WSPR

WSPR stands for Weak Signal Propagation Reporter. It is a digital communication mode that allows radio operators to transmit minimal data packets across continent-spanning distances using just a few watts of power, then automatically logs reception reports from other stations. The mode encodes a station's callsign, grid square location, and transmit power into a 162-second transmission frame that repeats every 10 minutes, creating a real-time map of ionospheric propagation conditions worldwide.

The protocol was developed by Joe Taylor, K1JT, and released in 2008 as part of the WSJT software suite. WSPR transmissions occupy only 200 Hz of bandwidth and use frequency-shift keying at 1.46 baud, making them detectable even when signal strength falls 10 to 15 decibels below the noise floor. The mode tolerates poor frequency stability and clock accuracy far better than earlier weak-signal modes, which is why it has become the standard for antenna tuning, propagation research, and distance testing with QRP (low-power) equipment.

Common use and hardware

Operators typically run WSPR on amateur radio bands between 160 meters and 70 centimeters, most commonly on 20 meters (14.097 MHz) where the propagation is most predictable. A typical WSPR station needs only a computer running WSJT-X software, a transceiver capable of frequency stability within 2 ppm, and an antenna. Many operators use simple dipoles or long wires; others test directional arrays. The transmitted power ranges from less than 100 milliwatts on VHF to several watts on HF bands.

Because WSPR spots are automatically uploaded to a central database maintained at wsprnet.org, operators worldwide accumulate propagation statistics across years of continuous operation. This creates a permanent record of how the ionosphere responds to solar activity, geomagnetic storms, and diurnal cycles. Radio clubs and manufacturers use WSPR to validate antenna designs and measure equipment performance under real-world conditions without needing to coordinate with other operators.

WSPR differs from traditional CW or SSB weak-signal work in that it requires no human at the radio to decode incoming transmissions; the software identifies transmissions probabilistically even when they are completely inaudible. This automation means a station can run unattended for days, accumulating dozens or hundreds of reception reports. The tradeoff is that WSPR carries no message content, only identification and power level, so it serves propagation measurement rather than actual communication.