WSPR is amazing!  A tiny and inexpensive transmitter sends low speed morse code that can be heard around the world.

$29 WSPR transmitter kit from http://www.qrp-labs.com/

What is WSPR?

WSPR stands for Weak Signal Propagation Reporter, but it’s pronounced “Whisper” – quite an appropriate name as it is all about sending and receiving signals that are barely audible.

WSPR is a software application written by Joe Taylor, K1JT, a Nobel Prize-winning Princeton physicist. It was first released in April 2008. It uses a transmission mode called MEPT-JT. The “JT” stands for Joe Taylor, while MEPT stands for Manned Experimental Propagation Transmitter.

MEPT is not something specific to WSPR. MEPTs are very often simple home-built QRP transmitters that send beacon messages using very low-speed Morse (QRSS). Their very weak signals are copied visually using software called a “grabber” – a horizontal waterfall display capable of detecting and highlighting signals well below the noise threshold. The content of a transmission is determined – as with many other weak-signal QRSS modes such as EME (moonbounce) – by literally reading the dots and dashes as they are displayed on the waterfall.

The “manned” aspect of MEPT simply relates to the operator’s license conditions. It is not necessary to obtain a special dispensation to operate a MEPT station because you are present while it is in use, just as you would be when using CW, SSB or another data mode. In fact, some MEPT enthusiasts discourage the use of the term “beacon” because beacon operation without a special permit is prohibited by some licensing authorities.

http://www.g4ilo.com/wspr.html

Pi and Ham – Yes you can!

https://github.com/threeme3/WsprryPi