I do not understand how a 9:1 unun wound on a T200-2 works. I understand the transformer voltage and current ratios. I have wound several toroid chokes and 49:1 ununs and know how they work. What is throwing me is that all designs I see use type 2 material powdered iron, for example, a T200-2 core.
The permeability is so low the 9-turns at 2 MHz produce roughly 12-ohms impedance. 30 MHz is not much better at 180 ohms. I was taught the impedance of the windings at a minimum is 10X the circuit impedance or at least 500 ohms, and greater than 500 is better.
It seems to me if one uses type 2 material would take 100 or more turns to get the impedance high enough. Why not use type 43 or 61 material for the core? Impedance will range from 1 to 15K ohms. What am I overlooking?
