Maybe an HD set,possibly a freeview hd unit.HD and on freeview will be the first to suffer if you have any signal worries,in fact a lot of people do have this capability on tvs they have just bought.
If your signal conditions doesn't allow it to be tuned in you will have no idea of its existence.
And if you are thinking of getting freeview hd then have your signal checked out to make sure you can receive it.