[TowerTalk] Baluns! Ack!
jim at audiosystemsgroup.com
Wed Nov 9 08:22:13 EST 2005
On Tue, 08 Nov 2005 11:07:13 -0900, Justin Burket wrote:
>My question is; with such a high permeability can I make any use of
>these for a balun? I'm constantly coming across a need for one and I
>would love to make use of these toroids instead of having them sitting
>around in my desk drawer.
Permeability for a ferrite is not a single number, it varies with
frequency. AND, it is a complex number -- that is, there is a real part
that describes the inductive component of its series equivalent circuit,
and there is an imaginary part that defines the resistive (loss) component
of the series equivalent circuit. To know whether (or how well) these
things will work as a balun, you need to know what those values are at the
The fact that these parts came from a DC-DC converter suggests that they
are a material that has low loss at LOW frequencies, but not at the higher
frequencies where you will be transmitting. Loss will cause them to
overheat when you transmit. One toroidal cores that makes a good
transmitting balun is made from a ferrite material like Fair-Rite #61, that
has very low loss in most of the HF spectrum.
>I have to admit I'm a bit confused about the theory of baluns and
>searching around the net left me even more confused..
The ARRL website has many good references. If you are a member, you can
access them at no charge. There are also two applications notes in the
publications section of my website. They don't address baluns, but they do
Jim Brown K9YC
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