Update on my FM transmitter.
I refunded the expensive transmitter that was making music terrible and bought on Amazon $9 LDream transmitter.
Small gizmo plugs-in directly into my laptop and recharge from USB cable, while giving very good sound transmission.
Original camper stereo has lot of adjustments, so fading bed speakers out (dogs sleeping there were getting spooked) and balancing my speaker higher then wife speaker, turning tre to max made me happy camper.
Sure not good enough for classic music, but good for movies watching.