Originally Posted by spacewolf
My main question is understanding how the antenna and cable tv frequencies would interact if both were connected.
Hello, spacewolf; welcome to the forum.
DrDon is correct; you must not mix antenna and cable TV frequencies because they overlap and will interfere with each other, and your antenna will radiate the cable TV signals coming through the inadequate port to port isolation of the combiner. This is called Cable Signal Egress, which is illegal.
Your diagram shows cable TV signals coming up from below, and antenna signals coming down from the antenna to the TV. Since you would have two sources of TV signals, you wouldn't be using the splitter as a splitter, you would be using it in reverse as a combiner.
The suggestion by DrDon, using a wall plate with two F-81 connectors, would allow you to choose how your system is wired and avoid having a splitter in the wall.
If you have cable and antenna signals at that dual wall plate, you can use an A/B switch to select which signals you want to use for the TV.
If you drop cable TV and want only antenna signals for all your TVs, then you can use a splitter to send the antenna signals to the TV shown and also down to other TVs. That splitter would be connected to the wall plate outside the wall.
Before you get too far into this project, you need to find out if the antenna will be able to provide the OTA signals you want.
Have you done that?
You also must not combine OTA signals with cable internet signals because your antenna will radiate the cable internet signals coming through the inadequate port to port isolation of the combiner.
cable modem operates on what frequency?