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Re: Top Toroid



Another timely note from Richard in replying to this......

> >    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.
> >
> >
> >
> 
> Bert,
> 
> I trust these are calculated values!!!  I can almost tell due to the fact
> they are all in error from real world, honest to God, measured values.  A
> true, relative isolated toroid is usually about 25-30% lower in capacity
> than the calcs say it is.  My 12X3 spun unit is 7.8pf and my 5X20 is 15.1
> pf.  put them on a coil and they can appear to be even more than calculated!
> It's a crap shoot!  The thrust is that the math isn't even close for  any
> form of critical engineering purposes. Especially on small toroids.
> 
> 
> Richard Hull, TCBOR

I posted on my experience with my one and only toroid late last year.
Measurements 19.5" outer dia. with 4.5" ring diameter. C isolated
calculated to be around 20pF or so (figures above). C when popped 
about 4" or so above a short 9" resonator was about 13 - 14pF. C
when put 3" above my 17" resonator, about 6 - 7 pF!!

Malcolm