I am experimenting with a masthead amp to improve UHF reception. I have a Sony TV with built-in UHF digital tuner and an old Chinese digital UHF box that I am using for tests. For some reason the antenna power on the Chinese box does not seem to work. The TV also doesn't have it. So I have made my own power injector using a piece of coax and a 9 volt battery. This seems to be working on the Chinese box.

Before I attempt a permanent solution on the TV, I need to know if putting 5-12 volts across the antenna cable can damage anything in the TV, or if I need to add a protective diode, and if I do, will that affect the RF signal? Answers to these questions would be much appreciated.