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Re: Conical Secondary




>
> Original Poster: "Jason R. Johnson" <hvjjohnson13-at-xoommail-dot-com>

Hi Jason, 

I'm copying a post at the bottom. It is a post back in August of 98 that Bert
Hickman sent to Dave Sharp. May have what your looking for. View with fixed
width font. 
Bart 
>
> Does any body have any calculations for a conical secondary 
> (frequency, inductance, etc.) because I've got a tube that 
> starts out -at- 2 5/8 in. and over 11 1/2 in. tapers to 1 1/8 
> in. and I thought that it would look pretty cool on one of 
> my tiny (1 7/8 x 6 3/4in) coils. 
>
> Jason Johnson



--------------------------------------------------------------------- 
Hope this is what you're looking for. Included are Archimedes, helical, 
and inverse conical primaries. The helical and Archimedes forms are from 
Wheeler, and the inverse conical is a hybrid form that appropriately 
weights the vertical and horizontal components of Helical and Archimedes 
inductances. 

All dimensions are in inches, and L is in microHenries. While the 
Inverse Conical calculation is a little "hairier" than the first two, 
it's relatively easy to calculate for any desired angle, especially if 
set up in a spreadsheet. 
------------------------------------------------------------------------ 
Case 1: Archimedes Spiral (Flat): 

          Let R = Ave Radius 
              N = Number of Turns 
              w = Width of Winding 
  

           |   R    |      N Turns 
      o o o o o o   |   o o o o o o 
      |    W    |   | 
  

     L = (R^2)*(N^2)/(8*R+11*W)   (R^2 = R*R) 
  

------------------------------------------------------------------------ 

Case 2: Helical Primary: 

                |<- R ->| 
            --  o       |       o 
            |   o       |       o 
                o       |       o 
            L   o       |       o  N Turns 
                o       |       o 
            |   o       |       o 
            --  o       |       o 

      L = R^2*N^2/(9*R+10*L)  (Vertical Helix) 

------------------------------------------------------------------------ 

Case 3: Inverse Conical Primary: 

  
                                    / \ 
    --  o                          /    o 
     |   o                        /    o 
     |    o   N turns            /    o 
           o                 Z  /    o 
     h      o                  /    o   / 
             o                /    o   / 
     |        o              /    o   /  Angle = X 
     |         o              \  o   / 
    --          o               o    ------------ 
                        | 
        |   w   |   R   | 
                        | 
            |<--  W  -->| 
                        ^ 
                 Center | Line 

          Z = Coil Width (hypotenuse length) 
          X = Angle of Cone 
          h = Z*sin(X)  Effective vertical Height 
          w = Z*cos(X)  Effective horizontal Width 
          W = R + w/2   Average horizontal Radius 
  

     L1 = W^2*N^2/(9*W+10*h)  (Vertical Inductance Component) 

     L2 = W^2*N^2/(8*W+11*w)  (Horizontal Inductance Component) 

      L = SQRT[(L1*Sin(X))^2 + (L2*cos(X))^2] 

------------------------------------------------------------------------