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Lost my VHF screw

Discussion in 'Boat Electronics' started by Howard, Mar 23, 2006.

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  1. Howard

    Howard Guest


    I have a VHF whip that mounts to my radar pedestal. The radar is on one
    side and the other is a flat plate for mounting. I was having some
    trouble with the VHF (poor reception) so I took the antenna off to check
    the connection. When reinstalling the mounting screw/bolt jumped

    My question: Does anyone have a clue what size scew/bolt I need?

    Yes, silly question with little info, but maybe............

    The boat, with the antenna, is on the hard very far away (1,000 miles)
    and not readily available for inspection.

    The antenna mount is such:
    The base of the antenna has a threaded hole.
    There is a matching hole in the aluminim mounting plate.
    The coax has the outter shield stripped back and the center conductor is
    terminated in a ring connector.
    The coax connection is covered with heat shrink.

    I bought the boat with this arrangement so I have no first hand
    experience with it.

    It is a whip fiberglass antenna, maybe 8' long.

    The antenna has no external markings indicating make.

    Sent with cautious optomisim,

  2. Lynn Coffelt

    Lynn Coffelt Guest

    This may be useless information, but many US made antenna mounting
    fixtures and whip attach bolts are 3/8" by 24 threads per inch.
    What sounds alarming to me is that the type of connection I think you
    are describing, and the length of the whip, make it sound an awful lot like
    you are messing with a "marine" CB antenna. If that's the case, the VHF
    radio would tend to be less than red hot.

    Old Chief Lynn
  3. I have a feeling this is a wetsuit job!

  4. Lynn Coffelt

    Lynn Coffelt Guest

    That sounds like a good guess, too. My guess was based a little on the
    coax termination method........... from OP:
    "The coax has the outter shield stripped back and the center conductor is
    terminated in a ring connector"
    Haven't seen many marine VHF antennas that used anything except some
    sort of UHF or N connector arrangement.
    Old Chief Lynn
  5. Larry

    Larry Guest

    FEDEX coulda had a new part now.
  6. Jack Erbes

    Jack Erbes Guest

    That thread is the 3/4" NPTS, the nominal O.D. is just under 1" so it
    has become called 1"-14 TPI in the marine industry. NPTS means National
    Pipe Thread Straight, it is the same as common 3/4" pipe and fittings
    but not tapered.

    Standard 1" bolts are either 8 TPI (NC) or 12 TPI (NF) and a strong and
    yard mechanic can get 1" NF bolts to work on the antenna stubs. For a
    few threads anyway. :>)


  7. When making custom mounts for the Marine 1"X14 Mount Threads, I use
    my pipe threader with an adjustable die set, and cut the threads
    just slightly deeper than the normal 3/4 NPTS setting. Been doing
    that for years, and it works very well. Morad builds a Standard
    1"X14 to 3/4 Pipe Slip-over Adapter, with Setscrew locking, that works
    well, also.

    Bruce in alaska
  8. Howard

    Howard Guest

    I think I'm gonna just buy a whole new antenna and be done with it.
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