I heard someone get TOLD for not understanding how antennas work in the mobile. It is very simple once you understand the following diagrams. This is something that is not taught in the typical ham class. You need a copy of the ARRL Mobile Handbook from the 50s to fully appreciate some of the cutting edge research done.

An easy way to validate this and to aid in antenna tuning is the Field Strength Meter and it will help you see the antenna pattern.