I have an older Sanyo TV. It only has a coaxial hook up in back, but I want to hook it up to my Directv. Is there some kind of adaptor I can get to make this work?

If a source only has stereo and composite video outputs and you want the signal on a device that only has RF input, you will need to purchase an RF modulator. Ask for one at consumer electronic dealers or video game dealers (there may be some overlap)