I have my aerial connected to the youview box RF in socket, and my TV aerial socket connected to the youview box RF out socket.
My tv works fine on its own tuner even when I don't have RF loop through set to "on" on the youview box. It even works when the yuoview box is in standby or powred off. So my question is "why does this work without having to set RF loop through to 'on', and without having to have power on the youview box?"
My TV aerial actually comes into another room where I have a powered splitter. One of its outputs goes under the floor to the room where my youview box and main tv are located. I guess that the splitter is boosting the signal enough to satisfy both the box and the TV without further boosting in the youview box.