Adding rca jack to old Mini (1986) tv

I have an old mini TV made in 1986. I'd like to use it as a security monitor. my security camera has a RCA cable that I'd like to attach to the TV. The TV only has one input on the case, it's for a external antenna. I think it's a 3.5m, it says 75 ohms next to it. can I get an adapter for this to attach my cable, or can I pull the case apart and install a RCA jack on the back on the TV? if so how do I do this? Any help you can give will be appreciated. Thank you.

Modulator. Like this. **broken link removed**

Thanks, it works now.

Thanks for the help with this little project. I went to the local Goodwill and found a RF modulator (looks new) for $3, they also had a cable the converted coax to 3.5mm, which was great. It works now and I love it. Thanks for pointing me in the right direction.