[Prev][Next][Index][Thread]
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