iPod Car Stereo Installation Guide
"Wired FM modulators
To install a wired FM modulator, first find a good mounting location. Keep in mind that you will need to access your factory radio's antenna input, and connect the iPod to the modulator. Common locations include under a seat, behind an interior panel, and in the cavity behind the receiver.
FM modulators require a 12-volt connection to a switched (on/off) source. Since you have to remove your radio to get to the antenna input, you'll have easy access to the power and ground wires in your factory radio harness. If you don't want to splice into your factory wires, you can make the power connections at your fuse panel. Look for empty fuse holders and insert fuse taps. You'll also have a black ground wire that must be secured beneath a nearby screw that makes contact with bare metal on the body of the vehicle.
Following the instructions on your Crutchfield MasterSheet™, remove your receiver from the dash and unplug the antenna from the rear of the unit. Plug the vehicle's antenna cable into the antenna input on the FM modulator. Next, run the output of the modulator to your receiver's antenna input (certain vehicles require antenna adapters — use the online Vehicle Selector or call a Sales Advisor to inquire about a specific vehicle). If this leaves slack in your antenna lead, tie it up so it won't fall down and interfere with anything.
Most wired FM modulators accept RCA inputs, so you'll need a minijack to RCA cable to connect your iPod. Once you have connected the iPod, determine which of the available modulation frequencies is least likely to be shared by a strong local radio signal and set it on the hideaway box before you mount the unit (on some models you can change this setting on the fly)."
Evidently it offers MUCH better sound, as the signal is sent from your iPod directly to a converter and through your stock radio's antenna port on the back of the stereo. This might work for you.
