Re: [OT] "Backward" Baluns

Posted by Guy, K2AV on Aug 07, 2010; 9:49am
URL: http://elecraft.85.s1.nabble.com/OT-Backward-Baluns-tp5382873p5383307.html

It depends on what "balun" design you are talking about.  Some 50:200
baluns take a pair of 100 ohm feedlines wound on ferrite toroids to
choke off common mode current, connect them in parallel on the 50 ohm
side, and in series on the 200 ohm side.  This design will not do
50:12.5.  Others will not work well because the 50:200 assumes the
lower current on the 200 side at QRO, and a different design 50:12.5
is specifically wound with QRO high current of 12.5 in mind.

Alas, there is no simple answer to your question, and in every case
depends upon the nasty and subtle details.  "Understanding, Building,
and Using Baluns and Ununs, Theory and Practical Designs for the
Experimenter", by Jerry Sevick, W2FMI (SK), is a good reference that
will get you sufficiently muddy in the details.

73, Guy.

On Fri, Aug 6, 2010 at 10:57 PM, Al Lorona <[hidden email]> wrote:

> A 4:1 balun is always shown and talked about with the low impedance 50 ohm on
> the unbalanced side and 200 ohm on the balanced side.
>
> Can it be connected backwards: 50 ohm unbalanced on the high impedance side, and
> 12.5 ohm balanced on the low impedance side?
>
> Al  W6LX
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