Back in the mid 60's my dad replace the two motors in a control line scale twin with a couple of new 15 size diesels, after a few minutes of running them in our back garden to set them up, the old man that lived at the back of us was seen waving his stick and shouting at us. After my dad stopped the motors, the old man was swearing at us that the engines were interfering with his TV reception! He was told politely not to be so silly!
Better than that, I remember a time in about 1960, when my dad and I would go out very early in the morning to the local park, with rubber powered models to trim them in the still air. While getting a wakefield size model to fly around the park at about 7am, the local copper (policeman) stopped on his push bike to watch what was going on. Thinking he was interested, he summoned us over after the model landed, "has that got an engine in it"? he said in a very accusatory voice! My dad just said "did you hear anything then"? the copper gave us a dirty look and cycled off! Idiot.