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FERRITE BEAD: THE BUMPS FOUND IN THE END OF A COMPUTER CABLE


A ferrite bead is a passive electric component used to suppress high frequency noise in electronic circuits. It is a specific type of electronic choke. Ferrite beads employ the mechanism of high dissipation of high frequency currents in a ferrite to build high frequency noise suppression devices. Ferrite beads may also be called ferrite blocks, ferrite cores, ferrite rings, ferrite EMI filters, ferrite chokes or ferrous beads..continue..


A ferrite bead is simply a hollow bead or cylinder made of ferrite, which is a semi-magnetic substance made from iron oxide (rust) alloyed with other metals. It slips over the cable when the cable is made, or it can be snapped around the cable in two pieces after the cable is made. The bead is encased in plastic -- if you cut the plastic, all that you would find inside is a black metal cylinder..continue..

Ferrites are substances derived from a mix of iron oxide and oxides (or carbonates) with other related materials, such as nickel, magnesium or zinc. These oxides can be used alone or together to obtain ferrite. Ferrites are indispensable in activities that involve magnet induction. From casting machines to lamination sheets to computer hardware, ferrites are used in a number of industries. While ferrites are extremely important in a range of industries, there are some obvious drawbacks to using this material. However, wherever ferrites are unavoidable, their negative qualities have to be offset with neutralizing factors..continue..

  • Ferrite beads are often employed by EMC specialists to solve noise problems.– Beads have a reputation for magically eliminating some EMC problems
  • Ferrite beads are also often used in high frequency analog circuits.– Frequent application is power filtering continue..
Analysis of these mechanisms shows that RF shield current is a major contributor to all of  them, so eliminating or reducing shield current should be the key to eliminating the interference. Experimental work near WGN’s 50 kW AM transmitter confirmed this hypothesis. At WGN, virtually all cases of interference in both microphones and input equipment, many of them quite severe, were either eliminated or greatly reduced when a cable connecting the mic to the input gear was wound around a toroidal ferrite (Fig 1) to form an RF choke that reduces that current..continue..

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