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swr problem 4104 beams

Discussion in 'CB Antennas' started by nosratt, Mar 5, 2011.

  1. nosratt

    nosratt Member

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    I have a set of Shakespeare 4104 4 element beams...
    they have no Gama adjustment ...
    Swr goes over 2.0 @ 27mz and up from there.
    Fiberglass 18' boom and fiberglass elements ...
    Have anybody heard of beams how to Shuster them...
    Any help can't hurt
    Thanks


     
    #1
  2. RatsoW8

    RatsoW8 Supporting Member

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    If the antenna has telescoping elements I'm guessing you need to lengthen the elements slightly. Can you tell where antenna is resonant?

    Also, what is "Shuster"..not an antenna term I'm familiar with.
     
    #2
  3. nosratt

    nosratt Member

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    update to 4104 swr saga

    I was wondering how to set swr on the 4104 beam...
    Have moved front and rear elements but doesn't seem to change
    Help... thanks
     
    #3
  4. nosratt

    nosratt Member

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    shuster?

    Not an antenna term... a fat finger moment. Sorry...
    I think I was trying to say was ajust the swr.
    also elements are one piece fiberglass...
    Am I wasting my time?
     
    #4
  5. RatsoW8

    RatsoW8 Supporting Member

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    How does the feedline attach to the antenna and are you using balun? Pretty sure you need to start tuning with the driven element. Hopefully you have or have access to an antenna analyzer so you can see where it IS tuned so you have a starting point.

    Also measure the reflector, driven element and one of the directors end to end and post the lengths in inches.
     
    #5
  6. Henry HPSD

    Henry HPSD Well-Known Member

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    indeed, element length from tip to tip including diamter and element distance would help.
    a picture of the entire antenna and one detailed one of the feedpoint is appriciated aswell.

    Thats the info wich is needed, from there we can help.

    kind regards,

    Henry
    All about antennas
     
    #6
  7. nosratt

    nosratt Member

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    4104 element measurements ...

    #1 191"
    #2 183" driver. With transmission line on it
    #3 179"
    #4 171"
    boom 188 1/2"
    distance between #1 and #2. 68. 3/4"
    between #2 and center of boom 22 1/2"
    between #2 and #3 55 1/2"
    between #3 and #4 61 3/4"
    The elements are two piece fiberglass with a steel threaded ends
    The transmission/coax is attached to #2 element by splitting the coax and an eyelet put on the center lead and on shield attached to the top and bottom of #2 element
    On #1 element is grounded between the top and bottom element
    How do I set standing wave thanks
     
    #7
  8. RatsoW8

    RatsoW8 Supporting Member

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    Someone can check this math but it looks like your antenna is cut to operate at about 30 mhz. Sorry to tell you but this is no where close to where you need it to operate so you can't set the swr on it. Curious where you got it and who was using it before you.

    Here are some approximate lenghts for a yagi with a center freq of 27.185 (channel 19). You would need to lengthen all of the elements significantly to bring the resonant freq. down to center it on the CB channels.

    Reflector - 18' 5.5" or 221"
    Driven Element - 17' 4" or 208"
    Director 1, etc - 16' 4.5" or 196.5"
     
    #8
  9. nosratt

    nosratt Member

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    4104 swr right now...

    26.165 / 1.1
    26.365 / 1.4
    26.565 / 1.7
    26.905 / 1.9
    27.045 / 2.1
    Help?
     
    #9
  10. Marconi

    Marconi Supporting Member

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    Where is this antenna supposed to be resonant?

    How long are the 1/2 elements?

    How did you do the spacing?

    the AT is very narrow banded, just a bit over the CB bandwidth.
     
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  11. Robb

    Robb Yup

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    Check your beam dimensions against this antenna. Not only the element lengths; but the spacing between the elements as well. Make it as exact as possible! If you us this as a guide, it should tune the center frequency to 27.555.
    Makes it most effective this way - IMO . . .

    The Ultimate Guide to 11 Meter CB Antennas
     
    #11
    Last edited: Mar 6, 2011
  12. nosratt

    nosratt Member

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    4104 1/2 element

    #1 95"
    #2 91"
    #3 89"
    #4 85"
     
    #12
  13. Robb

    Robb Yup

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    Like this:

    [​IMG]
     
    #13
    Last edited: Mar 6, 2011
  14. RatsoW8

    RatsoW8 Supporting Member

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    Ok, I'm stumped. Loooking at the swr readings you eneed to make the elements shorter. The lower the freq the longer the elements and visa versa.
     
    #14
  15. Robb

    Robb Yup

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    Agreed!
     
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