The entire difference between Chris and I is in my opinion he built
what most of the world would call a transformer. There is no forced TEM
mode excitation that I can see.

Sevik clearly drew a pair of transmission lines, and that was what I
was discussing (and I even exempted a primary/secondary transformer.

If I take a true transmission line choke balun and remove the core,
electrical line length does not change significantly. Chris in an
earlier post claimed the core lengthened the electrical "line length".

Also I'm assuming he didn't use 100 ohm lines, as a TL 4:1 balun
requires. He used coax, which as far as I know isn't easy to make at
100 ohms.

The limited SWR BW, the fact the core affects the electrical length of
the "lines", the high loss (.1dB), the fact the lines don't need to be
100 ohm lines, the lack of differential mode excitaion of the
start.....all point to operation like any other interleaved winding
transformer including audio and some power transformers.

I don't think an isolation transformer is "new art", but calling it a
transmission line transformer might be new! ;-)

73 Tom