Cec, a choke balun has an indeterminate ratio.

A choke balun which the man asked about, is, as you say, a current
balun.

I don't doubt that there are some forms of current baluns which have a
definite ratio. But they have more than two wires. They can be used to
transform one admittance or susceptance to another. ;o)

One thing for sure - they are all transmission line transformers -
for the want of a better name!

In some ways they are remarkable components. They should have been
invented 100 years before alongside ordinary L,C, R & G. But they had
to wait for the invention of ferrites which I understand did not occur
until the early 1940's in wartime Holland. But I would not be
surprised if somebody comes along with the idea that the invention was
in Bell Labs in the 1930's. Even before the Smith Chart which was an
adaption of similar charts in use in the late Victorian Age.

In the 1950's I met an American engineer who told me that in 1945
there were Americans looking round bombed-out German radio factories
and by chance came across some tiny top hats with narrow brims and
with 3 fine wires sticking out of one end. "What on Earth are these"
they asked.

I could go on. It's the Devil which makes me say such things. ;o)
----
Reg.