I want split hdmi, one will go to an HD TV, I need to down convert the other to SD and coax for SD TV sets?

I want to split my HD HDMI signal from one of my Direct TV HD DVR's, with one side going to an HD TV. What I'm not clear on is how to down convert the other side to a standard definition format where it can then be converted to a coax signal to back feed all of my old SD TV's used as monitors of the same channel.