Original poster: "resonance" <resonance@xxxxxxxxxxxx>220 to 240 mils is the max recommend range for a nst sparkgap. Beyond that and you will begin to severely strain the nst even with a protective filter circuit. During initial tuning, keep the gap to around 140 to 150 mils max setting.
Dr. Resonance Beware, large gap settings place heavy
loads on NST, and they are rather fragile. Sincerely: Jared Dwarshuis