[Mark VandeWettering] was experimenting with a simple transmitting circuit and an Arduino. The circuit in the project was designed by [Steve Weber] to broadcast temperature and telemetry data using Morse Code. But [Mark] wanted to step beyond that protocol and set out to write a sketch that broadcasts using the Hellschreiber protocol.
This protocol transmits glyph images, which are decoded as you see above. For some reason we can’t help but think this is like Captcha for radio enthusiasts. We have seen Hellschreiber used with AVR microcontrollers before, but this is the first Arduino implementation that we’ve come across. [Mark] does a great job of demonstrating his project in the video after the break. He mentions that the transmitter has no antenna, but is still being picked up by his receiving antenna mounted behind his house.
Since [Mark] doesn’t really cover the hardware he used, you will need to look back at [Steve's] original design schematics for more information.