When I switch my TV to terrestrial channels i get no signal. I have a powered 'amp' or something in the loft where 3 internal tv cables come in and then the aerial cable from outside comes in. Then on my aerial pole outside I have the internal cable going into a box and the box has a cable going up to the aerial. I recently noticed this box had fallen down and had filled up with water so wandering if it now 'broke' its an Antiference UPF25U and i just want to replace it but cannot find one maybe too old. What can i replace it with please.