High SWR with magnet antenna

Discussion in 'CB Radio Forum' started by sly-fox, Jan 31, 2021.

  1. sly-fox

    sly-fox Bobtail Member

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    HEllo, Im fairly new to radio, and so, some of my friends and I put a K-30 (magnet) antenna on a steel plate drilled into the top of a tower made of 2/4s, connected through a small gap under my door (not crimping the coax, its a large enough gap I can easily slide the coax in and out of) connected to a Cobra 29 (powered by an 120V AC to 12VDC power supply), however, the issue is my SWR is above 3 on an swr meter I picked up. would anyone have any clue as to why?
     

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  3. Timin770

    Timin770 Road Train Member

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    I would think you'd need a very large steel plate to make it work. There are some really CB-smart dudes who post here, so hopefully they can weigh in
     
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  4. Crude Truckin'

    Crude Truckin' Alien Spacecraft

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    Not enough ground plane for that magnetic antenna I'd say. Just go buy a base station antenna and you'll have 10x the results of that magnetic. @rabbiporkchop
     
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  5. Crude Truckin'

    Crude Truckin' Alien Spacecraft

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    Is your swr 3:1 across all 40 channels?
     
  6. Crude Truckin'

    Crude Truckin' Alien Spacecraft

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    If you have a multimeter, also check impedance from center conductor to the shield on the coax. How long is the coax?
     
  7. Powder Joints

    Powder Joints Subjective Prognosticator

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    Sounds like a open shield, check the coax, also open the bottom (probably peeling the tape back) and check the connections at the base connector in the mount, if one of your friend soldered the PL on check it for a short/open also.
     
  8. Powder Joints

    Powder Joints Subjective Prognosticator

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    In general, make sure the coax is grounded to the antenna structure ( Oh yea you can't, its wood, hummmm) , it can use a mast or tower (if you had one) to reflect off although it will give it kind of a weird radiation pattern. Mount a 10' pipe to your wood to, wood is a terrible antenna structure. Cheep seldom works in radio, usually makes you spend twice. Buy once cry once, your 2x4's would make you a better radio bench, goto the Home Peepot and get a couple of 10 dollar masts.
    Im not telling you to go buy my 100' rohn tower, but a couple of tv antenna masts and a cheap ground plane from Ebate will help you tons.
     
    Last edited: Jan 31, 2021
  9. Ridgeline

    Ridgeline Road Train Member

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    A hillbilly antenna, haven’t heard one made in a long time.

    can’t do it with a magnet mount, just get something that you can mount to the plate, like a k40 trunk lip mount then take a 16 gauge wire, attach it to the plate then run it down to the 2x4 about 16 to 18 feet long. Your swr should drop.
     
  10. sly-fox

    sly-fox Bobtail Member

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    Jan 30, 2021
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    Thank you all for the replies, Ill try the mast/tower idea instead of the wood, and ya, all channels are above 3 swr, also IU checked with my meter, and the sheild on the coax is fine and the antenna is fine. Thank you. Ill reply back with results and such.
     
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