future reference. A piece of colored
tape with the manufacturer and part
number will identify the part exactly
— no guessing. Or, write on the core
with a pencil or permanent marker.
Another good idea for your ferrites is
to not throw them all in a box
unprotected. Remember that ferrites
are brittle — they chip and crack
easily. Once broken, the core is
probably unuseable. Put the core in a
plastic bag or paper envelope for a
little buffer against its fellow cores.
Ferrite —
the EMI Fighter
In the next installment of the
Ham’s Wireless Workbench, I’ll show
how ferrites are applied in the never-ending battle against EMI from, to,
and by electronic gadgets of all sorts.
We’ll also cover a few other tricks
the hams have learned that you can
apply as well! NV
July 2015 65
Fair-Rite
www.fair-rite.com
Ferroxcube (Yageo)
www.yageo.com
Magnetics
www.mag-inc.com
Micrometals
www.micrometals.com
Amidon Company
www.amidoncorp.com
References
Ferrite or Powdered Iron?
Powdered iron cores have a much
lower permeability than ferrite, but can
also handle the higher levels of
magnetic flux at high power without
saturating. Saturating distorts the
applied waveform, creates spurious
harmonics and other unwanted signals,
and can seriously over-stress a
transistor. For transmitting and other
high power applications, powdered-iron
or powdered-permalloy cores are the
usual choice. The free paper, “A Critical
Comparison of Ferrites with Other
Magnetic Materials” ( www.mag-
inc.com/File%20Library/Product%20Liter
ature/Ferrite%20Literature/cg-01.pdf) —
an excellent overview of different
magnetic materials from Magnetics —
is a must-read if you want to know the
details.
