I just bought an antenna for Rat Shack. We already have a Satellite so to simplify the wiring, I bought two Diplexers. They were $20 each. That seemed expensive, so I just did a search on Froogle, and found them as cheap as $2. Are they all the same? Should I return the two to Radio Shack and buy the cheapest one I can find? If not, what do I need to look for?