Anyone have any experience of these such as: http://cgi.ebay.co.uk/NextG-USB-TurboTenna-WiFi-Booster-Antenna-for-DELL-IBM_W0QQitemZ170438279760QQcmdZViewItemQQptZUK_Computing_Networking_SM?hash=item27aee9c250 mate wants to pick up a hotspot about 250 m away. Cheers