Step-By-Step Construction of a 4:1 Current-Type Balun
Article by Charles Greene, W1CG My 4:1 current-type balun is wound on a FT-114-43 core. The FT-140-43 is a little easier to work with, and maybe the FT-140-77 would cover 160-10. This one is reasonably flat from 4.5 to 35 MHz but drops off a little at 3.5, 40-ohms with a 200 ohm resistor on