Hi Mike
You are most likely picking up harmonics (higher multiples of the sampling frequency) from the switch mode charger. I don’t think you can filter them out without losing broadcast frequencies so all I can suggest is that you move the aerial. Maybe try a stubby car aerial mounted under the side deck (or in a locker) some distance from the charger? This is what I have done on Playtime.
Before you take panels off etc., though, it would be worth moving the aerial around the saloon to check that position does make a difference.
It is also possible that the interference is coming through the power lead in which case you will need one of those ferrite toroids on the positive lead. This is less likely than aerial pick-up though.
Try moving the aerial first.
Good luck
Roger
