Tiny, cheap and precise WSPR gear brought to you by OK1RAJ DevTeam

The openWSPR modules are open-source tools capable of transmitting and receiving WSPR signals in the shortwave band.

The WSPR network is made up of thousands of individual (mostly amateur operated) receivers scattered all over the world, with a single purpose - to relay received messages into an online database. This data can be used to scan current signal propagation or to analyze your anntenae.

The WSPR network

WSPR signals in spectrogram view

'WSPR (pronounced "whisper") stands for "Weak Signal Propagation Reporter". It is a protocol, implemented in a computer program, used for weak-signal radio communication between amateur radio operators. The protocol was designed, and a program written initially, by Joe Taylor, K1JT. Software is now open source and is developed by a small team. The program is designed for sending and receiving low-power transmissions to test propagation paths on the MF and HF bands.

Spot vizualization map on

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. The program can decode signals with S/N as low as −34 dB in a 2500 Hz bandwidth. Stations with internet access can automatically upload their reception reports to a central database called WSPRnet, which includes a mapping facility.'

source: Wikipedia

WSPR details

Wikipedia WSPRnet

Spot visualization