Aerial in bootlid - how to test if it/they are working

[gsmdo]

Whilst I was fitting a new head unit and reversing camera into my 2006 A4 B7 convertible, I noticed these two modules in the boot lid:

Which, on closer inspection...

 

...seem to be the 'hidden' radio antennae.

The radio has always had bad reception. Since I almost never use it, this hasn't really been a problem.

Except I'm half-German, and I can hear my Mother admonishing me from beyond the grave to get it tested and fixed... 😆

Does anyone know of a method of testing these units to try to track the problem down, please?

Thanks,

Mike😎