I am trying to finish my IV with a 582 and am getting a crackling sound during transmission at 4000 or more RPMs. No noise at lower RPM’s and if the engine is off. The radio is a used Val Com 760 TSO that came with the multiple boxes of parts when I bought the project. I tested the antenna and coax while engine is running using a handheld instead of my ratio and no issues. Last month I had a friend add some ferrites to the wires because prior to adding them the transmission was full of static and unrecognizable. The ferrites remove 98% of the static noise. At the suggestion of another forum member, we wired a .05 capacitor from the power wire to the ground wire that feeds the radio to remove the crackling sound at the higher RPM’s with no improvement. Any suggestions on getting rid of the crackling noise at higher RPM’s?

Thanks