QualComm Atheros doesn’t provide a download for the AR9485 WiFi Driver for Windows 8.1 on their website. If you need the QualComm Atheros AR9485 Driver for Windows 8.1, you can download it from this link:
Personally, I would avoid downloading the driver from an unofficial publisher or website that isn’t a trusted partner of QualComm Atheros, because it may be a trick to get you to install a virus or the real driver may be bundled with a virus.
There is a more recent driver for the QualComm Atheros AR9485, but this should come with Windows 8.1 or get picked up when you right click the driver in Windows Device Manager and go Update Driver. At the moment, I’m just testing the old driver because after a recent Windows 8.1 update I’m having intermitant issues that I suspect may be related to the QualComm Atheros AR9485 driver.