The tv Must Have a 'Broadcast Tv Digital Tuner' also known as a ATSC Tuner , to receive the the Broadcast Tv Digital signals. Is this a older tv?? what is the make and model number?? If the tv does not have a Broadcast Tv Digital Tuner then a converter box is need to receive the digital signals.
http://forum.tvfool.com/showthread.php?t=380. If the tv is Really Old then it might be best to get a new tv.