HDTV Antenna for Converter Box?

Your old TV antenna should work just fine, if the connections are are good and it is aimed the right way. (the front has the short elements) Enter your latitude and longitude into the spaces provided in the web page below (there are links in the fine print at the top to help you figure out your latitude and longitude). When you do that, the web page below will give you a lot of information on the digital tv stations in your area, including their transmit power and direction. Use that info to make sure your antenna is aimed in the right direction to get the stations you are missing. A few degrees can be the difference between receiving a weak station and not. It might be that the stations you are missing aren't transmitting digital yet. Or, they maybe transmitting at low power until a new transmit sight is built or something. Antenna web is another source for similar information.

Your old analog antenna mounted on the roof was designed to receive specific frequency ranges that were/are being used for broadcast TV. The new digital broadcasts are -not- all within the same frequency spectrum your antenna was designed to receive. Some are, but not all. Getting a HDTV antenna is merely a new antenna designed to receive the new frequency range of HD broadcasts, and should work better than your existing roof top antenna. Some have automatic tuners built-in to electronically modify the physical length of your antenna collection area to adjust for the various frequencies. Think of using a CB radio antenna for your FM stereo; it will pick up some stations but not all - and not as good as a FM antenna. Or an AM Loop antenna. The "piece of metal" that is an antenna is very important for reception principles, typically engineered to be in 1/4 wavelength divisions of the transmitted signal. Too long or too short and your signal reception suffers immensely.