Android Auto .. (Chinese clones) FM reception

[anotherjohnv]

I have installed one of these in my 2018 VW Caddy, and the FM reception is too poor to be of any use. Some research would suggest that it's a known problem with these clones, and you can never get useable FM .. any one substantiate (or otherwise) this, before I splash out on an expensive powered aerial?
All the other functionality works very well .. I find it quite hard to believe that FM can't work.

I realise that the Caddy has an aerial in the wing mirror, I have an adaptor to make sure it's connected to the right one. I'm thinking that maybe the head unit does not power it .. in which case I'm happy to get a quality shark's fin installed to remedy this, but it's a bit of a gamble if it's a known issue.