[TenTec] 4229 Tuner Balun Replacement?

[Jim Brown]

You have hit on the heart of the reason why I am so opposed to the use 
of the word "balun" to describe a half dozen different things that are 
very different from each other, and why I use the words "common mode 
choke" when I mean a common mode choke. :)   In this respect, it's 
exactly like the word "ground" (or "earth" in British English).  The 
word "ground" is used to describe a half dozen different things 
(connections to the soil, connections between equipment for safety, 
circuit common, termination of cable shields, etc.), and that leads to 
MASSIVE misunderstandings about anything related to the uses of the word.

This mis-use of words leads to a LOT of confusion about what things are 
and how they work.   The most generic definition I've seen of the word 
balun is that it is some sort of device that allows connection of a 
balanced circuit to an unbalanced circuit.  Some use the word to include 
the matching of impedances.

An ordinary transformer allows the connection of balanced and unbalanced 
circuits to each other, and, depending on the turns ratio, can also do 
some impedance transformation.

Transmission line transformers of various sorts are also called baluns, 
and many of those variations are VERY different from each other.  Some 
use transformer action with windings coupled via a ferrite core, while 
others use windings configured so that the core sees only common mode 
current. Some use cores that are predominantly inductive with very low 
loss,  while others use cores that cause the choke to function 
essentially as a low Q parallel resonant circuit.  The design, 
effectiveness, losses, dissipation, and voltage stresses, are very 
different from one type of so- called "balun" to another.

Another completely different so-called balun is a half wave length of 
transmission line that allows the two sides of  a tee-matched driven 
element to be driven by coax. The coax feedline connects directly to one 
side of an antenna and the center of the driven element, the half wave 
of line connects from that point to the other side of the antenna and 
the driven element so that, at resonance, the opposing sides of the 
element are driven 180 degrees out of phase so that their total fields add.

If you live in the video world, you can buy a piece of electronics that 
allows the 75 ohm video output stage to drive unshielded twisted pair 
(like CAT5).  That box is also called a balun by those who sell and use it.

73, Jim K9YC

On 11/14/2010 5:49 PM, Richards wrote:
> Apropos our previous discussion of "choke baluns"...
>
> I believe the locution "choke balun" is often used to refer to various 
> forms of chokes - sometimes made of ferrite beads and sometimes made 
> of round ferrite toroids.  I presume you are talking about the more 
> traditional and more robust "balun" (transformer) designs which employ 
> large, round ferrite toroids - and not the so called  "choke baluns" 
> comprised of a series of ferrite beads along a stretch of coax.