Weak Signal Propagation Reporter (WSPR).
Used for weak-signal radio communication between amateur radio operators.
Designed for sending and receiving low-power transmissions to test propagation paths on the MF and HF bands.
WSPR implements a protocol designed for probing potential propagation paths with low-power transmissions.
Transmissions carry a station’s callsign, Maidenhead grid locator, and transmitter power in dBm.
Stations with internet access can automatically upload their reception reports to a central database called WSPRnet, which includes a mapping facility.
You will need:
•PiFM with a wrapper
•A low pass filter
•0 to 250MHz