It' s cold and raining outside, so for something to pass the time, I switch on my old shortwave radio, and turn the dial aimlessly.

In the same period China Radio International has almost doubled its short-wave output (see chart).

Though still able to cook food, its microwaves (essentially, short radiowaves) are modulated to encode information as though it were a normal radio transmitter.

It provides shortwave radios to schools and communities in some of the poorest areas of the world.

It also broadcasts a daily three-hour shortwave radio programme to North Korea with taped messages from relatives and news from the homeland.