First post on the forum. Not a huge deal, just a little curious. I bought my 2003 A4 about 2 months ago and included on the rear window was an external antenna. I know it's not factory, but was wondering if anyone had any insight. I'm guessing it's either for cellular amplification or radio signal amplification. It's definitely a passive device as there are no wires attached. It's fastened to the wnidow with adhesive and there are 2 components, 1 external and 1 internal. Figure it helps pass signals from inside the vehicle to outside and vise versa. Probably answered my own question but wanted to know if anyone has had any experience with these. Thanks!

Eric

 

It could be for an aftermarket alarm perhaps? GPS Satellite tracking? who did u buy the car from the Cia? make sure u always wear your seatbelt it can probably tell if you don't!!! lol

 

It does have this stamp on it "D.H.S."....

 

Those are aftermarket passive cellular antennas. I used to sell them all the time to people back when I sold cell phones