[Elecraft] Balun for KAT2

[Charles Greene]

At 08:22 PM 1/12/2002 -0500, Jonathan Taylor, K1RFD wrote:
>I just set up an 80m dipole with ladder line (600 ohm), and may soon become
>a believer in the open-wire feed.
>
>When using it with an ATU such as the KAT2, with low power, what is the most
>efficient way to convert the KAT2 unbalanced output to the balanced line?
>
>My first inclination is to build a small toroidal balun inside a box and run
>a short length of coax to the rig.  But I have also read that this type of
>balun can be lossy when working through an impedance (on the balanced side)
>far from the design impedance.  (Is the coax length critical?)
>
>Has anyone used the so-called "current baluns" offered by RadioWorks?

I have a current balun made by Radio Works, and it works well.  Some of the 
baluns you can make your self from the links on the Elecraft web site don't 
work so well.  I have built some that work as well as the Radio Works ones, 
but for low power.  Try 13 turns #24 magnetic wire biflar wound on a 
FT114-43 core, then use two cores.  Hookup per Tom Hammond's web site: 
http://home.earthlink.net/~n0ss/download.html  The two core current baluns 
work better than the single core ones.  I have found the current baluns 
work well if you trim your open wire line until you don't have a current 
node on any band in use where the balun goes.  If you use any kind of a 
balun at a current node (high voltage point), it may destroy the balun, and 
if it doesn't actually destroy the balun, it won't work well and will have 
high losses.

You can also use a 1:1 balun, made by placing ferrite beads on the 
transmission line, or by winding some coax in a coil.  See ARRL 
handbook  for the design.  Check QST ads for a 1:1 balun bead kit.


73, Chas, W1CG