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any one use a dual antenna setup?

Discussion in 'Communication (CB | GPS | HAM)' started by bryguy00b, Mar 29, 2003.

  1. bryguy00b

    bryguy00b 3/4 ton status

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    i was wondering about this..i want to run this setup..(more for looks realy) but i still want it to be functional. it does not have to be great..i just want something to use on trails and to play around with..but i love the way dual antennas look..like moutned on the mirrors..
     
  2. Dale fan

    Dale fan 1/2 ton status

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    You would be better off running one real antenna and one "dummy" antenna if you want the looks. There are a few posts here that discuss the disadvantages of running dual antennas. Mainly your vehicle isn't wide enough for it to work properly.
     
  3. Ddragggon

    Ddragggon 1/2 ton status

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    in order for Dual antennas to work optimaly, they need to be mounted 1/4(?) of a CB carrier wave apaprt... this happens to be about 9 feet. they also need to be tuned to eachother, which can be hard to do, but once you do, you'll have unparalelled reception and sending capabilities, with one exception: they'll only work in a strait line. whoever you want to talk to will have to be either in front of you, or behind you. most everything else will be canceled out, and dead.

    I've been planning on running 3 antenna's on my burb... Dual antennas for straitline, and a 3rd antenna ( through a switchbox) for a single antenna mounted on the top middle of my roof.

    I'm going to double check my CB information, and change my facts as needed...

    -Rich

    Edit: off a CB bulletin board...

    [ QUOTE ]
    In order for the Co-Phased antennas to work properly, they must be spaced 1/4 wavelength apart in order to achieve the enlongated figure eight radiation pattern.
    This would mean at 27.255 mhz (mid band) you would have to have them spaced 8.58 feet apart.
    (234 divided by 27.255 equals 8.58)
    If they are spaced closer than this, it will actually deform the radiation pattern, and will detract rather than enhance the signal.
    I recommend a single whip antenna, which should give you sufficient coverage with your CB.
    Bill

    [/ QUOTE ](rest of the article here)
     
  4. bryguy00b

    bryguy00b 3/4 ton status

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    well id rather just have one if i really cant make it work..i dont want anything unfunctional on my truck..
     
  5. big83chevy4x4

    big83chevy4x4 3/4 ton status

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    you could have one hooked to the cb and the other hooked to the radio. then you wouldn't have anything non-fuctional on your truck
     
  6. bigblock454

    bigblock454 Clack Clack Clack Premium Member

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    I have duals at 5' spread, works great.
     
  7. bryguy00b

    bryguy00b 3/4 ton status

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    i thought the trucks werent wide enough
     
  8. rebelk5frk

    rebelk5frk 1/2 ton status

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    Our trucks aren't wide enough to make dual's work "properly" but they can be made to work.

    I once had an S-10 with duals mounted inside the bed rails and it worked ok.

    The problem is yes you can tune them to work and not blow up your radio but the radiation pattern from a dual antenna setup that is spaced too close together will be a lot more directional and weirdly shaped than it should be.

    When you space them at a quarter wavelength apart (about 9 feet for cb band) they counteract the odd shape of the groundplane (vehicle body) and make a more uniform omnidirectional pattern. The closer they are from what they should be the funkier the pattern looks. After a point they will work against each other and cause a star burst type of pattern of dead spots and somewhat higher gain areas spread all over the place.
     
  9. 88Silverado

    88Silverado 1/2 ton status

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    With two 1/4 wave antennas spaced 1/4 wave apart (8.5-9.0 feet)apart and fed "in-phase" you will get about 1.1dB of gain. (remember, when you split the signal to feed each antenna, you cut the power to each antenna in half) This equates to virtually nothing in your receiver. The sides will only be down 3dB. Not worth the effort.
    If you can separate the antennas 1/2 wave (18 feet) and feed 180 degrees out of phase, you will get about 3.6dB of gain (1/2 S-unit increase) (Properly calibrated S-meters should be 6dB per S-unit but ive seen 2dB S-unit radios)

    The pattern and gain are "Theoretical" and in most installations (antennas mounted on mirrors) are no where close to the actual pattern due to current distribution and return losses. You would have better luck running a single antenna with a linear.

    Theres nothing for free and no magic when it comes to antennas. The biggest performance hits with verticals are ground losses. If you make gain in one area, you loose it in another. A good representation of antenna patterns is to squeeze a balloon. You squeeze it in one place, the displaced air (energy) goes somewhere else. Nothing has been added to it, just relocated.
     

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