The following diagrams and tables show some simple 1:1 and 4:1 baluns for use between 1.8 and 30 MHz using twin transmission lines made from enamelled copper wire (ecw). The bifilar windings have been adjusted (spacing) to produce transmission lines with Zo of 50 or 75 ohms as required for best matching. These designs should
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