What and why is this node in a USB 2.0 cable?

Hello,

I am about to buy a USB extension cable and i came across this listing which shows a USB cable with a node and then there are other listings without the node. I can't find any information about this node. What is its purpose and should i get a node USB cable for better performance??

usbnode.png

usbnode.png

If you are talking about the ferrite choke, read this:

Thanks a bunch! I was wondering why it's there and now i will go order a cable with a ferrite bead/choke. :slight_smile:

In practice, it makes very little difference if any.

Paul__B:
In practice, it makes very little difference if any.

yes, i was wondering about that - since it’s only at one particular section of the cable, and there’s a whole length still that could “disturb and interfere”.

and yet so many cables have that choke - is it just for marketing purposes - as an “added feature” ?

The choke is at the equipment side where it supposably absorbs any RF generated within the equipment.

You usually see that choke on equipment that must pass FCC certification. Like maybe on the cable that comes in the box with a camera.

It works both ways: it stops interference getting into your device from the cable and it stops the cable from radiating interference produced by the device.

MorganS:
You usually see that choke on equipment that must pass FCC certification. Like maybe on the cable that comes in the box with a camera.

That is indeed the reason.

MorganS:
It works both ways: it stops interference getting into your device from the cable and it stops the cable from radiating interference produced by the device.

It may. But in fact, its effect as a “single turn” inductor is limited to VHF and above frequencies - 30 MHz at the very least. FM radio and TV interference. There is very little in the average household or business that will generate such frequencies, and your Arduino at least would not be particularly sensitive to frequencies well above its clock.

Paul__B:
There is very little in the average household or business that will generate such frequencies

Every computer and digital circuit generates them, this is why commercial electronics has to pass certification.
For USB the Ferrite choke is designed to reduce broadband emissions from the cable emanating from the computer or hub. Ferrites are complex, there are hundreds of formulations all with different response curves.

Ferrite beads and chokes like this are typically engineered to be resistive at the frequencies of interest to absorb energy rather than bounce it around.

My point was that very little in the average household or business will generate such frequencies in anywhere approaching sufficient strength to interfere with the operation of an Arduino - or USB device in general - so it is more about outgoing interference than incoming.

larryd:
The choke is at the equipment side where it supposedly absorbs any RF generated within the equipment.

As pictured.

usbnode.png

Video cables commonly have two. :grinning: