Car radio reception - how to enhance

I installed after market Pioneer head unit in car from Echo sound, the radio signal is very poor. The installer said that the drawback of the aftermarket unit is radio signal will be very poor. Now the radio is useless, How can we enhance/boost the radio signal to hear it clearly? What device to add, where to modify.

Since Echo sound is very far, i was looking for someone having knowledge in this field and who can suggest what device to buy.

Thanks in advance