Can I put all of this on the same radar mast...?

Discussion in 'Marine Electrical / Electronics' started by offshore27ns, Dec 6, 2017.

  1. offshore27ns

    offshore27ns Senior Member

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    4' Open array
    ais antenna
    gps antenna
    vhf antenna
    xm/sirrius

    Just wondering if there is a requirement for any minimum separation?

    My goal is to get it all on the same mast so I dont have to have more than one hole passing throught the roof
     
  2. Wharf Rat

    Wharf Rat Captain

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    You're going to want to get at MINIMUM 4' horizontal separation of the AIS and VHF antenna's, as far away from each other as you can get. The GPS and SiriusXM antenna's can basically be mounted on the same mast, we'll usually put those on opposite sides of the mast wings inboard, with the antennas mounted outboard. See below for the NMEA's guidelines for horizontal and vertical spacing. Copyright NMEA®.


    [​IMG]
     
  3. F/V First Team

    F/V First Team Captain

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    *quietly prints that out for the wall*
     
  4. captjohn

    captjohn Captain

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    Footnote "b" is pretty important!!
     
  5. BlueMack

    BlueMack Senior Member

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    The copyright police will be on you before the epoxy sets up!!!!
     
  6. F/V First Team

    F/V First Team Captain

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    No worries there
    Epoxy was thrown out years ago
     
  7. backman

    backman Captain

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    Hey Chris - to follow up on our conversation the other day:

    How far should the VHF antenna be from the mast itself? Turns out my antenn is mounted directly in line with the mast with perhaps a bare 3-4' separation.
     
  8. backman

    backman Captain

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    Pulling this back from the dead, I am adding a AIS transponder this winter which means I need to add another GPS receiver and another small HF antenna to my mast.

    The mast is 5’ wide wingtip to wingtip , has a GPS receiver on either end, a VHF antenna in the middle of one wing. If I read this table correctly I want to redo my mounts so I have VHF on either wingtip, 5’ apart and I can locate GPS antennas wherever I wish on the mast as long as they are 6” apart.

    Is this correct?
     
  9. cb34

    cb34 Captain

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    It n, post: 248588, member: 7493"]Pulling this back from the dead, I am adding a AIS transponder this winter which means I need to add another GPS receiver and another small HF antenna to my mast.

    The mast is 5’ wide wingtip to wingtip , has a GPS receiver on either end, a VHF antenna in the middle of one wing. If I read this table correctly I want to redo my mounts so I have VHF on either wingtip, 5’ apart and I can locate GPS antennas wherever I wish on the mast as long as they are 6” apart.

    Is this correct?[/QUOTE]
    All manuals say to mount the gps as low to center of gravity on the boat with a clear view to minimize pitch and roll...
     
    cb34,
  10. backman

    backman Captain

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    Got to squeeze another GPS antenna on the mast, thinking rather than adding another VHF antenna to use a splitter off my #2 antenna versus trying to jam another one onto an existing tight configuration.
     

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  11. Wharf Rat

    Wharf Rat Captain

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    Larry,

    Just saw this now, but you'd much be better off going with any one of the newer SOTDMA Class B AIS transceivers,which transmit at 5W vs the pre-existing CSTDMA Class B AIS units (basically everything from 2008 to 2018) which TX at only 2W. Going forward I'll try to just refer to them as 'SO' for SODTMA, and 'CS' for CSTDMA..
    Sorry.
    Furthermore, the SO units transmit at a much faster update rate vs CS, and are not limited to available slots (too long to explain!). Essentially, SOTDMA is the same transmission delivery method as the commercial and IMO mandated Class A AIS. So a huge advantage, and they don't really cost more. Been a big deal since the FCC finally approved a bunch of models earlier this year, not to mention a lot of those models have built in 'Zero-Loss' amplified splitters for the VHF; so not required to add ANOTHER VHF antenna for the AIS. All depends on the application.

    In addition, the GPS antenna mounting location for performance is not as crucial when it comes to most AIS rigs, it as it's not designed for navigation level accuracy. and the GPS receiver is actually in the AIS module itself; the GPS antennas are simple 5V coaxial style 'extension' aerials; not WAAS or differentially augmented sensors, and are used for providing the AIS with the vessel's position, Speed over Ground/Course over Ground; the antenna position itself is important for the programming of the unit as it provides the dimensions of the vessel AND the relative location of the antenna on the fore/aft and port/stbd axis of the boat. Obviously this is much more critical on Class A applications; a 300 meter tanker might have the antenna mounted all the way aft and 100 meters to stbd on an antenna mast; the AIS needs to know where the actual antenna is in order to make sure someone doesn't think they have clearance in limited visibility.

    I'll explain more over the phone tomorrow, but wanted to share it with anyone else who is considering an AIS. Below is a link to a great Panbo article (Keep in mind this was published 3 Years Ago, so it was prior to FCC approval on most of the units available) but still does a MUCH better job explaining the differences between the original Class B AIS which used CDMA, Class A (SODTMA) and the wonderful SODTMA Class B units..

    SOTDMA Class B AIS, the "new" middle way? - Panbo

    [​IMG]
     
    Last edited: Nov 28, 2018
    Larry7777 likes this.
  12. backman

    backman Captain

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    Wow, one if th rare times I say TMI, but that article was dense!

    I already have the FA50 and antennas, steal of a deal from someone else’s upgrade. For my purposes the use is very simple, it replaces manual ARPA on my radar. I’m comfortable with the slowness and inaccuracy of ARPA so even an outmoded class B is an upgrade. More important to me is that the AIS information will be on the screen for someone else at the helm who doesn’t know how to use ARPA.

    I’ve been woken up one too many times either drifting the canyons or transitting the lanes by someone driving or watching who didn’t understand what they were seeing either on radar or with their interpretation of lights. Even a simple slowly updating vector is better than nothing in that situation.
     

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