Can I connect a TV antenna directly to a new TV or do I need a converter box?

I recently installed an old fashioned roof antenna for a customer. The customer had a new TV. I connected the antenna to coax cable, with the transformer supplied, and then connected the coax to the TV. I could not receive anything. I then installed a converter box between the TV and the coax cable and it worked fine. So my question is: Do all TVs require a converter box to receive HD broadcast from the air?