Original poster: "resonance" <resonance@xxxxxxxxxxxx> You need to test this dynamically.Everyone does it a bit different, but I use 1 to 2 inches and then check corona spray at night with a 60 sec time exposure and B&W film, ASA 400. Spray from top turn should be slightly below horizontal. If it goes above horizontal you need to lower the toroid. This technique works very well for all coils both solid state and classic. Shoot several exposures at different toroid levels using plastic shims (PVC tube) and look at the resulting pattern.
BTW, did you receive the caps ok? Dr. Resonance
I remember discussing many months ago, the optimum mounting height for a toroidal topload, in relation to the uppermost winding on the secondary, but... ... is the calculation the same or similar for a spherical topload? If not, what is correct for a spherical topload? -- CC