Reg Edwards wrote:
If it was a fixed 1-to-1 transformer and one end was terminated with
Zx, then the input impedance at the other end would also be fixed at
Zx. But it isn't!

It is for cases where Zx = Z0. The impedance seen looking
into my no-tuner feedline system is between 32+j0 ohms and
80+j0 ohms on all HF bands. On a couple of HF bands the
measured SWR is 1:1 and of course, under those conditions,
the impedance at both ends of the 1:1 balun/choke is fixed
at Zx = Z0 = 50 ohms.
--
73, Cecil http://www.qsl.net/w5dxp

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On Thu, 28 Apr 2005 18:03:40 +0000 (UTC), our tipsy English cousin,
"Reg Edwards" wrote:

Balanced to Unbalanced WHAT ?

"Balun" is a contraction of "Balanced to Unbalanced "TRANSFORMER".

No, I stand by my definition: BALUN is a contraction of BALanced to
UNbalanced.

If you want to call it an impedance transformer, then call it a "BALUN
impedance transformer." The functions are independent. In fact, many
"broadband transformers" separate the functions into "balun" and
"transformer."

For example in Fig 2 of this reference:

http://www.minicircuits.com/appnote/howxfmerwork.pdf


What is the transformation ratio of the W2DU "balun" and other devices
which serve a similar purpose?

Let the complex line constant of the line comprising the balun be x =
alpha +j Beta .

Then with Zl being the load, the input Zin will be found from:

Zin = Zo * ((Zl + Zo *tanh(x))/(Zo + Zl *tanh(x))

Which of course for a lossless line of Zo and a load of Zl = Zo
reduces to Zin = Zl = 1:1

But you know all of this.

Between which pair of impedances does it match?

It isn't designed to "match" anything. It's designed to suppress
common-mode current. Other than that, it's a length of transmission
line that behaves just like any other transmission line of the same
length, loss and impedance. But you know this too.


If YOU cannot provide answers then there are many old-wives who can.

There is a program named BALCHOKE available free from my website.

I have no wish to participate in futile arguments about the meaning of
words. They can drive one to drink

I believe you have arrived.

Then if I hook up a power transformer off 125V, and the secondary is in a
circuit where there is NO return path to ground (and it is suppling a
push-pull circuit), I must stipulate that it is a "60Hz BALUN????"

Give me a break!!!

Regards,
John

"John Smith" wrote in message
...
You are thinking power xfrmr, where an isolation xfrmr is isolating from
ground loops, or possibly even dc.
A 1:1 unun is isolating from rf, the "choke" is implied!


we-yell ah reckon the only time I ever heard of - or seen one of dem-there
isolation transformers was in the context of power xfmrs. They were usually
shielded as well. The applications were usually 'computer-rooms'.

Wonder if we could use a 240 primary to 120v secondary as a 4-to-1 balun ?

It would be (and was often used to go from unbalanced to balanced,
or vice versa) , if the transformer was say , wound one to one , with
the primary, or secondary center tapped, the center tap connected to
one leg (perferably the "ground" side) of the other side of the
transformer. Could accomplish the same with a 110 volt to 220 volt,
center tapped xfmr, again tyeing the center tap to one side of the
primary (but for connection to your ac outlet, NOT the safest
construction proceedure! This was the tecknique used from 75 ohms
unbalanced to 600 ohm ballanced (tho obviously, the winding ratio
was different)! Jim NN7K



John Smith wrote:
Then if I hook up a power transformer off 125V, and the secondary is in a
circuit where there is NO return path to ground (and it is suppling a
push-pull circuit), I must stipulate that it is a "60Hz BALUN????"

Give me a break!!!

Regards,
John

Hey, you could, but "220v-110v HF power transformers" are rare... unless you
buy "Baluns", or, "RF Auto-Transformers" (I made up that name grin) then
they are plentiful!!!!

Regards,
John