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Thread: AIS Class B Transponder Questions

  1. #1
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    Default AIS Class B Transponder Questions

    This is a good time of year to be ruminating over boat improvements. My own experience, as well as anecdotal info from others, suggests that shipping traffic does not always maintain a radar watch. But do container and cargo ships have AIS receivers? What do people think about class B transponders for coastal and offshore sailing...as a tool to reduce risk of bumping into a ship? I am also interested in the cost part of the equation....both in terms of money and power. My boat is set up for sailing with low power load: Monitor steering offshore, LED tricolor, NASA AIS receiver, no chart plotter, no radar, etc. The little NASA "Radar" unit is one of the best purchases I have made and draws only about 50 mA; 100 mA with the backlight turned on. How much power does a class B transponder require? I think Culebra and perhaps a few others have a transponder installed...any thoughts?
    Richard
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  2. #2
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    http://www.em-trak.com/PRODUCTS/Class-B/Class-B.aspx shows typical specs....I have one but haven't installed yet. Customer service superb- they wrote and delivered a custom configuration file for me in <48 hrs.

  3. #3
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    I have heard of the Em-trak combined with the Vesper WatchMate display for a way to use a transponder and receiver without the need to run a computer or chartplotter. But like other manufacturer specs that I have looked at, the specs for the Em-trak seem to provide two values for power consumption....one for receive only, the other for transmit. But my understanding of transponder function is that the transmit mode is intermittent. The B100 model, for example, shows a peak power use of 2amps. If that represents transmit power (peak power use) it is of little value in preparing an energy budget...unless it transmits continuously, which I don't think it does.

    Anyone know what a good 24-hour power consumption estimate is for a class B transponder? I have emailed ICOM but don't have a response yet.
    Richard
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  4. #4
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    Em-trak can provide this info. I believe they make the electronics used by a number of other companies, and are very responsive as I noted. John

  5. #5
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    I had the em-trak unit on Idefix. Average power consumption is pretty low, around 300 mA, I think. I paid less than what I'd paid for a receive-only unit two years previous. It's tiny and weighs nothing. There's wiring for a stealth switch if you don't want to be seen, or it's consuming too much power.

    Ships over 100 tons are required to have AIS Class A transceivers. Lots of smaller boats now have receivers. I think Class B transceivers are the way to go. For me it was a no-brainer for crossing the Pacific.

    Adrian

  6. #6
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    Thanks Adrian! I have sent emails to both Em-trak and Icom asking for good overall energy budget numbers for their AIS transceivers (rather than the specs which show standby and transmit numbers but not an overall 24-hr power consumption number) and have received no responses. Your figure of 300 mA (translated to 8 amp hr per day) looks pretty good to me. What did you use for display with your em-trak? I assume your 300mA did not include display...is that right?
    Richard
    Libations Too

  7. #7
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    pogen is offline Sailing canoe "Kūʻaupaʻa"
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    Does anyone know of a ClassB transponder that has an integrated active splitter? I have receive-only AIS at present, but am thinking hard about upgrading to transmit/receive, and want to keep using my current antenna.

    Too bad Standard Horizon doesn't make a VHF with AIS transceive capability all in one box!

  8. #8
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    I would guess they will soon as they seem to really hit a home run with their 8100/8150.

  9. #9
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    Richard,

    Take my number with a grain of salt, it may have been as high as half an amp. I would get you an exact power consumption figure for the AIS, but unfortunately I've taken the unit off the boat (I'm selling the boat but like the AIS enough to want to keep it), but I think .3A is definitely in the ballpark. I remember being quite pleased with how little it drew, even while transmitting. I used my netbook running OpenCPN for a display. All in all, with AIS, netbook and instruments I was running at about 1.5 to 2A.

    I would be careful about using a splitter with an AIS transceiver. I would think having the antenna disconnected while it's sending a signal might be detrimental to the unit, and since they send every 30s it might be hard to prevent.

    Adrian

  10. #10
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    As a newbie to the water can you recommend these devices ? You seem to but I see various choices to buy. Can you tell me what would best suit a low power cruising yacht 50 ft ?

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