I have just installed DirecTV and also have Cable Broad band, my problem is that I want them both to run through the same cable. I know that I need some type of Diplexer on both ends to combine the signals and then another one to break them back out and I have tried a diplexer for Radio Shack but it didn't work. Is there some "special" type of diplexer that I need for broadband and if so where would I be able to get such a device?