“ I'm noticing that any television I have hooked up where my portacolor is (this is only happening in one location at home) experiences vertical loss and bouncing periodically. Nowhere else in the house is that happening, and it's only happening on over the air transmissions. “
Sounds like the portapottie is generating a bit if rf interference that is bothering the other tvs... likely in an area of the house with the weakest signal from the modulator.
Might try a snap on ferrite filter on its line cord, it might be helpful to bypass its power supply diodes with high quality caps, 10 nanofarad or so.
jr