If you set your transmitter to PCM mode, it will work. If your transmitter is not on the correct channel, then just obtain a Futaba FM transmitter crystal on the desired channel. There is no such thing as a "dual-conversion" transmitter crystal. "Dual conversion" applies to receivers, only. PLEASE NOTE: This is NOT legal for systems being used in the U.S. Other countries will have different regulations, you MUST check with your country's radio ministry/administration for the proper regulations.

You could also put in a Dual-conversion FM receiver crystal into the receiver that's on the transmitter's channel. Please note that you must make sure it's a Dual-conversion FM crystal for the receiver.