Good question with all the converters available for so many things. Like Scherrman posted I don't think there is but interestingly there is an HDMI to coax converter but I don't think it works in reverse. And that is meant for an easier way to extend HDMI but it has to start with an HDMI (Digital) signal, goes to the Coax converter, then up to about a 400' run of coax connects back to a an HDMI converter. All that is happening is a digital signal is being run over coax. But you can't start with an analog Coax signal and make it digital HDMI that I am aware of.