I gave up using a USB dongle for my desktop (which was operating on the 5Ghz band with an AC enabled router - drop outs, reduced connection speeds were the order of the day. Ended up buying an internal network card with external aerial. The desktop hasn't moved and the aerial is just plonked on it's lid - hidden under the desk. Far superior performance though. No drop outs, etc and have come to the conclusion that USB dongles are best used with a laptop.