x to hd

hey guys,im lookin for sumtn that will give me hd quality,from a *** hd box,problem is *** box is in different room to tv with only coax between,so obviously quality aint great and seems ders a full hd subscription its only a balls,anybody have any ideas,its not really possible to get new wires from a to b otherwise id just get an extended hd lead,,,thanks in advance