Kitchen aerial point problems

I have an aerial point in the kitchen in a recently renovated house. The aerial in the loft has a two way splitter which sends from what I can see two wires down either side of the house. One aerial point is in the kitchen and we are having bad signal with it, especially when mounting the tv on the wall. I have bought a signal booster which works but I still don't have all the channels. What is stranger is that despite this being connected to the roof aerial, things in the kitchen cause it to loose signal. For example if you open the french doors to the outside, or if you have a clothes horse in the way. When you take the tv off the wall and place it on the kitchen table infront it gets a better signal? Signal in the lounge gets perfect signal from what we can tell. This has me stumped!