Implementing an interference source

hi everyone
i am new to gnuradio, nowadays,i want to build an interference
source,but in grc,i just know grc a little and do not implement the
interference source.so can anyone help me resolve this problem or give
me some advices.
the interference source demands QPSK module,500K bandwidth,frequence
about in 440M.

thanks in advance.

See the “channel model” block.

-Josh