Morning all.

My wife has a standard Arbath 500 which has a strange issue.

Turn on radio and listen to an FM station.
All good.

Plug in a USB charger to the 12v accessory connector
Still good

Plug in the TomTom 1005 Satnav and the FM fades in and out.

Unplug Satnav = all good
Plug in and it sounds like you are a long distance from the station antenna

Any pearls of wisdom as to why this happens and how to stop it?

Thanks

sounds like a crappy 12V to 5V converter, putting **** loads of noise around