Problem in usrp side selection

hi all,

I have made a simple program for sine transmission which is just a
replicca of usrp_siggen. Im successful in transmitting a sine wave
with the help of side A of usrp1, but when i want to transmit it by
side B, it doesnt give any error but it doesnt transmit either…

My code is given as:

from gnuradio import gr, usrp

class my_top_block(gr.top_block):
def init(self):
self.u = usrp.sink_c()

    #self.pick_subdev = usrp.pick_tx_subdevice(self.u)
    self.pick_subdev = (1, 0)
    ########### here the code works fine if i pick side A in that

case self.pick_subdev=(0,0), but when i select side B as given in the
code, it doesnt work

    print self.pick_subdev
    self.subdev = usrp.selected_subdev(self.u, self.pick_subdev)
    print self.subdev
    r = usrp.tune(self.u, 0, self.subdev, 2450000000)
    self.siggen1=gr.sig_source_c(1000000, gr.GR_COS_WAVE, 10000, 
  1. self.connect(self.siggen1, self.u)
    print “Using RX d’board %s” % (self.subdev.side_and_name(),)

def main():
tb = my_top_block()

if name == ‘main’:

kindly help me on this