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Applications
Raspberry Pi as WSPR transmitter
The protocol was designed to test propagation paths on the LF, MF and HF bands. Also used experimentally at VHF and higher frequencies. Other applications include antenna testing, frequency stability and frequency accuracy checking. Usually a WSPR station contains a computer and a transceiver, but it is also possible to build very simple beacon transmitters with little effort. For example a simple WSPR beacon can be built using the Si 570,[5] or Si 5351.[6] The Raspberry Pi can also be used as WSPR beacon. Density distribution of WSPR spots, January 2014 vs July 2014, using only most distant reception per spot.
Note - an accurate clock is essential both for transmission, and decoding of received signals (native Windows timing is usually inadequate).
MH370
In May 2021, aerospace engineer Richard Godfrey suggested
an examination of historical WSPR data to further define the flight path of Malaysian Airlines flight MH370 on 8 March 2014, suggesting that there were "518 unique transmission paths that cross the area of interest around Malaysia, the Malacca Strait and the Indian Ocean. With the WSPR data provided every two minutes and the ability to check against the satellite data every hour it is possible to detect and track MH370 from two independent sources."[7]
However, the method used in this article is highly questionable; The reflected signal energy from aircraft in such distances is very small (inverse square law), much smaller than variance on the regular skywave signal due to multipath propagation, which can vary by tens of dB within seconds. Such difficulties make it necessary to use more advanced methods for radar applications at such distances in this frequency range (Over-the-horizon radar). But, the theory is sound. Better data may provide new insights especially if it agrees with prior techniques utilized which have already defined a general search area.