Dont know how useful this would be but it might be worthwhile measuring
the RF power on the input and output side of the balun in the back to
back exercise. That will give you an idea of loss and as you increase
power, saturation.

Cheers Bob VK2YQA



Build 2 of the baluns and connect them back to back and put a 50 ohm dummy
load on the second one, assuming you are going from 50 ohms to the 450 or
500 ohm impedance unbalanced. Then measuer the swr.