Antenna question

[Roguish Lawyer]

The radio antenna on my Escalade is so long that it hits lots of beams and things in parking structures. The top of the antenna was torn off and I want to replace it with a shorter antenna. Apparently there are variety of shorter antennas I can buy to avoid this problem. My question is whether reception quality will be impaired if I go with a significantly shorter antenna -- is longer always better? Any other advice?

Thanks very much for any suggestions or comments.