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Need help with resonance algebra

Discussion in 'Mathematics and Physics' started by cyb0rg777, Apr 15, 2007.

  1. cyb0rg777

    cyb0rg777 New Member

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    I was figuring up some resonant circuits.
    I haven't had time to learn latex very well so I'll try to do the best I can.
    So I started with this resonant formula.



    I found the value for L with a 20pf capacitor at 440mhz by changing it to this formula.



    Now I'm looking for how many turns of an air core inductor I need to make a 6.5419nH coil with a diameter of 3.175mm(.125") and 12.7mm(.5") length.

    I'm starting with this formula.



    L= inductance in henries
    r=radius in meters
    l=length in meters
    N= number of turns

    So I rearranged it to this to get the number of turns.



    But when I check my answer it comes out wrong. :(
    Could you help me out ?
    My math is not very good.
     
    Last edited: Apr 15, 2007
  2. cyb0rg777

    cyb0rg777 New Member

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    I think I got it .
    I might have been forgetting to take the square root on the last formula.
    It comes up to 1.6 turns .I think I'll try it with a smaller capacitor to get more turns.
     
  3. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Assuming you're hoping to construct such a coil?, you need to be aware that stray capacitance and inductance will completely change your calculations!.
     
  4. dave

    Dave New Member

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  5. cyb0rg777

    cyb0rg777 New Member

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    I was hoping to adjust the coils by spreading them apart and squeezing them together but I've never built anything like that from scratch.From following a set of instructions yes but not from my own design.
     
  6. Hero999

    Hero999 Banned

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    Spread apart is often best because it will keep the parasitic capacitance as low a as possible and a long and thin coil is supposed to be better than a long a short and fat coil.
     

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