Where is the receiver antenna on the car for the keyless remote?

Mine sucks. I can be 10 feet away press the button 5 times, and the passager door won't be unlocked. Also I have a convertible, and when I hold the button down it take forever to make the top go down. And sometimes even when standing right next to the car it only goes down half way.

geno

In the hardtop, there is a plastic piece that looks like a speaker in the center rear of the headliner - I think thats where the receiver is. Not sure on the convertible though.