Use external WiFi adapter instead of internal
You need a proper driver to run your external Wi-Fi adapter.

Check this page, choose Product Category -> Indoor Wireless, Product Model -> AWUS036NH, Type of file -> driver and solve a captcha to get to the download page.

Download the driver for Mac OS X 10.9 and try to install it. If this driver doesn't work with Yosemite you probably have to contact the support there.