LAB PROOF (1)
According to Steve, G3TXQ:
Because of Sevick's pre-occupation with differential-mode performance he never spotted that effect. In fact he made lots of DM measurements - DM impedance, phase delays etc - but with a *floating* load; and as we all know, if you have a floating load you don't need a balun to maintain current balance :)
The simple fact is that a 4:1 Guanella balun wound as two 1:1 chokes on a common core will force voltage and current *imbalance* with any non-floating load; I don't call that "working" !
For a 4:1 Guanella balun to "work" properly and drive equal currents into any load, the CM voltages of the two chokes must be able to take up different values; they can't do that if they share the same magnetic circuit.