Testing WSPR HF Propagation with a Raspberry Pi 3B+ and TAPR Shield Running WsprryPi
Thank you to Simone Spadino (SWL ID I8926BA), who wrote in to share his low-cost WSPR setup. WSPR (Weak Signal Propagation Reporter) is an amateur radio mode designed to test propagation paths using very low-power transmissions, with receiving stations reporting spots in real time to the WSPRnet map.
Simone's setup consists of a Raspberry Pi 3B+, which can be made to modulate a square wave RF signal on one of its GPIO pins via the WsprryPi software. Because a square wave generates many harmonics, he used the 20m WSPR shield from TAPR, which provides a low-pass filter to remove them. A dipole made from simple electrical monopole wire was connected to the shield via 50 ohm coax, and the signal was transmitted at 14.0971 MHz.
Transmitting from his rooftop in the center of Bari in southern Italy, Simone had his beacon received in England, Finland, Cyprus, and the Canary Islands, all more than 3100 km away. He repeated the experiment a week later with similar results. This is a reminder of how far low-cost hardware can transmit with a resilient protocol like WSPR.
Interesting experiment and impressive results for such low-cost hardware. However, one important point seems unclear: the article identifies Simone Spadino only with an SWL ID, and the WSPR map appears to show a non-standard identifier near Bari, not a regular Italian amateur radio callsign.
Since WSPR spots on 14.0971 MHz are the result of actual transmissions on the 20 m amateur band, this is not just a receiving/SWL activity. Could you clarify which licensed amateur radio callsign was used for the transmissions?
If the test was made under Simone’s valid amateur licence, a club station callsign, or another authorized station, it would be useful to mention that in the article. Otherwise, as currently written, it may look as if an SWL transmitted on amateur bands, which would be misleading and potentially problematic.