I am currently on vacation and my Hotel offers free WiFi in the lobby. The reception on the third floor, where my room is, is pretty bad on my Thinkpad and my phone doesn't receive anything at all.
Fortunately, I am always carrying a high gain USB WiFi stick with me that gave me almost optimal signal strength.
Having 2 network cards ((My Thinkpad's internal card (named "Wi-Fi") and the USB card (named "Wi-Fi 2") )) I was able to use my Windows 8.1 machine as a Wireless Repeater using the following code in a batch file:
That's all.
netsh interface set interface name="Wi-Fi 2" admin=disabled
netsh wlan set hostednetwork mode=allow ssid=%YOUR_NETWORK_NAME% key=%YOUR_NETWORK_PASSWORD%
netsh wlan start hostednetwork
netsh interface set interface name="Wi-Fi 2" admin=enabled
netsh wlan connect name=%HOST_NETWORK_PROFILE% interface="Wi-Fi 2"
%HOST_NETWORK_PROFILE% name by entering netsh wlan show profile in a CMD window.
On first use a new network interface is created. you can see its name on the network adapter page in the control panel: Control Panel\Network and Internet\Network Connections. Mine was named "Local Area Connection* 40". Now you have to share the Internet connection from your second adapter to this interface ((You only have to do this once)) . To do this, right click "Wi-Fi 2", select Properties an go to the Sharing tab. Change the settings like this: 
That's all.