Original poster: "raven0075 by way of Terry Fritz <twftesla-at-uswest-dot-net>" <raven0075-at-home-dot-com> I am looking about 13 turns 1/4 copper tub, how much space do I want to leave in-between the coils, with a 4.5 Diameter primary. at 900 wraps 24awg wire. thanks