So one slightly fascinating bit of number station / espionage radio lore is "RAFTER" an MI5 scheme cooked up by Peter Wright to detect the _receiver_ of the rad

So one slightly fascinating bit of number station / espionage radio lore is "RAFTER" an MI5 scheme cooked up by Peter Wright to detect the _receiver_ of the radio using emissions from the internals of the radio set (superhet mixing iirc) https://en.wikipedia.org/wiki/Operation_RAFTER https://en.wikipedia.org/wiki/Operation_RAFTER