Hi all, have a great and safe year

I have an issue and need your help please.

Recently I bought an Android head unit for my X5 E53 2006 Navi (https://www.erisin.com/products/eris...-e39-e53-x5-m5)

Installation completed successfully and all functionalities work as expected, except from the FM radio.

Although I can find radio stations and listen to them, the audio has very poor quality (noise). The built in antenna/radio amp seem to work well, as I had no issues with my previous default bmw unit.
The Android head unit’s FM system seems to work well also, as when I disconnect the car antenna and attach a single wire the quality of audio is very good.

I know that a new antenna may solve the issue, but I want to make it work with the default antenna if possible.

Do you have any clue?
Thanks a lot for your time 🙏