[Elecraft] Balun for KAT2

[Ron D' Eau Claire]

After I posted the message about using a couple of small light bulbs for
checking the 'balance' at the output of a balun, Chas, W1CG, dropped me a
note that said:

"I have made some and run some efficiency
tests.  The 13 T on a FT114-43 core is 97% efficient into a balanced 200
ohm load, and is 90% efficient into a 5:1 SWR.  They are small and use high
permeability ferrite to get enough inductance to operate at 1.8 mHz with a
5:1 SWR, (110 uhy).  A lower loss ferrite or powered iron core would have
lower losses.  The loss of 3% is 0.13 dB, and the loss of 10% is .45 dB.  I
use one on a my W3EDP antenna which runs 5:1 SWR on some bands, at 100
watts.  The loss of a 1:1 using beads or a coax coil is less lossy."

Charles has written about that before, and I hope he doesn't mind my
repeating it here because it is good stuff.

Just because a balun CAN be inefficient doesn't mean that it IS inefficient.
I have successfully used them in many conditions. My warning was only that
they CAN be power eaters and that it is not always as obvious that's what's
happening. One time I did get a warning when I smelled a funny odor running
10 watts on 40 meters. It was the plastic on a banana plug connector to my
feedline melting from the high r-f voltage at that point! The balun - one
out of a "300 watt" MFJ tuner - was also hot.

Since then I've found that, most often, the balance to the feeders goes to
pot when the balun is pushed too hard. That's why I suggested the little
light bulb test as one way to get a clue about what is happening.

But, as Chas has documented from his tests, you can expect a decent balun to
behave very well much (perhaps most) of the time as well.

Ron AC7AC
K2 # 1289