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Marine VHF - broadcast FM antenna isolators?

Discussion in 'Boat Electronics' started by Mika, Feb 20, 2008.

  1. Mika

    Mika Guest

    Currently have a car FM with its own antenna just above deck. Wish to
    use my mast-mounted marine VHF antenna for receiving broadcast FM as
    well. There are many devices available what sort of split the
    antenna cable to VHF and FM. Do these in practice provide enough
    separation so that I would not "fry" my FM receiver should I transmit
    on marine VHF while broadcast FM radio is swhitched on? 25 watts to
    receiver could do some damage...

    Mika






    --

    A bad day on the water is better than a great day on land.

    Lähetätkö e-mailia? Vaihda osoitteen eka (vai oliko se toka?)
    kahdeksikko numeroksi viisi.
     
  2. I don't know about a car FM, but I have two Marine VHF-FM radios that use
    one antenna.
    I have an
    a.. SHAKESPEARE ELECTRON
    a.. Automatic Two-Way Antenna Selector
    a.. Only $84.99 USD
    When a radio mic is keyed, the other radio is isolated from the antenna.
    Doesn't matter which radio is used, the other is automatically protected.
    I've had it for several years and both radios work fine.
    When a mic is not keyed, both radios receive. That's convenient for me as I
    can scan several channels on one radio and remain on another channel on the
    other radio.
     
  3. Larry

    Larry Guest

    They work but do cause some sensitivity decline in your marine VHF because
    of the poor way they are designed, more like a cheap radio than a piece of
    RF hardware, which would cost them money to make. They're lossy, both on
    incoming and transmitting.

    Your VHF antenna is NOT made or tuned for any FM radio band. It's not
    going to be a great FM antenna to receive FM stations miles and miles away.
    Any consumer FM radio is a terrible piece of equipment, even expensive
    ones. They're made to sell, not to perform, and all have poor receivers,
    which is why FM broadcasters are running 100,000 watts of power so they can
    hear them.

    If I were you, I'd leave my VHF piece of safety equipment attached to its
    antenna, not make it part of the entertainment system that's not going to
    save you from the sinking, if you get my drift.
     
  4. Larry

    Larry Guest

    An inherently terrible idea for safety at sea.

    The weakest, most exposed link in your VHF system has no backup.

    So, there you are sinking off Drum Island with ONE dead antenna and two
    perfectly good VHF radios unable to call for help from that ship 8 miles
    away you can see the top of.

    TWO radios should have TWO antenna fed by TWO SEPARATE FEEDLINES and TWO
    POWER SOURCES, if possible, and it is. REDUNDANCY is why spacecraft
    operate way beyond their expected life.

    Please put up even a little Metz Manta 6 on a handrail mount. Do it for
    the children, please?
     
  5. GregS

    GregS Guest

    I would agree to have separate FM antenna.
    I did share the FM antenna with a CB. That was kinda a mess. The CB
    is disconnected now.

    greg
     
  6. Larry

    Larry Guest

    (GregS) wrote in @usenet01.srv.cis.pitt.edu:
    The CB was a mess since 1857....(c;)
     
  7. Mika

    Mika Guest

    You are probably right. Most consumer electronics pieces are not
    quality, but overprized junk. Better keep separate antennas. Besides,
    have already installed another power bus to feed VHF, nav lights, echo
    and log in case main battery fails. Only 6Ah battery standby, but who
    need nav lights during summer here in 60 degrees north ;)

    Mika



    --

    A bad day on the water is better than a great day on land.

    Lähetätkö e-mailia? Vaihda osoitteen eka (vai oliko se toka?)
    kahdeksikko numeroksi viisi.
     
  8. Larry

    Larry Guest

    Except, curiously, things made in Finland. My Nokia N800 Linux internet
    tablet is a fine piece of Finnish equipment, very nicely made. My next
    Sellphone will be a Nokia, too, because of it.

    Too bad Nokia isn't interested in marine electronics.....
     
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