Chris, I am not familiar with the SAT520 directly but you should be able to get the OTA signal to your HD receiver either through the 5x8 multiplexer or directly into the HD receiver. This would be dependant on where your antenna is located. If you can receive "good" reception for the analog OTA signal for the channels in your area, then you should be able to get the digital HD signal for that same channel since most stations broadcast from the same tower (not always at equivalent power if they are in startup mode). Since the D*Tivo's don't deal with the HD signal, you should be able to keep the two processes separate (you will have separate "guide" info from both the TIVO and the HD receiver). When you set up your SAT520, there should have been a "start up" process that downloaded channels available in your zipcode from D*TV and gave you options to scan for both analog and digital TV broadcasts. That process should have pointed to what channels the 520 was able to locate since it would build them into the guide. I would debug with the Silver Sensor directly connected to the HD receiver to eliminate any variables related to diplexing the OTA channels from the coax feed from the multiplexer. Good luck.