The radio waves can exert force upon an object that they hit, but they don't have any mass to push the emitter in the opposite direction. Is this what you two are saying?

If it is, then couldn't you put the radio emitter on the front of the spacecraft and let the radio waves hit some sort of sail to pull the ship along? I just don't understand how the radio waves can have the mass to push an object they come into contact with, but not enough mass to be used as reaction mass.

Very simple diagram (I hope it turns out)
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/

Ship ====

Radio waves ~~~~~

Lee, (Let me know were I'm going wrong here)