A quick look at the model says that the required loading inductance is approximately 6.8 mH, if the overall antenna height is 30 feet and the top hat radius is 4 feet. I assumed four 1-inch radials and a single #8 skirt wire around the ends. Actual wire size, or the addition of inner wires to the top hat, will not have a large effect on the capacitance. Lyle, K0LR