Flipping through the frequencies and the different wave lengths was one of my favourite things to do as a kid. You are meant to be asleep, but you’ve got the transistor radio and a single ear phone plugged in.
I use to love getting the foreign stations and listening to the different languages, music styles and jingles. It was exotic and strange simultaneously.
I’ve been researching around some parts of spy craft for my Science Fiction writing and I came across the collection of recordings from Number Stations at the Internet Archive:
They are a perfect anonymous one way communication method that have probably been in use since the First World War. Government intelligence agencies have a very simple but effective way of letting their agents in the field know something.
They don’t need any really special equipment and the code is practically unbreakable as it will need a one use pad to decrypt it. For the country that has a spy infestation, it is almost impossible to track down these message recipients once they are embedded.
A simple and very powerful system.
More info: http://en.wikipedia.org/wiki/Numbers_station