I've used this excellent reference  for identifying Ralink 802.11g devices. I would like to find a USB device that supports a, b, and g rates. I see from  that the Ralink RT5201U chipset offers a USB interface and supports all rates. And I see from the driver source code that the 5GHz 11a rates are supported by the driver. But what off-the-shelf device uses the RT5201U chipset?
 http//www.ralinktech.com/ralink/data/R ... ochure.pdf