Re: Wire and ferrite baluns

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From: Hugo (hugo@optonline.net)
Date: Sat Sep 28 2002 - 12:10:28 CDT


You can use ferrite to make either a voltage or current balun.

With Iron powder, since the permeability is much less than ferrite, size
does matter and you can not use a small core.
The same turns ration don't apply. The desired bandwidth is easier to
achieve with higher perm cores. Most of the time the price to pay is low
efficiency, (heat loss), although you see a nice match with the network.
Speaking of MFJ, they have a reversible L 'mobile' tuner (don't know the
model, but you might know it), with a coil wound on two stacked ferrite
cores about 1 1/4 " diameter that matches almost anything with a nice
bandwidth. If you thing about it, the reason is simply the horrible losses
in that core that makes it so easy to match to a low VSWR

Also never forget that the core is only necesary for lower bands. The same
"wideband-cure_it_all" balun (80-10M), doesn't make use of the core's
magnetic properties on higher bands.

I don't know who LBJ is nor what he or she sells, therefore I can't tell
whether the design is flawed or you wound it wrongly.

My point is that you can even make an efficient current (choke) or voltage
balun with either or NO core at all.

It seems to be a confusion amongst some list members on this issue. The
ARRL Antenna Handbook has plenty of info about transmission line
transformers.

72,
Hugo
AA1XV a.k.a. CX9AAK


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