Remember whenever you use a coax splitter your literally cutting the single strength in half. We had this same issue at my house when I was growing up in Marin County. Our house was very long, not tall but long so the entry point for the cable in my room was 500 feet from where the cable connected to our house. We than had eight outlets throughout the house, but the way it was done had many splitters - in some cases 3 splitters before the cable box. WE would constantly get this channel is currently unavailable. Comcast came out and installed a single booster at the entry point. It literally pumped up the single enough for the capacity we had and adding one more port would F up the picture. Also adding end caps to your coax cables that are not in use help improve your overall single since the single isnt being lost at the end of the cable anymore.