WSPR-zero is an open-source hardware and software project that turns a humble Raspberry Pi Zero into a powerful radio transmitter capable of sending WSPR signals across the globe. WSPR is a digital protocol that is used to research radio wave propagation around the world by bouncing off the ionosphere.

I first discovered WSPR while doing research for a future project on how to track a near-space balloon circumnavigating the earth.

The WSPR-zero board is based on the low pass filter by tapr,org but redesigned to comply with the design standards to fit on both the small footprint Pi Zero and the standard size Pi 3,4 and 5.

Version 2 of the board in currently in production and should be ready for beta testers in a couple of weeks!

The new board contains header pins for the Adafruit RTC if you are planning to test propagation on the road.

More info can be found on the WSPR-zero website and GitHub repo.