Sweet (and sour) spots...musings
I still have optimism about the square law. I suspect that the sour
spots (inefficiency) at low powers are caused mostly by two factors:
1) When a 24" spark was produced, the 13" toroid was probably
too large. A 10" toroid would probably be better?
2) The secondary has too much relative Cself for the small toroids.
It is possible that: Ctop = 1.5 to 3 times Cself is optimal.
I may re-install the smaller 4" by 23" secondary and retest with the
13" toroid at low power, and also try the 10" toroid, and see if the
efficiency increases at the lower input power levels. Relative gap
losses are probably increasing at the low power levels too. I'm
not sure how much effect that might be having.