[Discuss-gnuradio] USRP2 MIMO system implementation

[Pan, Luyuan]

Hello,
I want to implement a MIMO system using USRP2, I just have USRP2s and
MIMO cable.
1. Do I have to use an external clock source ?
2. I searched the maillist and found: Each USRP2 can handle 1 antenna
with most daughterboards, or 2 if you
have your own external RF sections connected to the USRP2 at IF.
Does it mean I should buy "external RF sections" to use 2 antennas on 1
USRP2? Or where can I get them?
3. If I want to build a 2X2 MIMO system,-- 2 USRP2s, 1 MIMO cable, the
"external RF sections" said above, -- Is that enough?

Any suggestion is appreciated. Thank you..

-- 
Best regards,
Luyuan Pan