I have been the worst operator - a 12v car battery with a large file brushed across the terminals :) That interfered with EVERYTHING. 25 years later, an EE de

I have been the worst operator - a 12v car battery with a large file brushed across the terminals :) That interfered with EVERYTHING. 25 years later, an EE degree and 5 years working RF comms engineering, I realise what an asshat thing to do that was.