Topband: Fabricated common mode chokes - Sourcing

[Jim Brown]

On 8/30/2011 10:30 AM, ZR wrote:
> Did you open up a Cushcraft balun to discover that method? I believe 
> some other companies do similar and Teflon wire is used so it doesnt 
> char as does THNN. 

There are baluns and there are common mode chokes. I'm talking about 
common mode chokes.  Some so-called "current baluns" are really common 
mode chokes. Some baluns are wired as auto-transformers, so they depend 
on flux coupling through the core to transform the impedance.  More 
important, the core sees ALL of the transmitter's power.  A common mode 
choke sees ONLY the common mode voltage/current, which, if the antenna 
is reasonably well balanced, is a tiny fraction of the transmitter power.

This makes common mode chokes FAR less subject to overheating than a 
balun operating as a transformer.

73, Jim Brown K9YC