Eddie G3ZJO used the 10 mW of RF that can be generated from the Raspberry Pi computer board to get over 2000 km on the 7 MHz band.
The Raspberry Pi board can operate as a WSPR transmitter covering LF, HF and VHF up to 250 MHz.
Eddie G3ZJO connected the board's GPIO port via a low pass filter to a 40m Doublet for the 7 and 14 MHz bands or to a small Marconi inverted L just 6m up 6m out for the 472 kHz band which he estimates generates an ERP of 0.5 microwatts.
Among the stations who received his WSPR signal were:
- LA9JO JP99gb 2124km on 7MHz
- LY2BOS KO24or 1736km on 14MHz
- IK1WVQ JN44cb 1133km on 7MHz
- G4KPX JO02dj 80km on 472kHz
- G3XIZ IO92ub 46km on 472kHz
The PE1NNZ code and binary to turn the Raspberry Pi into a WSPR LF/MF/HF/VHF transmitter is available at https://github.com/threeme3/WsprryPi