Is anyone using diversity receive to overcome fading issues? Large microwave systems have been doing this for ages.
I envision two antennas coupled together and connected to the A port on the Atheros card, and one antenna on the B port. (Where RX=A TX=B)
How would the Atheros chipset handle input from two different antennas on the same port?
(Next question - When will we have MIMO!?!)
Probably when the 802.11n standard is ratified. 
This is the only miniPCI mimo card I have seen so far.
SparkLAN WPIR-120G Wireless Mini PCI Module
Only 13 to 15db but it would be great to test 3 12db omni’s with.
I am thinking of buying two of these cards. Puting them in 2 WinXP boxs with the 3 12db antennas on each. Put one on the tower and go to the arias that I can’t get a good signal to see if it realy helps.
If it does I will be scraching my head over what to do next. No OS to run it on but Winblows. 