Yes you can, I did it once when I was using two head units (one for cd and one for tape) I liked having both tuners hooked up because it gave me many presets this was before empeg came along. I think I still have the adapter sitting in my tool box. Anyhoo rat shack has what your looking for I can't find a link for it but its a y adapter for motorola plugs (thats the standard car ant. plug) unless its the mini one which they have adapters for them too. If I find a link I will post it.

Ben