In a few weeks, the roof on our house is being replaced. Obviously, this will require removing and reinstalling our roof antenna, and I see this as an opportunity to get things done right.

Our current situation is that we have both a VHF and UHF antenna on the roof, connected to a diplexer box. I believe the UHF antenna is an old Sky installation. We cannot, however, receiver either Freeview HD or any of the analog UHF channels (Prime, Maori, etc). I do not know if this is due to problems in the antenna itself, its positioning, the diplexer or the cabling. Analog reception of TV1/2/3/4 is fine.

Is there an official standard for new roof antenna installations, and what's the best way to go forward? Should we try to reinstall the existing setup, or just the existing UHF antenna, or buy a new UHF antenna? What about the cabling? Advice would be appreciated.

The location is St. Johns, Auckland