I am beginning to have a few suspicions regarding embedded window antennas. In my G35 I have an antenna amplifier. This is switched. So if you install an aftermarket radio and not hook the amplifier up to the ignition circuit from the new radio, it will never power on. I also suspect that it is very possible that if you turn the factory head unit to a different function, such as CD or Satellite radio, it very well my turn off the antenna amplifier since it is not in use. Both of these situations would make using the factory embedded antenna unsuitable for anything but the factory radio. Don't know if this is the case with all embedded antennas, but just my 2 cents.