All channels are not getting Tuned

[anilsadhineni]

TV not picking up signal for channels, I can see Ten, ABC, TVS tuned, but not ONE, Nine, Seven channels are not getting scanned. What could be the issue, I'm using LAPD antenna fixed on the top of the roof at my home. I'm using Sony LCD Bravia TV. Please HELP

 

[popatim]

use tvfool.com to determine antenna aiming, size, and what station you will be able to pick up.