When I measure my computers output voltage it is 4,8 volt and that sometimes requires me to turn off "charge while on" in the scanner. I have 4-5 USB chargers and two of them output 5,2 volt and using them I can use any of my cables at any length but with the others that output 5,0 or 4,9 it is much more sensitive what cable that will work. So it will be mostly the USB source voltage that will dictate what cable that can be used.
Scanner takes 0,7A while scanning, if not charging at the same time that would add another 0,5A.
I don't know why Uniden have set such a high voltage level for the USB warning that disables the scanner as all circuits except charging and audio amplifiers run on stabilized 3,3 volt. It is the same mystery when not allowing recording while running the scanner without a battery, when a SDS200 doesn't have a battery and runs on the same type of power adapter but 12v instead of 5v. It just doesn't make any sense.
/Ubbe