> The Palomar data sheet says #6 is good for 2-30 MHz.
Part of the problem is that what is "good" for use in an energy storage or
transfer device (an inductor or transformer) is not the same as "good" for use
in an RF suppression device. If you are building an impedance transformer, you
want complex permeability that results in very low loss. If you are trying to
soak up common-mode RF, you want complex permeability that results in
dissipating energy. Using a core designed to make good inductors can actually
make RFI problems worse by creating a resonant circuit or by cancelling
capacitive reactance already present. (This is a far more complex subject, so
to speak, than can be discussed in a short email.)
You have to look at the complex permeability of the material to determine the
characteristics of the resulting impedance. Most plots of impedance versus
frequency for ferrite materials (including Fig 27.18 in the new Handbook) only
show impedance magnitude without phase angle. The result is that it's not
clear why #31 material is much better for RF suppression than #43 material at
lower HF frequencies - the magnitudes of the impedance simply aren't that
different. You have to look at the permeabilities, as is covered in the 2010
and 2011 Handbooks in Chapter 5.
We're trying to make this clearer, but it is relatively new information (to
hams) and will take some time to "permeate" the amateur radio world.
73, Ward N0AX
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