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High SWR Into DX1600

Discussion in 'General CB Services Discussion' started by Centauri, Dec 30, 2015.

  1. Centauri

    Centauri Member

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    Hoping someone can tell me how to match my 29 Cobra into the Sweet Sixteen. SWR is running better than 7 when keying the box with 4 watts from radio using 9 foot jumper, and pegs the meter with 3 foot jumper.. Antenna is running 1.2 SWR. It seems like using a longer jumper from radio to 1600 is just masking some other problem. Thanks for any help.


     

  2. Tallman

    Tallman W9WDX Amateur Radio Member, KW4YJ EXTRA class

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    Sounds like you might have a bad jumper. The SWR is rarely that bad unless the amp is toasted.
     
  3. Centauri

    Centauri Member

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    All combiners resistors and other parts look good, getting a 300 dk out with 4 in. That's why I'm confused at SWR's.
     
  4. Robb

    Robb Yup

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    Has the radio been so peaked that it is throwing off strong harmonics (freqs not on 27mhz)?
    Common problem for poor tuning.
    Might want to retune it - to be sure that it isn't the problem.
     
    midnight special likes this.
  5. fodendaf

    fodendaf Active Member

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    that output seems far too high for an amp without a driver. unless there are oscillations that amp shouldnt deadkey more than 80w with 4w input.
     
    543_Dallas likes this.
  6. Centauri

    Centauri Member

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    That could be a problem too. It's an older 29 and probably should have it re tuned. Wouldn't hurt anyway.
     
  7. Centauri

    Centauri Member

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    It's grounded and the trucks grounded the hilt everywhere so I don't know why it would be oscillating or where it would be coming from. Unless it doesn't like being close to the radio.
     
  8. fodendaf

    fodendaf Active Member

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    Well if you keep using it you'll have an expensive repair bill on your hands.
     
  9. 543_Dallas

    543_Dallas Sr. Member

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    How is the SWR between the amp and antenna with the amp on? If something is wrong with the amplifier and oscillation is the problem the swr to the antenna will likely be high with the amp on. Having a proper install with good grounds will not correct this. If you are using rg8 or 213 try a 6 or 12 ft jumper between the radio and amp to see if it plays nice.

    It does sound like oscillation which isn't uncommon for a CB amp and may be in part due to the low carrier you are driving it with. Using a driver and bringing the drive up may make it stop. When you get to that point the swr and output will drop or the relay might stick and blow a couple of pills before you disconnect the power. It would be best to have someone experienced check it out though.
     
    tba02 likes this.
  10. Centauri

    Centauri Member

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    Ok this is what I found so far. The SWR meter I was using between the radio and Amp was bad. Used a different meter and SWR is 1.1 with 6' jumper from radio to amp when keying. Antenna SWR is 1.2 with box on, but still showing DK of 2-300. Gotta figure that one out. It may be a meter issue too.
     
  11. Centauri

    Centauri Member

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    The low carrier was definitely part of the problem among a few. Replaced all RG8 coax with LMR400, 1 meter, and am driving with 12 watt dk swinging 30 from a mod v plus I found at a local CB shop. All's good now. Thanks for the help.
     
    tba02 likes this.

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