Antenna tuning question

Discussion in 'CB Radio Forum' started by dino360, Mar 2, 2014.

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  1. Mar 5, 2014 #11
    dino360

    dino360 Bobtail Member

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    I can run a couple extra grounds from the bed to frame, do you think the mount to frame ground is hurting it?
     
    dino360, Mar 5, 2014
    dino360, Mar 5, 2014
    #11
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  3. Mar 5, 2014 #12
    MsJamie

    MsJamie Road Train Member

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    That's because a 1/4 wavelength antenna tuned to resonance has a characteristic impedance of 37Ω, which will show up as a ~1.5:1 SWR on a 50Ω system. By reducing the resistance in the ground side of the antenna, it lowered the system impedance below 50Ω, which shows up as a slightly higher SWR.

    Even with the higher SWR, the antenna was operating with a higher efficiency, and was working better than before improving the ground.
     
    MsJamie, Mar 5, 2014
    MsJamie, Mar 5, 2014
    #12
  4. Mar 6, 2014 #13
    dino360

    dino360 Bobtail Member

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    So I'd be better off removing that ground wire? I was thinking of doing just that.
     
    dino360, Mar 6, 2014
    dino360, Mar 6, 2014
    #13
  5. Mar 6, 2014 #14
    jdchet

    jdchet Medium Load Member

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    One issue you may not have considered is your getting too much "reflect" from the cab of your pickup. An antenna must be in open air to achieve the best results SWR wise. Check out the link below.

    http://www.firestik.com/Tech_Docs/pickup.htm

    JD
     
    jdchet, Mar 6, 2014
    jdchet, Mar 6, 2014
    #14
  7. Mar 6, 2014 #15
    Picklechips

    Picklechips Light Load Member

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    Is this a Ford?
     
    Picklechips, Mar 6, 2014
    Picklechips, Mar 6, 2014
    #15
  8. Mar 6, 2014 #16
    Picklechips

    Picklechips Light Load Member

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    Oh is your coax all coiled up?
     
    Picklechips, Mar 6, 2014
    Picklechips, Mar 6, 2014
    #16
  9. Mar 7, 2014 #17
    dino360

    dino360 Bobtail Member

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    It is a Ford Ranger and no my coax isn't coiled up I ran it around the bed and back into the cab.
     
    dino360, Mar 7, 2014
    dino360, Mar 7, 2014
    #17
  10. Mar 7, 2014 #18
    Picklechips

    Picklechips Light Load Member

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    Is the body rubber mounted? If so ground everything. Hood to fenders doors to body ect.
     
    Picklechips, Mar 7, 2014
    Picklechips, Mar 7, 2014
    #18
  11. Mar 8, 2014 #19
    MsJamie

    MsJamie Road Train Member

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    No. 1.7:1 is fine. Your antenna is operating more efficiently, even at the slightly higher SWR. You may be losing a couple of percent of your signal due to the SWR, but you are more than making up for it with lower ground loss.
     
    MsJamie, Mar 8, 2014
    MsJamie, Mar 8, 2014
    #19
  12. Mar 9, 2014 #20
    dino360

    dino360 Bobtail Member

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    Thanks for all the replies. The SWR is in the acceptable range, I like the way the radio sounds and I'm able to talk with both trucks about 10 miles from one side of town to the other. I think I'll leave it as is until I get the tool box next week for that ranger and move the antenna. I'm thinking of mounting it center of the box which will move it away from the cab about 2ft or so and hopefully get less reflection from the cab.
     
    dino360, Mar 9, 2014
    dino360, Mar 9, 2014
    #20
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