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Ball Mount For CB Antenna

Discussion in 'Communication (CB | GPS | HAM)' started by Polaris, Sep 8, 2003.

  1. Polaris

    Polaris 1/2 ton status

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    I have this on my Blazer. I like the idea of no wires running outside. I have the coax ran along my roll cage and most of it is in wire loom. When I drilled the big honkin' hole in my quarter panel, the 3 supplied screws (one of which is the ground) that holds the whole works together was too small, due to the double walled quarter panel. I just went & bought new screws that were longer. However, things aren't working. It worked ok for a little while. It squeals really bad now. I can hear people just fine but when I transmit, it squeals. When I use a different antenna it works fine too. Those of you who have a ball mount, how did you do it? Are you pleased with the performance? Now I have all these holes drilled into the truck & a poseur antenna! /forums/images/graemlins/1zhelp.gif
     
  2. HarryH3

    HarryH3 1 ton status Author

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    Look closely at the mount. It should have four screws. Mine uses 3 to hold the mount in place and then has a small, sharp set screw that gouges into the sheet metal to provide a good ground. If you didn't install that one, then it's possible that the ground is flaky.
     
  3. Polaris

    Polaris 1/2 ton status

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    Here's a picture of mine:
    [​IMG]
    There are little square tabs that go in between the screws. Behind that is a rubber gasket. According to the instructions, the outer, braided part of the wire goes to any of the small screws and the center core is screwed onto the thing in the middle. Yet, it works for crap!
     
  4. HarryH3

    HarryH3 1 ton status Author

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    Hmm, mine has one extra hole drilled in that large washer looking piece. The hole is threaded and has the set screw in it to make sure that the antenna is always grounded.
     
  5. 88Silverado

    88Silverado 1/2 ton status

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    You have the mount wired up correctly.
    If you can, check for a short between the center conductor and the shield at the radio end of the cable.

    I cant understand how you would get a squeal from the antenna. Did you check the SWR??

    Sounds like you are getting feedback from a speaker into the mic. If you move the mic away from the radio does the squeal stop?

    Interesting /forums/images/graemlins/thinking.gif
     
  6. rebelk5frk

    rebelk5frk 1/2 ton status

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    [ QUOTE ]
    There are little square tabs that go in between the screws. Behind that is a rubber gasket

    [/ QUOTE ]

    I might not be reading this right but it doesn't sound right.

    The squeal you're hearing and/or transmitting is probably your antenna. It's normally caused by a bad RF ground.

    The ball mount should have 4 main peices you need to worry about.
    Starting from the top:
    1) The ball
    2) Thick insulating plate
    3) Rubber gasket
    -----Roof/body panel-----
    4) Metal plate

    For best contact of the ground you should take off the paint on the inside area of the roof that the metal grounding plate is touching.

    Also the large bolt and nut that comes though the roof from the ball should not be touching any metal at all except for the center conductor of the coax.

    Good luck.
     
  7. rebelk5frk

    rebelk5frk 1/2 ton status

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    [ QUOTE ]
    When I drilled the big honkin' hole in my quarter panel, the 3 supplied screws (one of which is the ground) that holds the whole works together was too small, due to the double walled quarter panel

    [/ QUOTE ]

    I just noticed this part....

    If I understand right from the picture and what you said, you have it mounted pretty high on the quarter panel where the outer panel is a couple of inches from the inner panel.
    You shouldn't bolt it through both panels. You will not be able to keep it tight enough to keep a decent ground. You should probably take the 3 nuts off and expand the holes on the interior panel large enough to tighten the nuts to the exterior panel. Getting the grounding plate in that tight area might be tricky but would make for a much more solid mount in the end.

    When it's all working right, use some silicone caulk to seal everything up to prevent rust and keep water out. Using the silicone to fill the holes inside works great and is easy to remove to access the screws if needed.

    BTW I have a ball mount on my old car that has served me well for several years with no problems. Those big ball mounts are one of the best ways to mount an antenna when it's done right.
     
