If it's going to be connected to a CATV source. Otherwise, an ATSC STB would be needed, but it would have to be an HD one to get an HDMI output.
Sounds like that's what the OP is trying to do. He has basic cable, but either all of the QAM signals are encrypted or there are traps on his line limiting him to analog only. Sounds like he was sold a QAM tuner and a scan only picked up the music channels.
why not get a settop box from your cable provider $5 per month although some provide a free option. Also you could get a TiVo and cable card usually around $2 per mo. What is an Anntena company? Just buy a anntena from store no monthly charges but also no ESPN and such.