What is that blob at the end of power supply and USB cables for?

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Mik
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What is that blob at the end of power supply and USB cables for?

I could not stand it any longer and opened one up: It has a iron (ferrite??) cylinder inside it, nothing else.

The cylinder is mounted around both the positive and the negative cable.

What is it for?

What would happen without it?

marylandbob
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Re: What is that blob at the end of power supply and USB ...

Those "blobs" of ferrite act to increase the high frequency impedance of the cable they are installed on, and reduce the radio frequency (RF) interference to and from the attached devices. Without them, the device may cause increased levels of interference to radios and televisions that are nearby, and the device might malfunction, if a nearby 2 way radio, or other RF generating device, were energized. (cell phones generate and use RF) It seems that manufacturers cut corners in production, by leaving out internal, on board feedthru capacitors, chokes, and bypass capacitors for RF filtering, and then add the external ferrites to get the devices to pass certification. Not the best way, but I guess it is cheaper.-Bob Curry

Robert M. Curry

Mik
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Re: What is that blob at the end of power supply and USB ...

Thank you!

So if I want to shorten the cable, would I get the same result as before if I just move the ferrite ring to the "new" end of the cable?
Or is it more complex than that, and the ferrite ring needs to be different if the cable length is altered?

This information may be used entirely at your own risk.

There is always a way if there is no other way!

knabo
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Re: What is that blob at the end of power supply and USB ...

It is not more complex than that. You can move your ferrite bead as you want. There are different types of installation, sometimes you see them with the cable looped around a ferrite core, mostly just the cable passing through. You can buy ferrite beads and clamshell types of various sizes for snapping over an existing cable.

What would happen without the bead? Sometimes nothing. Sometimes external interference to radios, tv's or other rf devices. Sometimes random noise on your own device that can have random effects.

When in doubt, a bead does not hurt.

Luther Burrell, Mesa, Arizona, USA
Rides: ZuumCraft from zuumcraft.com
Previous Rides: Blue Vectrix Maxi scooter

marylandbob
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Re: What is that blob at the end of power supply and USB ...

Yes, you could shorten the cable, and re-install the ferrite at the "New" cable end. For best results, keep the ferrite at the same end of the cable as at first supplied! (In some cases, if the ferrite is moved further away from the end, or to the opposite end, interference is more probable.)-Bob

Robert M. Curry

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