[rabbit73]

Using a splitter from the antenna to feed the upstairs TV will work. Using the other side of the splitter to feed the whole house system might not work. We don't have enough information about the whole house system, like how many rooms are being fed, if there are other splitters in the system, and how it connects to cable.

Normally, the antenna should go directly to the point where there is a splitter for all the rooms, and it connects to the input of that splitter, not one of its outputs.

You must not have the antenna and cable connected to the same system.