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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]
------------------------------------------------------------------------