[Elecraft] Balun for KAT2

[Charles Greene]

At 11:20 AM 1/13/2002 -0800, Ron D' Eau Claire wrote:

Ron and All.

I'd just like to emphasize a couple points Ron made.  There are two aspects 
of losses.  One is how it affects your antenna system.  The losses of a 
typical balun operated into a SWR of 5:1 or less are insignificant compared 
to the other losses in your antenna system, so don't worry about 
that.  However, a loss of 3% if you are running a KW is 30 watts, enough to 
burn up all but the larger baluns.  I guess the moral is to use a balun 
rated for the power you are going to use, and don't operate it at a current 
node (high voltage point) in an open wire feed line.


>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
>
>
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73, Chas, W1CG