Outer Limits 4x4 Board

hey guys i have a mg 24v system bought it with a coverter in it already it only run a tape deck at the moment i want to put my uhf etc in now so i can get positive power from it but where do grounded it thank for any help

with down convertor you use the normal earth

Make sure it can supply enough current to power both radios if you are running them at the same time.