Another swr question

Discussion in 'CB Radio Forum' started by KAK, Nov 25, 2012.

  1. KAK

    KAK Medium Load Member

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    I know the swr meter in the radio's are not very accurate. When I check with an external meter I am getting 2.s and 2.5's on the external and the same on the radio meter. I unhook the external and only get 1:3 to 1:4 on the radio meter. Is my external meter giving me a high swr or should I trust it ??

    THANKS
     
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  3. Mt Airy

    Mt Airy Light Load Member

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    I have almost the same radio is you and I checked mine with a external meter both were the same . Did you calibrate the external meter ?
     
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  4. Turbo-T

    Turbo-T Road Train Member

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    X2...also the internal meter has an adjustment on it that will read incorrectly if incorrectly adjusted.
     
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  5. MsJamie

    MsJamie Road Train Member

    Out of curiosity, how long is the cable between your radio and SWR meter?
     
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  6. KAK

    KAK Medium Load Member

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    External calibrated, not sure how to calibrate the internal. 3 ft on my jumper cable. Just not sure why it is changing on the internal meter with the external meter hooked up vs not hooked up.

    You have to remember I know just enough to be dangerous and mess things up :biggrin_25523:
     
  7. MsJamie

    MsJamie Road Train Member

    The coax in your setup is acting as an impedance matching network. Adding the extra coax is upsetting that match. I bet that if you coiled up a few feet of that coax and measured again, the SWR would change.

    The proper place to check SWR is right at the antenna. Any other place has the coax influencing the reading.
     
  8. KAK

    KAK Medium Load Member

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    So how do I go about checking at the antenna ? Run a long jumper from the radio out to the meter and a short one to the antenna ??
     
  9. Powder Joints

    Powder Joints Subjective Prognosticator

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    Actually I find the internal SWR bridge to be just fine, only if some screwdriver jockey has been in there to mess it up. I find about a 3 foot jumper works fine.
     
  10. MsJamie

    MsJamie Road Train Member

    Pretty much. If your antenna has a PL-259 connection at the antenna, you can use the existing coax. I use a short (6") jumper between the meter and antenna.

    To be honest, since the internal and external meters agree, I would just trust the internal meter on the regular coax. <1.5:1 is fine.

    It just occurred to me that your jumper coax may be bad, as well.
     
  11. twolane

    twolane Medium Load Member

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    I'd never contradict MsJamie but here is my experience...

    I've noticed that alot of drivers believe that they can adjust the swr with with the calibration knob on their radio or meter. This is not true!

    For those of ya that may not know...here's the drill for checking swr no matter internal or external meter.

    I go to ch. 20 initally.
    Find the switch that lets you choose "calibrate", key the mic. and hold it keyed, while you adjust the "calibrate" KNOB until the meter reads AT the calibrate pointer at the top rhs of the meter. Release the key & choose SWR at the switch. Don't touch that knob! Key the mic and see the meter. The LESS it moves the better. The calibrate knob does not change anything. It only "calibrates" the meter.

    Maybe MsJamie can explain this better but that calibrate KNOB doesn't change anything!
     
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