PDA

View Full Version : PC cable question



Rod J
21-07-2008, 10:27 PM
Probably a silly question, but I've always been curious of why PC cables (some USB, some monitor data cables, etc) have a large round section usually near both ends of the cable? I think there is maybe ferrous metal inside because they seem heavier than the plastic or rubber would be alone. One USB cable I have for my satellite TV box (STB) goes through a similar section near the STB end but it actually loops around and goes through it again. What is the purpose of this? I have a feeling it has something to do with reducing interference (induction?) in the cable? :thanks

jwil1
21-07-2008, 10:42 PM
I think it's a strain relief loop.

I've seen some of those with the cable wound 2-3 times round it. For when it doesn't go through I think it's something to pull on to get the plug out.

But don't take my word for it - I'm only guessing :D

Rod J
21-07-2008, 11:11 PM
I think it's a strain relief loop.

I've seen some of those with the cable wound 2-3 times round it. For when it doesn't go through I think it's something to pull on to get the plug out.

But don't take my word for it - I'm only guessing :D

That was one of my thoughts too, that it may be simply something to grip onto when removing the cable. But I suspect there might be something more to them than that. ;)

Burnzee
22-07-2008, 12:10 AM
Hi

You are correct in your assumption these large round sections at the ends of the cables are for reducing interference. They are effective up to approximately 500 MHz.

The sections do contain a ferrite core. The performance of the ferrite core on suppressing the electromagnetic interference is mainly dependent upon its material property, inner diameter, outer diameter, length etc. On the other hand, for a noise with a frequency larger than 500 MHz, the ferrite core may fail to suppress the electromagnetic interference.

Do not use these ferrite cores for removing the plugs. They are NOT Strain Reliefs!!

BURNZEE

bevy121
22-07-2008, 12:11 AM
The cylinder shaped bits are "ferrite cores".

For reducing RF interference.

At least thats what I think they are


*EDIT*

Snap Burnzee! :)

Rod J
22-07-2008, 01:01 AM
Thanks Burnzee and bevy121, your replies have answered my question satisfactorily :) I thought their purpose might be something to do with interference.