It is your imagination. Digital cable is either ON or OFF. Typically you'll get a scrambled screen (pixilazation) if you have a week signal going into your cable box. If the picture is already there, and you increase the signal, the picture itself doesn't change, your signal levels just change. You can enter the diagnostics screen of your 4250 and check the stats on page 1 and see the difference when you add the splitter vs. no splitter. To enter the diagnostic screen, press the bullseye on the front of the box for apprx 5 seconds, you will see a "mail" light start flashing on the display, then press info button and you will see the diagnostic screen pop up. use page up/down on remote to scroll through.