jremington:
Try 17 cm of straight wire.
Ye but what if the range will increase ?, and if not, i'll still not be able to transmit the RF signal from the back of my car.
I'm thinking of moving the whole receiver using a long 3 wire, wire (5V, ground, signal) in the middle of the car, is there a problem because the length of the signal wire will be > 3m long ?
I'm also thinking of attaching the antenna to the antenna of the car radio but this might be the stupidest idea if the antenna have some sort of 12V in it 
right ?
What would you do ?