I get bad reception with my TP-Link PCIe Wifi Card! What can i do?

First try to turn off or move any electrical appliances that are close to your computer (ie microwave over)

If that does not apply in your case, you could get an extension like this.
http://www.buy.com/prod/3m-antenna-rp-sma-extension-cable-wi-fi-wifi-router/q/sellerid/23962916/loc/101/213271820.html

You will then be able to bring the antenna to a better location (without interference) and get better signal.

That given that the Access Point you use is within range

Often times the antennae on these routers come loose. Ensure that the antennae are firmly plugged in.

Try also changing the channel. Routers have 11 to 13 possible channels and most default to 1 6 or 11. Try a different number to reduce interference.

Physical construction of your house can hinder wifi reception. This is often subjective and your best bet would be to move the router around the room or into a different room if possible.