USB Cable Length?

[tony draper]

Read somewhere that for technical reasons (voltage drop?)the maximum length of a USB Cable was 5M,yet came across Ad yesterday for a 10M active USB2 Cable,what exactly does 'Active mean'
:confused:

[Lantern10]

Not to sure about the "Active" bit but I bought a few of these and they work fine.

Try this it's part number XC4120 from Jaycar.

Powered USB Extension Lead 10m

Extend your USB devices far and wide. The cable has a built-in extender that allows you to go further. 10 metre length. Up to two cables can be connected together to obtain a 20 metre length.

Powered USB Extension Lead 10m - Jaycar Electronics (http://www.jaycar.com.au/productView.asp?ID=XC4120&keywords=xc4120&form=KEYWORD)

[mixture]

tony draper,

See the FAQ at the USB industry association website :

USB.org - FAQ: Cables, Connectors, and Networking (http://www.usb.org/about/faq/ans5)


And for those people promoting Active Cables, see the USB Compliance checklist (http://www.usb.org/developers/compliance/check_list/compchkhub080205.pdf). Specifically page 3, section 1.1 which I'm not going to reproduce here out of respect for copyright. So called active cables are a no-no.

[tony draper]

Is USB cable length dependent upon the device being run by same? frinstance I bought a full 1080p HD webcam last week, I mean a ten meter cable on a mouse might be ok but on summat like this webcam must be squirting a lot more data down the wire than a mouse.
:)

[mixture]

Some devices do indeed have a higher power draw requirement. If you own a mac, you may have already discovered this when trying to plug certain items into the keyboard USB ports only to be told the device power draw is too high for those ports and you need to plug it in elsewhere.

USB was not intended to be a long-range connection, the designers never set out to compete with well established mechanisms such as Ethernet and RS-485. I've never used one myself yet, but there are USB Ethernet Hubs on the market which might satisfy those wanting the distance of Ethernet but the connectivity of USB.

[MacBoero]

We used 5m active USB extenders at work. The active part cleans up the distortion to the signal caused by the lover than usual cable. You can daisy chain the too.

We have found though, that USB over Cat5 extenders are ore cost effective, and go MUCH further. We use some that work over 100m of studded cable, but will easily do 40 to 50m.

E.g. CAT5 USB EXTENDER SYSTEM: Amazon.co.uk: Electronics

[mixture]

Daisy chaining cables ? :rolleyes:

Your place of work sounds like a right rats nest of cabling where a bit of structured cabling wouldn't go amiss....

[A A Gruntpuddock]

Don't know about usb but I was running my camcorder off a Firewire cable plus 2no x 3 meter extension cables without any problems.

[Keef]

Some devices will work with longer cables, some won't.

I needed to put a USB dongle a bit higher (to pick up a signal). It worked with a 5m extension cable, but not with two joined tgether.

[bnt]

Voltage drop is only an issue when you're powering a device by USB, really. But a longer cable and joints can also cause difficulties with data transfer at higher rates. You have issues with electromagnetic fields, capacitance, and so on. There's a FAQ on the subject here (http://www.usb.org/about/faq/ans5), which says:
Q2: Why can't I use a cable longer than 3 or 5m?
A2: USB's electrical design doesn't allow it. When USB was designed, a decision was made to handle the propagation of electromagnetic fields on USB data lines in a way that limited the maximum length of a USB cable to something in the range of 4m. This method has a number of advantages and, since USB is intended for a desktop environment, the range limitations were deemed acceptable. If you're familiar with transmission line theory and want more detail on this topic, take a look at the USB signals section of the developers FAQ.

[jimtherev]

As has been mentioned above, depends what you want to do with the signal, dunnit? In a similar vein, the VGA specification suggests that 5m is the maximum, yet I'm running a projector 25m away from the computer*. Very little degradation of picture, except on the occasion when some bright spark decided it would be neater to bundle the cable with the hearing loop. :ugh:

He has been spoken to.

*Just remembered - 'tis a 10m and a 15m cable joined together with an f-f connector: even worse.

[MacBoero]

Daisy chaining cables ?

Your place of work sounds like a right rats nest of cabling where a bit of structured cabling wouldn't go amiss....


It was only once, at an exhibition when we needed the USB connection to get from where the computer was off stand, to the presenters position. The 5m active extenders, chained together (about 4 of them if I remember) worked flawlessly for the week.