The installer came this week to put in a triple LMB dish and install a HDTV antenna in my attic. However, he ran both signals through one cable and then split them with a diplexer (sp?) before running it into my HDTV tuner. I asked him if that would degrade the signal strength or quality and he replied no, because the two signals have separate frequencies. Although I am getting good HDTV reception, I wonder if what he's telling me is true. Thanks for your help.