I have and older tivo which coax out of tivo to the tv. I have a hdtv now and I am wondering if there is such a cable that allows you to go from tivo coax out on one end and the other end will be and HDMI connector to the tv.
I don't think there is such an adapter if you mean an RF coax to HDMI. Not any real advantage to connecting this way since the TIVO boxes are not HD. Try connecting them with whatever AV connections they have instead of RF since that will give you the best SD picture they are capable of giving you.