What do you get when you mix a cheap MSP430 development board with a simple oscillator circuit and blend in a handful of code from various sources? Hellschreiber– a radio transmission mode invented in the 1920s.

MSP430 Launchpad and Oscillator

The screenshot above shows the signal as transmitted across my bench – a distance of about 50cm. The text being transmitted is “G7UVW / QTH / JO01BN / QRPP / Hellschreiber”. The slanting of the text is due to the drift in frequency between the transmitter and receiving radio and also timing errors in the transmitting code.