A current balun (as described by W2DU in his book ''Reflexions''), put at
the center of a dipole, prevents HF current from flowing in the outer shield
of the coax. This is due to the high impedance caused by the ferrite rings.
Now, if instead, I put a voltage balun, what should prevent the current from
flowing in the outer shield of the coax? Am I missing something?

Thanks for helping.

Chris