I chuckle when I see "HDTV antenna" on boxes near expensive TVs at electronics stores. We're watching great digital TV with nothing more than a $20 antenna, an old-fashioned dipole (rabbit ears) with a loop in the middle.
Granted, our reception improved immensely this week with a move across town. The digital broadcasts are now coming in as clear as any cable or satellite signal, with no more antenna fiddling as we change channels. All it took was moving a few miles, and more important, out of a creek valley, to get a better TV signal. Even a balky Humax tuner that we attached to a standard TV manages to pull in all the digital stations in the St. Louis area. If we had stayed in the valley, a rooftop antenna would've probably gotten us good reception.
By the way, it wasn't really the rabbit ears that we'd have to pivot to get a better signal. Digital television currently broadcasts in the UHF band (channels 14-69). Stations still ply their analog wares on the VHF band (channels 2-13). So it's the little UHF loop that sits between our cheap rabbit ears that pulls in the digital signals.
There is no such thing as an HDTV antenna, despite some advertising claims. Any antenna that can pull in a UHF signal works for digital television, including the high-resolution HDTV signals. For most urban dwellers, an inexpensive indoor antenna like ours will do the job. Some may need a bigger antenna, or even one mounted on the roof. And a home outside a valley helps.