AIS question

  • July 07, 2014 7:08 PM
    Message # 3040252

    Now that I have AIS I'm wondering what sailors might use for an appropriate CPA & TCPA alarm setting. My AIS defaults to a CPA alarm of 1 nm and a TCPA of 1 minute.

    That might be fine for a powerboat but it sounds awfully close for a sailboat.  Anyone have any suggestions/recommendations for these AIS alarms?

  • July 08, 2014 4:18 AM
    Reply # 3040511 on 3040252

    I use 3 miles when out at sea and far from shipping lanes.  I reduce it when there's lots of traffic and false alarms.  I turn if off when approaching port.  Ships and tugs that I've talked to seem to be comfortable with 1/2 mile CPA; not me.

    My Standard Horizon VHF/AIS does not filter alarms well.   As seas rock my boat and rock the other vessel, the projected track, and thus CPA swings wildly and it may cross the alarm zone for a fraction of a second.  That triggers a CPA alarm, then the alarm disappears before my finger can reach the button to silence the alarm.  I've had this happen when the other vessel is as much as 35 miles away.

    Then it alarms again with the next swell seconds later.  Drives my crazy.  I scramble to turn the alarm off, but new alarms coming while I'm navigating the menus cancel my actions.  Sometimes it takes 10 or more attempts to successfully turn the alarm off.

    They really need a filter on the alarms.  If the CPA is inside the alarm zone for 60 seconds, trigger the alarm.  If it leaves the alarm zone for 60 seconds, then cancel the alarm.

  • July 10, 2014 7:32 AM
    Reply # 3042949 on 3040252

    I can see how that would happen. And I can see how it could get annoying. How do other AIS receivers deal with it?

    Do you have the new GX2200 with AIS/GPS?

  • July 10, 2014 10:40 AM
    Reply # 3043074 on 3040252
    Deleted user

    We have an Icom AIS and have never had this problem.  It could be that the ICOM is a stand alone unit and doesn't rely on interfacing with other devices.



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