I have now tested further. It seems there is a BUG in the Pro-HD firmware (or the setup assistant). If, in setting up the Coax input using setup assistant, you choose "External box (cable box, satellite receiver, DVR, etc.)," no matter what channel you select in the window that pops up, the Slingbox will be configured to channel 3. You cannot select channel 4, 5, 21, 60, or any other channel and have it take effect. This means that if the external box (such as the Dish Network receiver) cannot send its output on channel 3, it CANNOT BE CONNECTED TO THE COAX INPUT OF THE SLINGBOX! I contacted Sling Support (after paying for support), and was told that they would report this problem, but that no assurances could be given that it would ever be fixed!