Communication issue between SBX and XCVR2450

Hi all,

I have two USRP N-200 boards, one with SBX daughterboard, and the other
one
with XCVR2450 daughterboard. They use the same VERT2450 antennas. I
tried
to transmit from SBX to XCVR2450 using benchmark_tx.py and
benchmark_rx.py
in ofdm folder. But nothing was received at the receiver side. I also
tried
another direction, using XCVR2450 as a transmitter and SBX as a
receiver,
and nothing was received, either. However, two USRPs with two XCVR2450
daughterboards or two USRPs with two SBX daughterboards can communicate
successfully. What prevents communication from happening between SBX and
XCVR2450? Is that because of the LO offset? But two USRPs with XCVR 2450
also have LO offset, why they can communicate successfully?

Thanks in advance.