App for making iPhone as a fm transmitter

without using any external hardware can I get my iPhone to work as fm transmitter. ?

I will then be able to play music on my iPhone and transmit to car radio. The iPhone will act as transmitter and the car radio as a receiver

i have iPhone 6 and ios12

i am already using small external device as a blue tooth +fm transmitter which is plugged to my car charger I would basically like to avoid using this external device.

Pl advise