There's a device on the dish called a Low Noise Blocker (LNB). It grabs the signal off the dish and sends it down the COAX to the receiver. This is the only item on the dish that's even powered and even now it's only powered by a smaller current coming from the COAX. I can't see this causing interference. Other than that, the dish is a big piece of metal. I can't really see this being an issue unless it's in an area blocking the signal from coming in the house.
Maybe within a 10 foot radius I could see this as an issue, but I could see a specific type of insulation or building material being a larger culprit. What happens when you goto the furthest place in the house away from the dish?