I've just acquired a
USB F5D8053ed Belkin adapter and it is unreasonably slow.
Details of how I installed the firmware and device driver are described in this AU Question.
I believe there is either a problem with a driver or adapter itself that is preventing from using the full network quality. At the moment I can see that my Windows laptop is performing at 30 x speed better than the Ubuntu desktop PC with Belkin.
What are they ways to troubleshoot pure wireless network performance on Ubuntu?