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Does SWR Change w/Vehicle

Discussion in 'Ham Radio - CB - Trail Communications' started by Sandy, October 9, 2002.

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    1. Sandy

      Sandy Well-Known Member

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      :chug: :chug:

      Let's start with a cool one or two.

      Now, the question is:

      If using the same radio and antenna, does the SWR change going from an SUV to a pickup ?

      Why ?

      Thanks,
       
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    3. Rick

      Rick Pumpkin Pilot Staff Member Admin Elite Explorer

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      I suppose it could since the ground plane isn't exactly the same and neither is the conductivity to ground.
       
    4. Alec

      Alec Elite Moderator Moderator Emeritus

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      Yes!

      Like Rick said, ground. It also varies with the surfaces that the antenna is mounted to: hood, bumper, roof. The signal is directed by various surfaces and this screws with the settings.

      Am I right, or does this not have anything to do with SWR?
       
    5. Doug

      Doug I'm Awesome! Moderator Emeritus

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      Alec youre right. Where the antenna is placed on a vehicle does make a difference. It also depends on the antenna. Ive got a K40 k30 which is supposed to have a constant swr over all 40 channels. (I havent checked i set it on channel 20 and leave it.) The best place to mount an antenna is on the roof since the roof acts as a ground plane for the antenna. If you put the antenna on the bumper it wouldnt work quite as well and it would most likely affect the swr.
       
    6. tmanson

      tmanson Elite Explorer

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      As the environment around the antenna changes the SWR will change. Going from a pickup roof where the antenna environment is air on top and a 5x4ft ground plane below compared to an X, that would be air and a 5x10ft ground plane. The closer to the antenna the greater effect. There would be less change going from the center of an X to the center of an Expedition’s roof compared to the pickup to X. Going from the bumper (ground plane and air next to the antenna) to the roof would be the biggest change. Even though the mounting location effects the antenna SWR I would expect the change to me minimal. That is why people can get away with buying an antenna, hooking it up and using it without checking the SWR. The big change would happen if you changed the air in the equation.

      I am really not a super radio geek, only an average one, I just deal with antennas daily at work.

      :chug:
       
    7. Sandy

      Sandy Well-Known Member

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      Thanks for the info.
      Appears that everyone is thinking the same.

      :usa: :chug: :ca:
       

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