Hello everyone! Can anyone point out where some 3" - 4" ferrite toroid or cylinders can be obtained from? My current setup includes only some small forms from radio shack. When powering the system up and down I can watch an arc between the form and wires on all the coils. If anyone has the formulas for calculating the inductance on a toriod and/or ferrite cylinder that also would be apprecited. Many thanks in advance! Keith