I think usb only goes 15 feet.
16 responses Add your response
USB requirements are that the cable be only 26 nSec long, electrically. The reason they give is so that the reflections have enough time to die down. That limits the length to around 15'. We have measured some cables that are a bit over the limit, at 15'. Most are very close to it.
Use longer at your own risk.
To Br3098's point, I agree with avoiding "regular" copper wire UBS cables that are more than 3.5m. A longer copper cable would not be within the USB spec and would likely not give you a signal or cause dropouts. But if you use something like the Opticis fiber-optic cable you should be able to go longer than 3.5m meters with no problem. The USB spec requires a limited length wire cable. But Opticis (and other companies that do fiber optic, etc.) have found a way around this with their implementations. Like I said, I have been using a 30m USB cable and a 30m HDMI cable with no problem and no decrease in performance for several years. Wireless is another equally attractive option, but obviously requires a different (maybe easier) implementation and hardware; it depends on how simple you want to go and what best meets your situation.