This starts with the devices using the voltage on the USB port to operate. The support of that pin as a "hard" 5v voltage source varies all over the map. And it is altogether TOO tempting for a gizmo maker to count on more current than is really available, making USB devices running on 3.5 or 4 volts all too common.
The worst of these power dupes are passive USB hubs. The worst USB ports are laptops and cheep-cheep port cards which were never engineered by anybody, where the 5 volts is via tiny circuit board traces that quickly start to become resistive with any load at all on the USB port. Some of these port cards have *passive* USB Hubs on them, even though there is 5v available on the card pins to reconstitute the supply voltage. Just another reason that the *U*niversal in USB is a joke. 73, Guy. On Mon, Dec 6, 2010 at 6:55 AM, Jim Miller <[email protected]> wrote: > I discovered my new Dell Win7 laptop wouldn't load the K3 unless it had the > external power supply hooked up. It wouldn't work on battery alone. > > I use the lateest FTDI based KUSB. > > 73 > > Jim ab3cv > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
