OTA signals require a receiver or tuner. If your tv is just HD ready, then yes you will need something to pull in the signals, in addition to the antenna.

The other night I was at Walmart, and noticed they had some off brand name HD tuner for like $150 bucks or so. I think I paid $250ish for my Samsung OTA reciever.

Some services like Direct TV and Dish, etc. offer to give you the local stuff in HD also, but not sure if that costs extra or not on top of the regular service.

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