I'm not an antenna expert, but I don't think it would be a good idea to try to mix the antenna and cable signals. The problem is they may interfere with each other and you won't be able to see either one very well. If you want to try it, get a 'cable splitter' and run it backwards: connect antenna and cable to the 'outputs' and connect TV to the single 'input'. If it works, great.

If this doesn't work, it would be better to run a separate cable from the antenna to the TV. If there are two antenna inputs on the TV (usually labelled A and B), you can switch between sources with the TV remote. If not, get an 'antenna switch' to set next to the TV and flip it as needed.

This may be a bit cumbersome with an attic antenna and two TV's. If you're handy you could run cable inside the walls to the outlet boxes, and replace the single outlets with double outlets - labelled as to which is which, of course.

I plan to do the last option myself, because you never know when the cable will go down, and you can still see over the air in an emergency.

I guess I wasn't clear in my first post. My bad. I'm not trying to mix cable signals and OTA antenna signals. I'm trying to use the cable wires which are right now not carrying anything to send a signal from the attic antenna through the house to my two tv's. Can I do that?

The type of cable used for OTA signals and CATV signals is the same. As long as you don't mix your cable tv signal into your antenna, you can reuse the cable already installed.

Your HOA may be violating federal law by limiting your use of your OTA antenna on a structure that is for your exclusive use. See the link below for more details.

Here is a link that might be useful: FCC OTARD Rule

i have a lil cheap 22" tv/monitor on my desk

i use a channelmaster splitter/combiner connected to it...there is both a ota antenna connected and its connected to the cable line

i have to switch the mode on the tv between atsc and cable but yeah it works

i am able to watch local ota HD and also the cable