how can i fix the signal on my alba box ?

It depends on what you mean by your question. If the box is reporting no signal it could be one of two things:

1) the Aerial - check the aerial, it's alignment and the cables and connectors. BTW Freeview needs an outdoor aerial. Indoor and loft aerials seldom work.

2) The box - try the box on an aerial that you know works OK. If it fails then bin the box and buy a new one. Budget boxes (like yours) are uneconomic to repair.

T
January 2010