Hi, I'm building a Yagi antenna for the 440Mhz ham band. The outline I'm following uses a driven element of a folded dipole; Z = around 288 ohms. I am feeding this with 50 ohm source. Many internet sources describe a balun made from a 1/2 wave length coax (velocity factor adjusted). I will reference here http://www.ece.mcmaster.ca/faculty/nikolova/antenna_dload/labs/Exercise1-5.pdf page 1-77 where the balun is described. Now I follow that the voltage is doubled as we extend the transmission line 180 degrees down the line. But I'm really confused about the current paths of this. It seems that the I of the center conductor is all that is used to supply the antenna (load); and further as the coax shields are all tied together and not connected to the antenna at all - where is the coupling for the current that travels back to the transmitter on the shield of the coax? I had fields 30+ years ago, and antennas still mystify me, but I'm not seeing this. Can someone explain this?