Vr6 adjustment? Cobra 29LX

Discussion in 'CB Radio Forum' started by Chris M., Oct 2, 2020.

  1. Chris M.

    Chris M. Light Load Member

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    So I’m scratching my head on this one. My little cobra 18 finally left town. So pickup up a cobra 29LX. Nice radio. Here is what is wonky

    I drive a 387 Pete. Not the greatest truck for cb. Now I have a new coax and laid the excess out......I’m getting perfect swr readings.....I went from a 4ft antenna to a 2 ft antenna. Identical reading. Only thing I do get is the antenna warning that pops up IF my dynamic is over half and if my frequency tuner knob is cranks to the right. Any ideas? I’ve heard this is a ground issue to the radio, I’ve heard vr6 is too sensitive so you adjust it. Any clarification would be great cause right now I feel like I just accomplished the impossible but with a red light.....
     
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  3. Night Stalker10

    Night Stalker10 Heavy Load Member

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    Ditch the 2 ft antenna and use the 4 ft antenna.
     
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  4. Chris M.

    Chris M. Light Load Member

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    I agree completely but I get the same results far as the antenna warning......I had an extra to see if my results would change and they did not which is why I am confused. And I have great swr readings....
     
  5. Night Stalker10

    Night Stalker10 Heavy Load Member

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    Okay, it's not uncommon for the 29's antenna warning indicator to be out of adjustment. What you need to do is unplug the coax from the radio, and remove the bottom cover. With the radio on, key the Mike and turn vr6 until the words "ANTENNA WARNING" just turns off, then turn vr6 the other direction until the words "ANTENNA WARNING" comes back on, and then stop adjusting the pot. Reinstall the radios cover, and re-connect coax. This should solve your problem. Don't worry, you won't hurt the radio to key it up for a few seconds with no antenna connected. Also use an external swr meter, the radio's internal swr meter is worthless. My company bought 2 of these cobra lx radios, and the radios internal swr meters showed an swr of 1.2. The antenna on the truck was bad, and my antenna analyzer showed an swr of 5.1.
     
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  6. Ridgeline

    Ridgeline Road Train Member

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    Wait!

    did you check the swr with an external meter?
     
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  7. Chris M.

    Chris M. Light Load Member

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    No I’m not home.. usually I can tell even from the stock radio one. It was tuned for the old radio so had to be close. I’ve never had that much difference between my old 29 in a different truck and my meter. Just saying.
     
  8. Chris M.

    Chris M. Light Load Member

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    I’ve got new 18ft coax and a plug to the antenna. Like 2 months ago. Power wires are good to the radio. I had to redo those awhile ago.
     
  9. Night Stalker10

    Night Stalker10 Heavy Load Member

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    If your antenna system is properly adjusted, it shouldn't matter when switching radios. SWR should remain the same. You do need to use an external SWR meter to check your antenna, like I mentioned earlier. As far as adjusting the SWR vr6 pot in the Cobra 29, the method I told you is an approved method by cobra, if you don't have a 150 ohm dummy load.
     
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  10. craig_sez

    craig_sez Road Train Member

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    Get your multi meter out and test how well the ant is rf grounded..
    Between fibreglass and plastic bushings n washers it can still create issues..
     
  11. Ridgeline

    Ridgeline Road Train Member

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    Craig, you ok?

    you can not test an rf ground with a multi meter.
     
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