$9.00 set of rabbit ears from Radioshack with a UHF loop; any "special" HD antennas are a waste and a rip-off. OTA HD is either UHF or VHF, no reason for a special antenna unless you're going for an amplified antenna or a directional antenna. Get a pair of rabbit ears and a UHF loop for $9.00 and see how many stations you can get OTA.
I'm rural so I can only get ABC about 20 miles away. The other stations are about 60+ miles away with low-watt transmitters so I'd need an external mast antenna with a directional motor.
for information on antenna type, tower locations, frequency, and azimuth. You only need to put in your zip-code so don't worry about the other information fields.