Original poster: "Dr. Resonance" <resonance-at-jvlnet-dot-com> A 4.5:1 height to dia ratio works well. Working backwards, 3 x 4.5 in = 13.5 inch winding length. Add 1.5 in on bottom and 1 in on top, then total is 16 inches long. Dr. Resonance > > How long should a 3 inch secondary be for 1200 turns? >