Liquid Diet 2 - I live in Amityville & tried an indoor antenna. The Philips Silver Sensor is probably the best indoor HD (UHF) antenna & cost $20 - 30. I'm on the fringe of reception range & really need a rooftop antenna. But with the Silver Sensor stuck in a hanging plant (for height) I'm getting digital channels 2, 5, and 7. Signal strenght on NBC 4 & WB11 is just to weak to get. FYI your TV needs an internal ATSC tuner to do this.
Re cablevision... If your HD TV has an internal QAM tuner you can get all locals - 2, 4, 5, 7, 9, 11, & 13(PBS HD) as long as you subscribe to basic cable. You DO NOT need a set top box OR the IO package to get the above channels. I subscribe to basic family cable and get CBS2.1, NBC4.1, 4.2, 4.4, FOX5.1, ABC7.1, 7.2, 7.3, 9, WB11, and 13HD. I receive channels 2.1, 4.1, 5.1, 7.1, 9.1, 11.1 and 13.1 in 720p or 1080i with Dolby 5.1 surround sound. The .2 are sub-channels like WNBC4 WX Plus etc.
Be aware that cablevision customer service will lie & say you MUST subscribe to the IO package & rent their HD set top box. I have spoken to them 3 times over the last few years, most recently in person. Each time even after telling them I have an HD ready TV w/ internal qam tuner they say getting HD is impossible without upgrading the box & paying another $10/month for the IO package. BS! FIOS here I come.
FYI you do need IO & a set top box or cablecard to get ESPN HD, Discovery HD, etc.