Does rust really affect an antenna? Most would say "no, it still works." Yes, it does work, but that's not the point. Does rust affect the quality of the reception? On an old car, how do we know when an antenna need to be replaced? What if the thread holding the antenna on is rusted too? Again, yes, it works.

So can audio experts offer an official answer?

 

Most FM antenna's are usually coated with zinc to prevent rust. Small amounts will have little to no effect on reception. You can't really say for sure how much of an effect a certain amt of rust will cause on an antenna with out doing signal strength tests. If you have an older antenna with rust on it all you have to do is take a wire brush to it and clean it off. If is rusted badly and you cannot get rid of it all with a wire brush then it's probably time for a new antenna. Rust in between the threaded stud and the threaded socket will have much greater effect on signal loss as it creates a resistance barrier between the antenna itself and the cable going to your receiver.