Yaamon, you have more tests to do! (the fun never ends
) because you need to see if there is now a risk of the preamp overpowering the ATSC tuner (snow, distortion, etc.)
1. get the preamp installed and powered up
2. on TV #1 leave the ATSC tuner's signal strength meter on the screen on one of the weaker stations and do the following steps as quickly as possible
3. disconnect TV #2's antenna feed from the splitter while TV #1 is up and running and note the signal strength difference
4. now check all DTV and analog channels on TV #1
5. get TV #2 hooked up again as quickly as possible
During #3 if you notice a sharp jump upwards on the meter to 100% on such a weak station you are possibly at risk of overpowering your receiver. Imagine stations that were already at 100% now getting that power boost and you start to see the problem. If you have such a situation you will need to install an attenuator on TV #1 so that in the future if TV #2 is ever disconnected for more than a small amount of time you will avoid overdriving TV #1's ATSC tuner.
Another scenario: if in the future you decide to further split the connection into a DVR or VCR or FM Tuner you can do all those steps again to see if its time to remove the attenuator from TV #1.