Connecting STB with RF

[sudhirbhosale]

Hi
I want to connect setop box using RF as Audio L R I want to utilize for radio listening. I have below doubts:
1. What are consequences to quality and safety?
2. Can I use same RCA cable for RF connection or dedicated required? As RF indicated with 75 ohm
3. It also has RS 232 out but I guess its only for video. Am I right?

Thanks