My 19 Inch Digital Tv Has Rabbit Ears; Do I Need a Converter Box? or an Antenna?

It is a Sharp LCD 19 inch with built-in DVD player. I am pretty sure it can receive digital signals since I can request a digital channel and the menu gives me the strength being received. Currently, they are all zero no matter the channel selection. The problem is that it says something like "the signal is too low; please check antenna hookup". Would a converter box be the best option or another antenna?

Suggestion:

76 days left of analog, to be exact. Go to http://www.dtv2009.gov/ for all your questions and get a coupon while you are there. It is the official site and should offer everything you need. After February, no antenna will work.