You need to get an RF modulator, these can be had from most electronic, TV, aerial and online stores.
I believe you would need an RF Demodulator, or an RF tuner. Similar to that of a tv tuner just instead of hooking up cable you would want to obviously hook up your antenna. For the output of the tuner (demodulator) you can hook it up through just about any means, including RCA cables, phono cables, etc...
if you do need to go from an antenna to rca jack, the best and cheapest thing i have used is just a vcr, has coax input and your rca outs!!