At tvfool.com you can get an analysis of what OTA signals are available at your address. Here's what the output looks like:
I only recently learned about the site so I don't have deep understanding of the chart yet, but there are directions on the site. The circle is directional for the channels in the table and the colors are the type of antenna you are likely to need to pick up said signal. I think Green equates to the paper clip shown above.
At a high level I think it means my attic antenna is orthogonal to optimal orientation... figures.
-Rob
-visit http://www.kahr.us to get my daughterboard that helps fix WPC pinball resets or my replacement LED display boards for model H & model S Skee Ball