Chris Trask wrote:

1. That it is simply a 2:1 transformer with an isolated primary and
secondary?


No. It is a pair of 1:1 transformers on a single core. I can make it
work equally well by making the two transformers on separate cores. I can
also make it with a pair of equal length coaxial cables. Both of these
realisations defeat his claim that it is a 2:1 transformer.

If it were a mains or an audio transformer with four identical windings,
two primaries in parallel and two secondaries in series, most people
wouldn't hesitate to call that a "2:1" (voltage ratio) transformer. You
could also choose to call it "a pair of 1:1 transformers on a single
core" and that would also be valid, though I don't believe that would be
most people's preferred description.

The same output voltages can *also* be obtained by a different method,
by appropriately wiring two completely separate 1:1 transformers, but
that doesn't affect the way we should think about the transformer on a
single core.


But at the same
time, neither of them answer his claim that it is impossible to make a 4:1
current balun on a single core with a pair of 1:1 transformers.

Agreed.



2. That it is not a true transmission line transformer, because your
transmission-line windings are not being fed with opposite polarities
across the *same* end?


This isn't even a gray area. We're making a BALUN, in other words a
transformer that has an UNbalanced port and a BALanced port, and in this
case fully meeting the definition of a current balun. If we were to accept
the above statement, then we would have no choice except to conclude that in
no circumstances could we make a BALUN with transmission line transformers
because in all cases of BALUNs one port is fed unbalanced.

I was talking about TLT's, not baluns. Some baluns are TLT but others
are not.


Making transmission line transformers is not difficult, although Tom is
making it appear as though it's some sort of great mustery. For a length of
transmission line that is sufficiently short with respect to wavelength,
meaning less than an eighth of a wavelength in practice, the following rules
are observed:

1. The voltage across the one conductor is equal to the
voltage of the other conductor, both in magnitude and
in phase.

2. The current in the one conductor is equal in magnitude
but oppostite in phase to the current in the other
conductor.

These basic understandings of transmission line transformers are well
established and understood. Gary Breed brought the concept down to the
essentials in:

Breed, Gary, "Transmission Line Transformer Basics," Applied
Microwave & Wireless, Vol. 10, No. 4, May 1998, p. 60.

It all comes down to a difference between what is known by way of
established theory and practice versus trying to convince people that
everything we know is wrong.


Sorry, but it all seems to come down to the definitions of "current
balun" and "transmission line transformer" that one chooses to adopt.
Rather than referencing those definitions, please can you quote them
here, in full?


--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek