Current Balun

[W4AMV]

Decided a current balun for the 20 meter Bobtail or even a dipole is desired. And for some reason got trapped into the voltage balun vs. current balun detour. In any case, had real issues in validating the proper response for the voltage balun as discussed by W7EL. Not sure how well these 1:1 Ruthroff voltage baluns work for folks, however, the responses I measured
on the unit I built as well as the commercial one is less than desired. See photo response of the return loss. In the 20 meter band less than 2:1 SWR but the bandwidth is certainly compromised and of course the ability to provide current balance is questionable. The current balun is best built with coax... Don't waste your time as I did trying to build it from twisted bifilar
wires or tightly coupled wire. The results are average-to-poor. The final current balun done with 50 ohm coax on -61 material shows better than 20 dB return loss from 1 MHz- to well past 80 MHz and the current balance is excellent per W7EL's experiments.

[W4AMV]

And the current balun response:
Thanks, Alan