With all of this talk about the transition to digital over-the-air broadcasting, some things have gotten lost. There is some confusion about what needs to be replaced, or added, or whatnot.
First, you do not need to replace your TV; your TV will work just as well as it ever has, but unless it can receive the new TV signal you wont be able to watch any programs.
With current over the air broadcasts, which are called analog (because they’re simple radio waves), if you receive a weak signal it shows up as static, and you can try to tune in a better signal.
With digital broadcast signals, there is no ‘weak’ signal, it is either strong and bright or not there at all. If you live in a place where your current TV signal is weak, you will receive no signal at all after the changeover.
Consumer Reports suggests that if you receive the error message from a digital tuner(the add-on box you will need to receive the new TV signal) that says “weak signal” that you get a bigger antenna, move your current antenna near to a window, or to a higher point in your house, such as an attic, or buy a signal booster (which you can attach to the TV).
If you live in a Comcast service area, they are required to sell over the air channels at low cost (sometimes as low $11/mo); however, they are not required to tell customers that this service is available; you will have to ask for it.