Ian:

Yes, you inject a VERY GOOD point here--I realize my "definitions" are a
bit blurry. And, indeed, scanning the internet suggests there are some
others out there suffering the same.

What can we all agree are proper definitions to balun, "rf transformer",
etc... I admit I have not ever set up a solid foundation of knowledge
here--just used ideas, plans, etc which others have made available...
and referred to them by the names given... this leaves me at a loss
while I investigate.

John

"Ian White GM3SEK" wrote in message
...
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