A signal booster is likely to help but is unlikely to give a perfect picture. You need to have your own aerial fitted or the communal one upgraded. Connecting to an existing satellite dish will only work if your tv has an integrated satellite receiver. There are basically two digital technologies: via standard aerials and via satellite. Which does your tv use? An internal aerial will be useless. Fitting one in the loft is a possibility but it will receive a weak signal due to the roof.