  8. 88Silverado

    88Silverado 1/2 ton status

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    I would think that would require a very bad RF ground like the shield is floating at the end antenna end (might be if the screws dont touch metal going thru the panels, the outer plate didnt cut thru the paint and the back plate has a rubber gasket between it and the body) the outer part of the shield is going have common-mode return currents back to the radio. If thats the case it should show a high SWR when checked and moving the mic away from the cable should make it better. Were not talking very large currents here with 4 watts.

    A simple test would be to move the shield lug from the mounting plate and grounding it directly to the body panel. If its a bad RF ground, that will be much better.

    Wondering if they have a gain type of mic and its cranked wide open ?
     
  9. rebelk5frk

    rebelk5frk 1/2 ton status

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    [ QUOTE ]
    If thats the case it should show a high SWR when checked and moving the mic away from the cable should make it better.

    [/ QUOTE ]

    A high SWR isn't always shown with poor RF grounds though. She hasn't mentioned anything about testing the SWR. More than likely if it is a bad ground then yeah the SWR will be on the high side. I've had it show almost flat when testing with a meter but when modulated the extra 8+ watts from the audio is enough make the bad ground a problem and start to squeal.

    [ QUOTE ]
    Wondering if they have a gain type of mic and its cranked wide open

    [/ QUOTE ]
    Just guessing but I don't think she has a power mic. From what I understand of the way it's mounted, I think it has worked itself loose and causing a bad ground. It sounds like she has it mounted through 2 seperate panels that would flex and loosen over time [she did say it worked at first]
     
  10. Polaris

    Polaris 1/2 ton status

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    Hi and thanks everyone for the help. I'll tinker with it some today when I need a break from shaving the rear axle /forums/images/graemlins/cool.gif. I do not know anyone with an SWR meter. I don't think I have a power mic. It's just a basic unit with the part you depress to talk. The squealing is not heard by me when I talk. That is just how everyone else hears me. Like I said, I receive just fine too. I suspect I need to make a larger hole on the interior of the quarter panel and mount it down tight like it's supposed to be, without the gap.
     
  11. Polaris

    Polaris 1/2 ton status

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    Good news! I think it's fixed. At least, my neighbor could hear me loud & clear when we tested it this afternoon. No more squealing. I had the rubber gasket in the wrong spot /forums/images/graemlins/blush.gif. We'll see how it does this weekend, but I think the problem is solved. I was afraid I'd have a bunch of holes in the side of my truck for no reason. Thanks so much for your help!
     
  12. rebelk5frk

    rebelk5frk 1/2 ton status

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    /forums/images/graemlins/thumb.gif /forums/images/graemlins/thumb.gif /forums/images/graemlins/thumb.gif Glad to hear it's working now.
     
  13. 88Silverado

    88Silverado 1/2 ton status

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    I guess I didnt understand where the squealing was.
    I thought you were hearing it out of the radio and it was being coupled into the mic.

    If the gasket was on the wrong side, it sounds like the shield wasnt terminated to ground, thus causing lots of stray RF.

    RebelK5 is really good at this stuff /forums/images/graemlins/thumb.gif
     
  14. Polaris

    Polaris 1/2 ton status

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    I should have been more specific. It will be put to the test this weekend /forums/images/graemlins/thumb.gif

    You are right, RebelK5 is very good at this. Kudos!
     
  15. Z3PR

    Z3PR Banned

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    Chech the center post where the coax hooks up. Make sure there is no metal making contact with center. Also check that the center wire isn't making contact with shield wire. Sounds to me like a direct ground in the coax, or mount.
     
  16. Polaris

    Polaris 1/2 ton status

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    Thanks, but it's all fixed now. It worked great over the weekend /forums/images/graemlins/smile.gif
     
  17. Z3PR

    Z3PR Banned

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    Kewl, so what was wrong with it ??
     
  18. rebelk5frk

    rebelk5frk 1/2 ton status

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    [ QUOTE ]
    I had the rubber gasket in the wrong spot

    [/ QUOTE ]

    See what happens when you read the whole thread /forums/images/graemlins/grin.gif /forums/images/graemlins/rotfl.gif
     
  19. Z3PR

    Z3PR Banned

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    K, I missed that. And yes, I did read the whole thread.
     

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