Need help on transimit a band signal

hi
in grc,i have a problem,i want to trasimit a band signal with the grc
's block,but when i tansimitted it,there is something wrong with it.in
the receiver,it is only a frequent point signal.so it indicate that the
trasimitter is wrong.i guess the usrp sink do not do a goog work.so how
can i do with the usrp sink to have a band sink. i am looking forward to
your reply.
thanks!

What is the amplitude of the digital samples going into the usrp sink?

For usrp, the max amplitude is 2**15. Try an amplitude around 10e3
For usrp2, the max amplitude is 1.0. Try an amplitude around 0.1

-Josh