Full Duplex and RFX900 USRP2

Hello,

I have an application that requires me to continuously recieve a signal,
while
continuously transmitting a delayed version of that recieved signal. As
a result
I need full duplex. I have a USRP2 and the rfx900 daughter board. My
plan
is to use the TX/RX port to transmit while using the RX2 port to
recieve. However,
I can not seem to get anything to listen/recieve on port RX2. For
example when
I run usrp2_fft.py and insert

self.subdev.select_rx_antenna('RX2).

this gives the error shown below. By searching this forum I see where
someone
has suggested that I rebuild the firmware by making these changes (for
the rfx_900),
.base.atr_txval=0 ------> .base.atr_txval=MIX_EN | ANT_SW
.base.atr_rxval= MIX_EN --------> base.atr_rxval= MIX_EN | ANT_SW

However, will this a) work, that is allow me to use the RX2 port to
recieve and b)
will it fix the problem shown below when I insert the call to
self.subdev.select_rx_antenna('RX2).
Any help would be greatly appreciated.

Traceback (most recent call last):
File “./usrp2_fft.py”, line 275, in
main ()
File “./usrp2_fft.py”, line 271, in main
app = stdgui2.stdapp(app_top_block, “USRP2 FFT”, nstatus=1)
File
“/usr/local/lib/python2.5/site-packages/gnuradio/wxgui/stdgui2.py”, line
36, in init
wx.App.init (self, redirect=False)
File
“/usr/lib/python2.5/site-packages/wx-2.8-gtk2-unicode/wx/_core.py”, line
7836, in init
self._BootstrapApp()
File
“/usr/lib/python2.5/site-packages/wx-2.8-gtk2-unicode/wx/_core.py”, line
7433, in _BootstrapApp
return core.PyApp__BootstrapApp(*args, **kwargs)
File
“/usr/local/lib/python2.5/site-packages/gnuradio/wxgui/stdgui2.py”, line
39, in OnInit
frame = stdframe (self.top_block_maker, self.title, self._nstatus)
File
“/usr/local/lib/python2.5/site-packages/gnuradio/wxgui/stdgui2.py”, line
60, in init
self.panel = stdpanel (self, self, top_block_maker)
File
“/usr/local/lib/python2.5/site-packages/gnuradio/wxgui/stdgui2.py”, line
81, in init
self.top_block = top_block_maker (frame, self, vbox, sys.argv)
File “./usrp2_fft.py”, line 112, in init
self.subdev.select_rx_antenna(‘RX2’)
File
“/usr/local/lib/python2.5/site-packages/gnuradio/gr/top_block.py”, line
94, in getattr
return getattr(self._tb, name)
AttributeError: ‘gr_top_block_sptr’ object has no attribute ‘subdev’