With an inverter (not a generator) the idea was to use a "chassis ground" to the RV frame, separate from the input DC pos and neg wires from the battery (but battery is itself neg grounded to frame--never mind that!)
Another trick is/was to braid the pos and neg input wiree to the inverter to cancel out their effects.
So--with the generator running 120v in the rig to run the CB radio, what is the actual set-up? Is there an inverter involved? Any DC where you can braid the pos and neg wires? The radio must be DC? Is it grounded to frame?