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  1. #1
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    Sep 2010
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    Default Magnetic base antenna with no ground

    I RECENTLY INSTALLED A 3 FOOT MAGNETIC ANTENNA. IT IS INSTALLED ON THE ROOF OF AN S10-BLAZER. I WAS CAREFUL TO EXTEND THE COAX TO MAXIMUM LENGTH AND AVOID BUNCHING UP OR COILING ON ITS WAY TO THE RADIO. THE ANTENNA HAS NO WAY TO GROUND ITSELF TO THE VEHICLE BODY AND MENTIONED NOTHING IN THE INSTRUCTIONS ABOUT GROUNDING. IT SITS ON A PLASTIC BASE WITH THE MAGNET FULLY INSULATED WITH PLASTIC. THE RADIO IS ACTING COMPLETLY DEAD. POWERS UP, CHANGES CHANNELS BUT WONT RECEIVE OR TRANSMIT ANYTHING. WHAT PART OF THE COAX SHOULD BE GROUNDED TO VEHICLE METAL ? THE OUTER JACKET OR THE CENTER CONDUCTOR ? IS THE BEST LOCATION FOR THE GROUND POINT AT THE BASE OF THE ANTENNA ? CAN I SIMPLY RUN A WIRE FROM THE RADIO CHASSIS TO VEHICLE METAL? DOES THIS EFFECT SWR ? HAS ANYONE BURNED OUT A RADIO WITH AN NON - GROUNDED ANTENNA ? WILL RUNNING A WIRE FROM THE ANTENNA WHIP TO GROUNDED SCREW IN THE ROOF SHEETMETAL FIX THIS PROBLEM ?

  2. #2
    Experienced
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    Jun 2011
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    Peoples Republic of NY
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    231

    Default Re: Magnetic base antenna with no ground

    There are several issues here. First off, almost everything affects swr. The shielding braid of the coax cable is ground. You don't need a ground but rather a ground plane for a mobile install to work. The flat sheet metal of the truck works as the ground plane providing the mirror image to make it work. A 3 foot antenna is very small and greatly compromised for CB. Nonetheless you should still receive a high noise level on CH19. There is more likely a break in the coax. If you have a factory pressed on PL259, cut it off and toss it in the trash. Buy a real one with an adapter and solder it on. If you want full on performance and your willing to drill..... get a heavy duty ball mount with a 96 inch fiberglass whip. Mount it at the rear d/s at least 1 ft higher than the bumper. You want little to no obstruction. Your swr will be 1:1 because the antenna is both electrically and physically correct.

  3. #3
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    Sep 2010
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    PHOENIX AZ
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    8

    Unhappy Re: Magnetic base antenna with no ground

    I HAVE A VANCO P/N PL259-5 RG58 PLUG . IT LOOKS LIKE I CAN SOLDER THE CENTER CONDUCTOR TO THE CENTER PIN AND SOLDER THE OUTER BRAIDED JACKET TO THE OUTER SHELL OF THE PL259. WHAT ADAPTER DO I NEED TO THROW OUT THE FACTORY PRESSED ON PLUG ? CAN I JUST SOLDER ON THE PL259 I HAVE NOW?
    SWITCHING TO A MUCH LONGER STAINLESS STEEL WHIP AS WELL. WILL CHECK SWR 2MORROW. PULLING OUT "DEAD" COBRA RADIO AND REPLACING WITH UNIDEN PRO538w.
    DOES THE FACT THAT THE ANTENNA BASE IS NOT TOUCHING THE SHEETMETAL OF THE TRUCK HAVE ANY EFFECT ON SWR / PERFORMANCE ETC...
    IS IT BETTER TO DRILL INTO THE HEAVIER STEEL OF THE REAR BUMPER TO ALLOW THE ANTENNA'S METAL BASE TO CONNECT TO THE VEHICLE METAL ??
    Attached Images Attached Images

  4. #4
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    Default Re: Magnetic base antenna with no ground

    What adapter do i need besides a pl259 connector ?

  5. #5
    Newcomer
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    Jul 2008
    Location
    South West, Western Australia
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    74

    Default Re: Magnetic base antenna with no ground

    You can get two main variations of the PL259 coax plug. see link below which explains the adaptor query
    PL259

    Also, you can get ground independant antennas, and these are generally noticeable as they have an integrated coil at the base of the antenna
    which creates a "magnetic" (for the want of a better word) ground plane. These antennas can be used where you may not be able to get a good
    flat surface on your vehicle to provide the "ground" for the antenna as dr_King explained.
    The "ground" for your radio is the negative of your power supply. also the body of the car (generally).
    The "ground" for your antenna isnt necessarily the metal of the vehicle (but can be) hence the insulation on your magnetic base.
    But thats only there to protect your paintwork

    Hope I haven't confused the issue.
    Last edited by johno_57; 12-09-2011 at 04:34 PM.

  6. #6
    Experienced
    Join Date
    Jun 2011
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    Peoples Republic of NY
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    231

    Default Re: Magnetic base antenna with no ground

    A standard PL259 is meant for RG 8 coax types which is thicker than the spagetti types for mobile install. The UG-175 goes over the Rg58 coax and screws into the PL259 making it nice and snug.

 

 

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