[Elecraft] NOT the feedline (was KPA-1500 faulting on 6m; SWR issues)

[Jim Brown]

On 5/31/2020 7:22 PM, Peter Dougherty wrote:
> This is a brand-new balun from InnovAntennas, made specifically for this
> antenna, received this past Thursday.

The word "balun" has been used to describe nearly a dozen VERY different 
physical things, and is thus totally useless as a descriptor of what you 
used (or what they sold you). Buy me a case of a good single malt Scotch 
and I'll run down the list.

I have extensively studied only one set of those "things," common mode 
chokes formed by winding a length of transmission line onto a ferrite 
core that is lossy at the frequency(ies) of interest, forming a parallel 
resonance in the common mode circuit where the RESISTIVE component of 
the low-Q parallel resonance is what makes the choke work.

A good common mode choke does not interact with a well-designed antenna 
unless the Zo of the transmission line wound onto the ferrite core is 
mismatched to the antenna. And I emphatically do NOT call them "baluns" 
because use of that word obscures understanding of HOW they work.

73, Jim K9YC