Modify Baseband into Bandpass

I want to modify the MIL-STD-188-110B Baseband demo into bandpass mode. On either side of the channel, I placed a product bus combining the Baseband signal with a complex sine wave. I used sample rate of 1/2400, per frame 40, and 1800 Hz (+ on the transmitter and - on the receiver side). I also placed an audio writer so I could hear the output.

However, the waveforms sounds the same with the sine wave combined with the baseband or commented out, so I'm doing something wrong. How should I modify the baseband signal so that it is carried on a sinusoid of 1800 Hz? Thanks for any guidance.