I can't work out how to change the default input...

Question

When I turn this television on, it defaults to the terrestial tv input (which is blank as we don't use it). I've tried playing around within it's menu to change the default input to the cable tv channel (AV-1) but I can't make it work. What I'd like is when I turn it on, I don't have to change the input each time - it's annoying. Also - why the heck doesn't the "smart" mode work detecting 16:9 v 4:3 aspect ratio.Any help appreciated.