Wi-Fi Antennae reception and related connection issues?

Hello,

I've recently purchased a gaming PC (Nightblade B85C), which came with its built-in Wi-Fi receiver and two antennae to attach to it. Despite the fact that I've got a 20 mbit connection installed in the house, (1) the connection barely picks up and (2) it appears to work at a 3 mbit download capacity when I speed test it.

I connect to the same connection via an iPad 2, which seems to work but I cannot receive anything from the same router with a double-antennae. The router is located downstairs, exactly below the computer.

I haven't used a PC for 15 years so I'm pretty ignorant about even the basics. Does it have to do with the position? Or is there an update that would smooth thing up? Or is it a firewall setting that grinds it down to a slow pace? I wouldn"t know any better in any case. As things stand, plugging an Ethernet cable seems to be the surest way but still, it's pretty useless to have wireless connection now.

What would be the sensible thing to do apart from rebooting the router as Windows troubleshooting suggests?

* The machine runs on Windows 8.1

Read more: Wi-Fi Antennae reception and related connection issues?