sometimes it works not good but i can receive radio but after rain it's difficult for me to receive fm radio: could it be the aerial amplificator on the base of the antenna that could be wrong ?

 

Do you have a model with the FM antenna on the roof? The gasket dries out and loses its seal, and water can get underneath into thew housing. This will cause some rust on the ground fitting.

When it gets wet, the dampness allows the antenna element to short to the ground, and attenuates the signal.

It is simple to disassemble and clean the connections.

 

Yes, i have a model with an antenna on the roof. Can i change it with something else like a shark fin ?

 

Yes, no problem!

 

Can i use a shark fin from any mark of vehicle like a bmw one or something else that i can find in a breaker