Original poster: "Gerry Reynolds by way of Terry Fritz <teslalist-at-qwest-dot-net>" <gerryreynolds-at-earthlink-dot-net> I was wondering if there is a standard criteria for deciding when one needs to go to the next size larger coil diameter. Assuming coils are at a 5:1 aspect ratio, is there a maxium something (voltage, or power, etc) for this decision? Gerry R Ft Collins, CO