Antennas are the lenght they are because they resonate at their design frequency naturally. They are tuned so to speak. A quick formula for calculating the resonate lenght. 234 / Frequency in Mhz. = lenght in feet. FM radio goes from 88 to 108 Mhz. A 1/4 wave antenna tunned mid band would be 234 / 98 = 28.6 inches. Antennas which are to short will have more capacative resistence than they should. This can be compensated for by adding a measured amount of inductance (a coil). This will bring the system back into resonance. However the shorter wire will have a smaller capture area and will therefore be less efficent. In Metro areas where the transmitters are close by you won't notice. If you live in the out lying areas, you most likely will notice the loss of sensativity. But they are easy to swap out. Keep your original in the trunk for when you find youself on those road trips. Or just use Sirius/XM.
Works good even out on the sticks.
Finally ordered my 8 inch shorty antenna 
(Mods in profile)
2007 VISTA BLUE GT! Only Mod so far is the 14" shorty antenna and a billet plug with GT on it for the dash power plug.. No Engine Mods 'cause I like the car fine the way it is and making it faster is only gonna get me in trouble.
