When I tune the iTrip, I only hear silence on the radio!

This is generally a communication error between the iPod (usually a Nano) and the iTrip. Simply reboot the iPod while attached to the iTrip. Hold the MENU + Center Select buttons together for about 6 seconds - until the iPod shuts off. You can let go of the buttons at this point, and the iPod will boot back up, with the Apple Logo on the screen. Once the menu screen comes up, you should be able to select a song, and hear it playing on the radio.