[Hendog]

The idea behind an external antenna is that the enegy received and also radiated to/from are not encumbered by the surrounding metal and glass as experienced with the antenna inside the car (the antenna on your handheld cell phone for instance). Mounting an external antenna "that you'll (discetely) install in" your P-car is counter productive. You can't get away from having your antenna outside to gain the advantage. Small magnetic mount antennas are available. The antenna is approximately 2.5 inches (approx quarter wave for 850 Mhz, half wave for 1800 Mhz) and the magnet mount is about the size of a silver dollar or less. At least with this set up you can pop the antenna on your roof when need be for maximum performance and remove it when you're done. Just make sure you have a good clean mag mount base and roof so as not to scratch anything. You can even put a piece of tissue between the two and still get great adhesion. Check with your local cell phone shop, they should carry these antennas.