Audio Systems: car radio, antenna amplifier, factory antenna

Question
QUESTION: my AM receptions cuts out completely after the car warms up~~~10 minutes.  I have an Acura TL with the antenna in the winshield

ANSWER: do you have rear window tinting ?



---------- FOLLOW-UP ----------

QUESTION: no...no rear tinting.  After the car warms up, the AM cuts out...we tried two different radios so we know its not the radio

Answer
near the back window on the side there is a factory antenna amplifier booster
this device is the problem in your vehicle  find it and replace it
to be sure buy a $10.00 from your local auto part ( not the ruber antenna )
pull the radio out and install it ,just put it in the roof or the hood and test al the stations for 20 minutes
good luck