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Re: Top Toroid




   Jeff,
    Here is a small list of Toroids and there capacitance in picofarads:

   Toroid (height X diameter)         Picofarads

          3 X 12                        12.95
          5 X 14                        16.08
          5 X 20                        21.58
          7 X 30                        32.17
          6 X 36                        37.18
         12 X 36                        40.84
          8 X 48                        49.58
         12 X 48                        51.79
         12 X 60                        63.32
         20 X 60                        68.07

 
    The Toroid is measured in inches.
    One quick remark. try to construct the cap with the least amount of
metal just a thin shell of metal is best (aluminum duct tape on 4 pvc
joints fitted together works well) The reason being is that the top cap is
also in the midst of the magnetic field that is set up by the primary ind.
If the terminal cap was a solid chunk of metal, the changing magnetic
field would set up an E field in the cap and induce current flow causing
heating of the Terminal cap which is a waste of energy. you don't want the
toroid to soak up the energy of the magnetic field you want that energy to
be soaked up by your secondary coil.
     There is a good toroid home brew description on Bill Beaty's Tesla
web page.     
                       enjoy!
                           --Bert S.