Recently the Raspberry Pi (Raspi) has gained much interest in the Ham Radio community. One interesting things is: the I/O pins provide access to a clock signal (GPCLK0) and it is possible to modulate this clock signal via software. This has motivated Guido Ten Dolle (PE1NZZ) to implement a WSPR transmitter and to publish the sources under GPL. Within the last days I have made some minor modifications to the WsprryPi sources, built a 30m QRP filter using the ugly method and connected everything to my doublet antenna.
Immediately my 10mW have been received in 743km distance by G6HUI (WSPR Spots) and within two weeks I was received in a distance of 7869km. Not too bad with about 10mW:
Information on how to do this yourself can be found in the WsprryPi repository.