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  1. #21
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    Crikey, this is an old thread!

  2. #22
    jecuk's Avatar
    jecuk is offline Registered User
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    I have just fitted a class B unit both for receive and possible assistance that I can get from the broadcast side. I accept it may not be perfect but who knows - it might help a merchant ship see me even if late in the day.

  3. #23
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    Quote Originally Posted by jecuk View Post
    I have just fitted a class B unit both for receive and possible assistance that I can get from the broadcast side. I accept it may not be perfect but who knows - it might help a merchant ship see me even if late in the day.
    It is a fair point that AIS is not always used as an alert on big vessel's bridges, but what it is used for is identifying other vessels.

    If they do spot a yacht and want more info, then they know just where to get it. Which has to be a good thing.

    Three years on and we have still not fitted it to any of our boats, as I said back then there are other things above it on the list.

  4. #24
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    lenseman is offline Registered User
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    Quote Originally Posted by Malthouse View Post
    . . . . . Three years on and we have still not fitted it to any of our boats, as I said back then there are other things above it on the list.
    What you are basically saying is that you are broke, just like me!
    regards David - DSW Marine Engineering
    www.dswmarineengineering.com

  5. #25
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    [QUOTE=tome; Have to take issue with your understanding of Class B transponders. They will be limited to 2W power output, but even so this should provide a useful range up to 20M. As for power drain, the duty cycle of the transmitter will be no greater than 1:67,500 or equivalent to 2.5 micro amps so no significant drain even on the smallest yacht]


    I agree power drain is not a major issue but the average transceiver uses about 0.5 Amps in transmit mode and 0.2 Amps in receive only mode.

    More to the point a friend of mine is a Thames pilot so he sees the bridges of more big ships than most and he confirms that only a minority of ships have their AIS receiver linked to their Radar/Nav screens. For most it is a minimum keyboard device at the back of the bridge which they consult only when they want the MMSI of a target they have aquired on radar.

    If you can afford both an AIS transceiver and a radar transponder fine. However, if its a question of one or the other why spend money on a transceiver you know will only be seen by a minority of ships when you could spend less on a radar transponder that will will be seen by the majority?

  6. #26
    Malabar is offline Registered User
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    Quote Originally Posted by tome View Post
    Agree for the time being. But then, where would you put it on a sliding scale versus a See-Me?
    I found the following advice from a professional to be pretty well balanced:
    http://www.yosc.org.uk/html/announce...navigationaids

  7. #27
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    Quote Originally Posted by Talbot View Post
    who was talking about narrow waters - not me - and yes I would hazard a guess that 14 years of watchkeeping at sea all round the world would probably give me some knowledge.
    Yes Mark but those who have been twice around the IoW know much more than you do and object to you disagreeing with them!
    Since I crossed the channel with you a couple of years back I am confident in your judgement at sea and in this case (not always, that's asking too much!) I agree with you entirely. My philosophy on a boat is much the same as in a car. Defensive. I am sure some merchant ships are well manned but bloody sure some aren't too! AIS B is the latest whizz bang. It relies on many assumptions that are not particularly well founded and I too prefer to know where others are and what they are doing well in advance to take appropriate action rather than broadcasting "this is me and I have right of way" In fact I have always thought that was an ideal tombstone inscription. I have fitted an AIS receiver and interfaced with the chartplotter it's a great aid. To tell others where I am, I am considering fitting a Seame whotsit which I would think far more useful than AIS B at this time....

  8. #28
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    Lets do a side by side comparison then....

    AIS B:

    Cost - c420 including backup VHF antenna.

    Alerts you of other vessels' locations of certain navigation marks. Does not necessarily alert other vessels of your presence, but does convey information should they choose to look you up.

    Also tells (smaller) port authorities and rescue services who you are.

    X RTE:

    Cost c360.

    Alerts you of other vessel's presence, but not location. Alerts other vessels of your presence and location, but does not impart much information other than perhaps that you are a small craft.


    In summary then, there is little to choose in terms of cost. One works well if you want to broadcast your presence and the other works well if you want to broadcast more detailed information as well as receiving similar back.

    For me this is a difficult trade off, the waters are quite crowded with commercial stuff but fog is also a regular challenge. Since the greatest hazard with either is being run down by something large that did not see you... and the best way to avoid that is to be aware of them and get out of their way then I think AIS B has the edge.

    I for one am not content to sit in my boat sending out a big strong PING safe in the assumption that "they" will go around me. Likewise being in fog and knowing that there is something big out there somewhere is not 100% reassuring.

  9. #29
    timbartlett Guest

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    Quote Originally Posted by boatmike View Post
    My philosophy on a boat is much the same as in a car.
    So you don't bother switching your lights on because so long as you can see other vehicles, there is no need for them to see you?
    Quote Originally Posted by boatmike View Post
    I am sure some merchant ships are well manned but bloody sure some aren't too! AIS B is the latest whizz bang.
    One of the most fundamental of the colregs is the one that requires all vessels to keep a proper lookout by all available means. For a ship's watchkeeper to arbitrarily choose to ignore his AIS just because it's "one o' they 'lectronickery things" is unprofessional -- criminal, even. I don't disagree that some do -- but AIS has been around for a good few years now: bridge displays are getting better, and watchkeepers are gradually getting used to it. A growing proportion of watchkeepers will never have been to sea without it: for them, it is as much a part of standard bridge equipment as radar.
    Quote Originally Posted by boatmike View Post
    It relies on many assumptions that are not particularly well founded
    At least it doesn't rely on smoke and mirrors like radar reflectors! AIS B does work. Radar reflectors do not. Even the MAIB, after the Ouzo collision, failed to find a single commercially-available radar reflector that met the basic minimum performance standards.
    Quote Originally Posted by boatmike View Post
    rather than broadcasting "this is me and I have right of way" In fact I have always thought that was an ideal tombstone inscription.
    There is no such thing as "right of way" at sea. Telling people "I am here" is not the same thing at all.

  10. #30
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    Quote Originally Posted by timbartlett View Post
    There is no such thing as "right of way" at sea. Telling people "I am here" is not the same thing at all.
    Isn't that what Mike said?

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