View Full Version : USB 2 Maximum Cable Length

04-14-07, 08:25 AM
My backup device is a USB 2.0 250 MB Iomega Hard Drive.I'd like to put
it in my garage, requiring about 20 to 25 feet of wire. The official
USB specs say 5 meters max; if further use a hub/repeater.

I'm wondering how realistic the 5 meter spec is. I recall that parallel
printer cables were supposed to be limited to 10 feet or so; 75 foot
cables worked just fine. Same thing with the specs for RS-232 cables.

Does anyone have any real world experience with long USB 2.0 cables?
I'm thinking of building mine using unshielded CAT5 cable, one twisted
pair for power, another for data. Wise? foolish?

04-14-07, 02:01 PM
I've pondered about this too.. I have a a computer, sitting outside this room, thats roughly 10 feet away from my desk. When you realistically route them, its closer to 15 feet, plus the extra length of the actual device cords to add.

For USB, I decided to just go with a repeater cable, and then a powered hub, so I didn't have to worry about signal degradation. (x2, so 2 usb ports from my computer branches out to 8 ports total) The USB hub also gave me a more ports, but more importantly, made sure the power levels were high enough , since I also have a Axiom Keyboard Controller(for music) thats driven off USB power. If I can do it over agian, I'd probably just use a plain USB 5 meter cable, connected to the powered hub at the end.

IMO, I wouldn't risk it, especially for actual data transfer to a HD.. If I was in your case, I'd consider using a 5 meter cable from your computer to a powered hub, then another 5 meter cable from the powered hub to your drive. (assume your HD runs off USB power)

I read around and seen mixed success with people just using a long cable.. But if I remember, all of them had issues with power drops at the end of the cable. Which makes me wonder how much the data signal is attenuated then.

However, if you want to test it out with cat5, I'd at least keep an eye on the power levels thats seen at the end of the cord, to make sure it didn't drop too much over the cord, cause I assume this HD runs off the USB power.

The DVI spec also calls for 5 meter max I believe too... I did more research on that, and it appears people have driven it further than that with no problem.. I have a 20+ foot DVI cable and it works perfectly... and thats much higher in data rates than USB.. This cable is pretty thick and shielded though.. and cost $70!

04-14-07, 08:49 PM
Have you seen the price of fibre optic cables!! , I nearly messed myself when I saw them.