cockpit which gives me a very good display which I like to use when I'm actually in shipping lanes. In power saving mode I turn off the 551 and use a handheld type GPS to provide position information to the radio. As well as a target list the radio has a rather small 'radar' type diplay which is not exactly panoramic, but does mean you know roughly where to look without plotting.

Howard
 
Thanks for the tip Howard, only problem recently bought the Navman 7200 DSC VHF, so not really keen to take a big loss only to buy the DSC with built in AIS, though obviously a good idea. I will be using my laptop for decoding weather info linked to the HF SSB receiver and I also have SeaClear plotter software on there with the CD from Visit my Harbour which I bought for £30 and has all 800 UK and Ireland Admiralty Charts. On reading the SeaClear blurb I see I can overlay AIS on the plotter and my position will be shown centre of screen in much the same way as the Vesper and Nasa, but overlaid on a chart, assuming you have loaded the one for your area. VMH sell a USB AIS for £95 which plugs into a VHF aerial. I am always a bit unsure how long my PC will last in the cabin with everything getting saltier and damper by the day, but this might be a worthwhile back up and having the AIS overlaid on the chart could be very helpful for coastal sailing. If interested here is the link for VMH http://www.visitmyharbour.com/downloads-for-seaclear.asp
I recall being becalmed some 20 miles off Castletown I-o-M when a sub periscope broke surface some short distance off our port beam, causing a little bit of excitement. The skipper dashed below, lifted one of the floor boards, turned on the Roberts radio and with Radio One belting out at full volume, dropped it into the bilge. I was rather astonished by this behaviour, but he told me that now the sonar operator would be able to hear the radio and would know we were there!
 
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