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SWR Question on new radio.

Discussion in 'CB and Export Equipment and Accessories' started by Mudduckmobile, Dec 7, 2017.

  1. Mudduckmobile

    Mudduckmobile
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    My base antenna is good, coax, and two other radios work fine. swr is 1.0 on 27.385 R=63, X=0 with MFJ259c.
    But the new radio...on AM my swr is 1.2 and on SSB when sending out a two tone sound the swr is 2.5
    When I tx with my old radio (Optima mk3 and dx500 ) my swr is 1.3 max.
    New radio came from Bobs cb. I sent them an email and am hoping they get back to me soon. I paid with pay pal so it wont get to bad I hope.
    Any thoughts?
    Thank you.


     
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  2. camaro1

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    swr is good on the mfj so the new radio is probly sending out some harmonics not on 27mhz that the swr meter is picking up
     
  3. Mudduckmobile

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    I was hoping it was something easy to fix. I emailed Bobs, I hope to hear from them tomorrow, and I will bring your thought up. Eather they make it right or I need my $ back.
    Thank you\ for your help.
     
  4. Tallman

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    First thought is not to check SWR with SSB. If your AM SWR is good then the rest is good too. You are adjusting to a frequency not a transmit mode.
    To be honest I have never even heard of any body check SWR with SSB. If you did not
    re-calibrate on SSB that would explain why the SSB SWR is double of the AM reading.
     
  5. 9C1Driver

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    On AM the new radio is 1.2 your good to go. Bob's will tell you to stop trying to check your SWR on SSB. Problem solved, I don't see where there is anything to fix really.
     
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  6. Road Squawker

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    isn't the frequency on AM and SSB the same?

    I often inject a single tone into my rig and check the VSWR and/or ALC on SSB.

    Post # 2 is correct.

    Wanna bet that "certain" coils have been spread out?
     
  7. Tallman

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    Not 100 % correct. The AM signal would contain the carrier wave, SSB frequency is the carrier wave plus the audio information. SSB will not have a carrier wave if tuned properly. Let's say 27.185 MHz and add 1 kHz audio, the frequency transmitted would be 27.186 MHz upper sideband with no carrier wave.
    Still not a good idea to check SWR with the SSB.

    If the radio has had the magic power tune, yes the coils have been deformed.
     
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  8. Tallman

    Tallman
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    Ask if they checked the third harmonics level after "Adjusting" the radio.
     
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  9. Road Squawker

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    Thats' what the CAL function does.

    The meter doesn't know if it is on 27.185 or 27.186. It only knows that it has been CALibrated.

    There isn't anything "magic" about using unmodulated AM to check VSWR, compared to a CW tone, or RTTY tone, or SSB tone.
     
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  10. Tallman

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    The best and most commonly accepted method of SWR checking with a radio is AM unmodulated carrier wave. Be it unmodulated CW/RTTY/AM/FM, SSB does not qualify since there is not output without modulation. Modulation is a variable you don't want to introduce into SWR checking. Has the microphone gain been bumped, injected signal level changed, Frequency of modulation changed, ad nauseam. Can we agree to disagree?
     
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  11. Road Squawker

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    Sure, but I'm right [​IMG]

    I think you are missing the point about the usage of unmodulated AM for CALibration/VSWR monitoring, it has nothing to do with the MODE, it's all about using a constant input.
    Try setting the VSWR in the AM mode while talking.;)

    When I inject a constant 1 Kc tone into the audio chain, there is no variance in the audio frequency. .

    I was kinda waiting on you to tell the OP to NOT use a two tone signal in the SSB mode, as that will alter the meter reading.
     
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  12. tba02

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    Doesn't R=63, X (J) = 0 work out to be 1.26?
     
  13. Tallman

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    But you failed to comprehend what I wrote: "The best and most commonly accepted method of SWR checking with a radio is AM unmodulated carrier wave."
    Please keep your shorts up por favor.
     
    #13 Tallman, Dec 7, 2017
    Last edited: Dec 7, 2017
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  14. Tallman

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    Read post number four.
     
  15. rabbiporkchop

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    Without the proper test equipment and the knowledge to use it he won't be able to improve it.
    I'd try to see if he would be willing to swap it out with an unmolested radio.
     
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