Digital TV actually gets along with lower signal levels than the old analog TV. That's because the data stream uses an error correcting code, and because the bandwidth of the signal is narrower.
There is no such thing as an HDTV antenna. Antennas cannot tell the difference between an analog signal and a digital signal.
As a quick and dirty test, hook a short piece of TV cable to your antenna jack, and 2-3 ft piece of wire to the coax center conductor, with the free end of the wire attached to the cable outer conductor to form a loop antenna. On the TV menu, choose the antenna as your input, and have the TV do a scan to see what it detects. If you can detect a few channels, that's very promising.
A good general purpose antenna for HDTV is one with two "bow ties", one above the other, and a reflector screen behind them (~$50). If your channel detection test didn't detect anything, you may want to go to a four bow tie antenna.
You will almost surely want an amplifier at the antenna. They are cheap, and they get their power via the coax. They are important because coax is fairly lossy at UHF, and without an amplifier, only a fraction of the signal will make it down the pipe to your TV.
We ditched cable. We enjoyed it, but not $105 per month worth. We're happy with free broadcast TV and Netflix and Amazon Prime.
This.... HDTV antenna is a marketing ploy nothing more..
