Coding Challenge: Signal Encoding/Decoding (CW, RTTY, PSK)

It would be cool, if you tried to implement signal encoders/decoders like Morse code, RTTY, PSK, FSK or even SSTV (for pictures) and some ham radio signals like THOR, THOB. You can ask the audience to decode messages you generate.
For a real world example, use websdr.org which is just a collection of the recievers from all over the world.