I need help... do they have it and where can you get it?

OK. I got a DVD Recorder/VCR Combo from Walmart but the downside is it is line out/in only meaning it doesn't have an og OR a Digital Tuner period! So I went to goodwill and found one of those cable boxes from the late 80's or early 90's that were used on TV's without a cable-ready tuner on those really old T.V.'s (I only have basic cable). I didn't know it didn't have A/V outputs on the box because I purposely bought it to record programs for the DVD Recorder. So I've been using a broken VCR with an og tuner on it and I record programs to the DVD Recorder. So the question is I know they have an RF modulator that converts A/V signals to a coax cable but is there anything that can convert an RF signal into an A/V signal? If there is where can you find it? Thanks!