The installation under Windows 7 is simple: just download the driver from the manufacturer's website and follow the instructions: any changes to network settings are necessary.
The improvement in my usual conditions of use is compelling: I spend a reception 0-2 occasional bar, a stable reception at 3 bars, sometimes 4, which allows me to surf without disconnections :-)
The device is completely 'transparent': when I am in good conditions of reception, I disconnected and wifi reception is normally done through the integrated antenna to the PC: no need to go through the configuration when connecting or disconnecting box the antenna is very significant.
The price of twenty euros seems normal for this type of product, and for the services rendered.
Warning: this is not a wifi signal amplifier: it will only work for the computer on which the antenna is connected via USB.
I give 4 stars and not 5, because on this type of device it is unfortunate that no clip or fixing is provided for attaching it to the computer.
Erwann on Amazon.com
