[TenTec] 160 meters, ten ted 238 tuner, part two

Jim Brown k9yc at audiosystemsgroup.com
Thu Oct 31 21:42:32 EDT 2013

On 10/31/2013 2:39 PM, Rick - DJ0IP / NJ0IP wrote:
> A BALUN and an RF Choke are synonymous.  They are the exact same thing
> (except for the connection terminals).


I know of nearly a dozen VERY different things that are described by the 
word "balun."

An RF choke is an inductor, and it some frequency it will resonate with 
its own stray C.

A coil of coax is an inductive common mode choke -- the fact that it is 
inductive makes it a LOUSY common mode choke. It is often called a balun.

A coil of coax wound through lossy ferrite cores is a RESISTIVE common 
mode choke -- resistive because the ferrite core is lossy, because it 
resonates with its own stray C, and the choke has been wound to place 
the resonance  in the range of frequencies where we need a choke.

A bunch of ferrite beads on a piece of coax is a common mode choke. Most 
such "string of beads" chokes are inductive, which makes them lousy 
common mode chokes. The original W2DU common mode choke that he called a 
current balun used 100 or more  #73 ferrite beads, which are made only 
in a size that fits small diameter coax (RG58), and which DO  have the 
desired low Q (very lossy) resonance in the HF bands. These original 
W2DU chokes are GOOD common mode chokes.

A half wave of coax has used as part of the  feed of monoband antennas, 
and that is called a balun.

There are arrays of common mode chokes (series/parallel) that used to 
transform impedance and are called baluns.

There are multi-turn transformers that are called baluns.

There are active electronic products that drive video onto CAT5 cable 
that are called baluns.

All of these are VERY different from each other. None of them are an RF 

73, Jim K9YC

More information about the TenTec mailing list