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Antenna for vhf+AIS

Discussion in 'Electronics' started by incoming, Aug 3, 2025 at 8:13 AM.

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  1. incoming, Aug 3, 2025 at 8:13 AM
    #1
    incoming

    incoming Active Member

    Joined:
    Jan 14, 2021
    Messages:
    203
    Location:
    Cocoa Beach, FL
    I have an ic-m506 fixed mount on my 42 post sportfish that is connected to my garmin 8616xsv for displaying AIS targets.

    I would like to add a 2nd vhf and antenna and I’ll probably add a seperate class b or b+ AIS box now or in the future, depending on how everything prices out.

    For radios, I’m considering the garmin 115 or the ICOM m330 but open to suggestions. For the antenna, I have a 14’ galaxy 5230 on one side and a bracket on the other side to mount the second antenna. Would another 5230 be good or is there a better option considering I want it to eventually do double duty for AIS and VHF? I’ve heard mixed things about a VHF and class b AIS using the same antenna with a splitter but I’ve also heard some antennas are optimized for both sets of frequencies. I really don’t have a great spot for a 3rd antenna. I suppose I could mount a dedicated 4’ AIS antenna on my hard top but would that really be better than sharing one of the 14’?
  2. Capt Ralph, Aug 3, 2025 at 9:54 AM
    #2
    Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    13,952
    Location:
    Satsuma, FL
    Use the big stick for long range, use a small stick for short range.
    You don't need to talk to mars when you need to call someone a couple of miles aweigh or less.
    You don't need to hear noise from mars when trying to listen to local reception.
    Put your AIS splitter on the small stick.

    If there is any loss from an AIS splitter, you don't want it on the big stick when you may really need that last fraction of TX wattage.

    The AIS and marine VHF frequencies are so close, Dipole length difference between to two is only an inch or two and AIS transmit power is just a few watts; I used an old VHF stick for years on my AIS.
    Mars does not need your AIS data anyway.