[Elecraft] KAT100 with Ladder Line

[Don Wilhelm]

Curt,

There seems to be a misconception among hams that when using 450 ladder 
line, a 4:1 balun is the best thing to use.  While that may be true in 
some cases, in many other cases, a 1:1 balun will serve better.  It all 
depends on the feedpoint impedance of the feedline at the shack end, and 
that has little relationship with the fact that 450 ohm line is being 
used - i.e. the  feedpoint impedance is *not* the characteristic 
impedance of the transmission line in most cases.  The feedpoint 
impedance looking into the shack end of a multiband antenna can vary 
from extremely low to extremely high - it all depends on the length of 
the antenna and the length of the feedline.

That being said, I would suggest that you use an Elecraft BL2 right at 
the output of the KAT100.  Try it at the 1:1 setting first, and then try 
the 4:1 setting to see which produces the better results for each band.  
It would be informative to measure the impedance into the unbalanced end 
of the balun with an antenna analyzer on each band - use the setting 
that does not produce an extremely low of extremely high SWR on the 
analyzer.  Often adding or subtracting a length of feedline will bring 
the feedpoint impedance into a better range for matching.

73,
Don W3FPR

Curt Milton wrote:
> I admit I enjoyed using a KAT100 at FD, but I wonder
> how much value it would be at my station.  
>
> For feeding my wire antenna with balanced line, I
> suspect I need an external balun, that has to go
> someplace, and better to be attached to one of the
> tuner inputs.  Currently I use a manual MFJ tuner
> (with its internal 4:1 balun) to operate my wire
> antenna on 30, 40, 80 and 160m.  I can imagine the
> autotuner being useful here, but I can't envision the
> balun to use and how to attach it to the KAT100.  
>
> My other antennas are 2 multiband verticals (80/40 and
> 20/17/15/12/10), and these are nicely matched where I
> operate - so not much utility for the KAT100 here.  
>
> So will a KAT100 make my QSY more seamless, and what
> balun to use and how to integrate it ?
>
>