Topband: Beverage Feed Line Choke Installation

[Jim Brown]

On Mon, 01 Jun 2009 14:14:53 -0400, Bill Tippett wrote:

> I *believe* the DXE style physically breaks the flow of common 
>mode current through the  shield by using isolated transformer 
>windings through a 1:1 binocular core transformer.

A real transformer certainly does break that current path. BUT -- 
any asymmetry between the windings, as well as any stray 
capacitive coupling between the windings, provides a path between 
windings for common mode current. 

The highest quality audio transformers (for example, www.jensen-
transformers.com) are wound with a foil barrier between windings 
that functions as a Faraday shield when properly wired to external 
circuitry. 

>It would be interesting if someone could define "extremely high 
>isolation impedance".  :-)

I've done my part by publishing graphs of measured data and 
documenting exactly how measurements were made. :)  

BTW -- I object to use of the word "balun" to describe what is 
really a two-winding transformer (for example, in Carlos's 
otherwise excellent description of his RX antenna). Likewise, I 
object to use of the word "balun" to describe what is really a 
common mode choke. Using the wrong word leads to confusion and 
muddy thinking. 

73,

Jim K9YC