An off-air antenna is a product people use to receive over-the-air signals from broadcast TV stations. In order to use an antenna, your television must have a built-in tuner or you must have an external tuner connected to the antenna and television.
Digital or HD Antennas
There really is no such thing as a digital or high definition antenna. The Federal Communications Commission (FCC) says that anyone owning an antenna that is capable of receiving analog signals should be able to use that same antenna to receive digital signals.
As a result, I suggest that you try using your old antenna before buying a new antenna marketed toward HD reception. If your current antenna doesn’t work then you might need one with amplification, which helps the antenna pick up a better signal.
Amplified antennas electrically increase the ability to receive a weak signal. These antennas are especially good for people living in rural areas because the incoming signal might need a boost.
“Amplification is also needed in situations where there is a long cable run or several splitters between the antenna and TV,” said Ron Morgan, technical support analyst at Channel Master. “To increase signal strength proper antenna selection is key. If you start with the incorrect antenna, you will be fighting a losing battle.”
Indoor v. Outdoor Antennas
One could argue that a $20 indoor antenna works just as well as a $100 roof-mount model. It all depends on where a person lives in conjunction with the strength of signal coming from the TV towers.
According to Antenna Web, a site managed by the Consumer Electronics Association, good antenna selection is not just based on distance from the transmitting station. It's also based on accurately characterizing signal conditions and selecting an antenna that works in that situation.