Want to listen to FM radio on your iPod nano? You need to plug in a head set. The iPod nano uses the attached cord as its antenna, allowing it to pick up radio signals. Say you want to dock the nano and play its radio back on speakers? You'll still need to attach a cord of some kind to the earplug jack. A standard 3.5mm audio cable will do the job for you. Look for one that's at least 8-inches long.