I've had a problem with my youview box for a while now that I've been unable to sort.
My setup is my aerial goes into my attic which has a splitter/booster with 1 input to 4 outputs (I did not buy this device so unsure exactly what it is, was left by previous owner of house. It is now boxed in after attic converted but I could get to it with a bit of effort). There are 4 outputs which feed 4 sockets, of which I only use two.
My TV socket in the lounge is the one I am having issues with. When plugged directly into my TV it works no problem, full channels and no problem with signal quality. When I use the youview box however it picks up only a few channels and the signal quality on a lot of them is very poor.
When I plug the youview box into my TV socket up stairs, it works no problem. Picks up all channels and signal quality is ok. To add to the confusion I had a TV engineer come from BT to investigate, he tried replacing the youview box which made no difference - new one had same issues plugged into the lounge socket. The TV engineer reckoned it was a problem with the aerial but I'm not convinced. I think it's more likely to be a problem with the splitter/booster in the attic.
Any ideas what I should do to resolve this issue?
If the Youview box picks up all channels upstairs then it is unlikely to be the aerial. It could be the cable from the box to the lounge or the socket from the booster into the cable to the lounge. Take the plugs apart at the end of the cable and make sure everything looks good and is secure. Refit and tighten then recheck it. Try the cable in one of the free sockets to see if that makes a difference, although an unused socket may have become corroded over time and be just as bad.
I should also have said. Swap over the two plugs at the booster and see if the problem changes from the living room to upstairs which would prove the output feed from booster to the living room is the problem.
The key point to me is your comment "When I plug the youview box into my TV socket up stairs, it works no problem" and that points to a cabling or connector issue. Your TVs sound as if they are both OK which tends to suggest the splitter and cabling down to the sockets will be OK.
My question is when you did this test upstairs, were you using the same aerial lead as when you tested downstairs?
The centre pin of the aerial socket on your TV and on the input socket to your YouView box is female, and when you look closely, it is split in half to give you contact pressure on the centre pin of the fly lead. It might just be that the pin in the lead is loose or tarnished and it just happens to work in the TV connector but not the YouView.
Another thing to consider is when you plug the co-ax into the YouView box downstairs, is the co-ax nearer to any possible sources of interference such as power supplies (e.g. the YouView box PSU) and mains cables. A lot of co-ax fly leads are cheap and nasty with a loosely woven copper wire screen - and they will pick up interference quite happily if they are near enough to a source of it - as sometimes happens when people cable-tie things up neatly behind TVs and the like.