Showing posts with label Ferrite. Show all posts
Showing posts with label Ferrite. Show all posts

September 11, 2015

Who invented ferrite?

Who invented magnetic core material known as ferrite?
  • Dr. Takeshi Takei from the Tokyo Institute of Technology, discovered zinc and iron oxides have special magnetic properties.
  • Professors Kato and Takei applied for a patent in Japan in 1930 for their discovery of oxide magnetic core materials which was granted in 1932.
  • Tokyo Denki Kagaku Kogyo (now known as TDK Corporation) was founded in 1935 to commercialize ferrite cores.  TDK is still making ferrite cores today.
  • Philips applied for a patent in The Netherlands in 1941 for ferrite.

Ferrite Bead

Good DX and 73, NJ2X

July 13, 2012

What is a ferrite bead?

Ferrite is a ceramic made from various iron and other ferromagnetic oxides.  A ferrite bead is considered an electric component which effectively acts as an inductor.  Ferrite beads are often used to reflect and absorb RF (which is dissipated as heat).  The frequency range that a ferrite bead absorbs depends on the material it is made from.

"Type 31" and "type 43" ferrite material are both very popular in amateur radio applications such as EMI noise supression and common-mode chokes.  Common-mode chokes are very useful devices that can improve the received noise level by blocking EMI travelling along power and telephone cables within the home.  Common-mode chokes can also help reduce the level of transmited RF travelling in common-mode on the shield of transmission cable and keep it out the home.  Additionally, common-mode chokes can reduce the level transmitted RF travelling into sensitive devices via power cables and cable TV lines.

Fair-Rite publishes an excellent technical paper, "How To Choose Ferrite Components for EMI Supressions".

Be sure to also see our related article, What is the schematic symbol for a ferrite bead? on NJ2X.COM.

NJ2X's built this Anderson Powerpole pigtail with a ferrite bead to supress EMI riding on the 12v DC line

February 11, 2012

What is the schematic symbol for a ferrite bead?

This is a ferrite bead.

through-the-hole ferrite bead
Ferrite Bead - through the hole variety

So what is the schematic symbol for a ferrite bead?

According to the IEEE 315 standard for Graphic Symbols for Electrical and Electronics Diagrams, the ferrite bead schematic symbol is:

IEEE 315 Ferrite Bead Schematic Symbol

Additionally, there are several other ways commonly used to denote a ferrite bead on a schematic:
Ferrite Bead
Ferrite Bead
Ferrite Bead

Ferrite Bead

Good DX and 73,


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