antennaweb.org has all the info you need to make the right choice. It also will tell you how high and what direction to point.

Easiest way to tell would be to pick up a new file and try it. If it works, then you needed a new file. If it doesnt, then you need to work on your technique.

They are intentionally making it difficult to see live. This way they can show you clips the next morning of only what they want you to see.