i could be wrong but i think the calculator already includes the inner ring https://srrcalculator.blogspot.com/p/calculator.html

i found a calculator for split rings and one with a outer diameter of 66cm and a trace width of 60mm would resonate at 27MHz and needs about 14pF of capacitance on the split of the gap

its called MFSKpic not quite SSTV more like fax