I am intending to build a two element fan dipole for 80 and 20m. How should I go about choosing a ferrite toroid and number of windings for the balun, to operate effectively over such a range of frequencies?
I'm planning on constructing a 1:1 Guanella current balun with bifilar windings, and using 12 AWG landscape lighting wire for the arms at no more than 100W.