What is the difference between a voltage balun and a current balun?
This question just came up on the Hawaii Afternoon Net (which meets at 7.088 MHz, or 3.888 MHz when band conditions require it, at 0200 UTC (4PM HST) every day). The answer I gave was a quick one, but does answer the question.
A voltage balun is basically a transformer. You use it to transform the input impedance to some other value. 50 ohms to 300 ohms or 75 ohms to 600 ohm, or something like that.
A current balun is basically a choke. You would use it to present a very high impedance to an RF signal traveling along the OUTSIDE of the braid in your coaxial cable feed line. This forces equal currents in both sides of your balanced antenna, and would reduce the amount of “RF in the shack” by reducing common mode current along the feed line.