What WSPR is
WSPR stands for Weak Signal Propagation Reporter, usually pronounced “whisper.” Joe Taylor (K1JT) created it as part of the WSJT software family. It is designed for sending very weak signals that can still be decoded, and for automatically reporting who heard whom. It is not a conversation mode. A WSPR station sends a short beacon and listening stations upload reports to a central database, so you learn where your signal was heard without needing a two-way contact.
How it works
Each WSPR transmission carries a small amount of information: a call sign, a four-character grid locator (related to your QTH) and a power level. The signal uses a very narrow bandwidth, only a few hertz wide, and a slow form of frequency-shift keying with strong error correction. Transmissions last a little under two minutes and begin at the start of even-numbered minutes, so your computer clock must be accurate. Stations either transmit in a given slot or listen, and many programs alternate automatically.
Because the signals are slow and narrow, they can often be decoded when they are far below the noise level heard by ear. Many people use very low transmit power, in the range of milliwatts to a few watts, and still appear on distant receivers when conditions allow.
What you need
- A receiver or transceiver that can operate in upper sideband on the band you choose. Receive-only setups work if you just want to report spots.
- A computer or small single-board computer running the software.
- A way to connect audio, either a sound interface, USB audio connection or a built-in digital interface on the radio.
- Software: WSJT-X is commonly used and includes WSPR. Some other programs and stand-alone beacon transmitters exist as well.
- Accurate time: use internet time or a GPS-based clock to keep your computer within about a second of true time.
- An antenna suited to the band. WSPR is a good way to compare antennas.
- A license if you plan to transmit.
Getting started in WSJT-X
- Install WSJT-X and enter your call sign and grid locator in the settings.
- Select your radio and audio input and output devices.
- Choose WSPR as the mode and pick a band. The software lists the standard dial frequency.
- Sync your computer clock.
- Listen first. After a few cycles you should see decodes with call signs, signal-to-noise values and distances.
- If you want to transmit, set a conservative power, enable the transmit percentage and check that your radio’s output is clean. Avoid driving the audio input too hard, which can create extra signals.
Reading spots and the map
Spots uploaded to the WSPRnet website include the sender, receiver, band, signal-to-noise ratio, power, and distance. A map and database lets you see which stations heard you and on which bands. Reports show propagation at the moment, not a guarantee of future conditions. Researchers and hobbyists use the data to study how the ionosphere changes over time, which also shapes HF radio range.
Typical frequencies
WSPR operates on narrow segments near the bottom of several bands. Typical dial frequencies include 7.0386 MHz on 40 meters, 10.1387 MHz on 30 meters, and 14.0956 MHz on 20 meters. Always verify frequencies against the current software list and your local band plan. More are listed in ham radio digital mode frequencies by band.
Tips and common problems
- No decodes: check the time, the audio levels and that you picked upper sideband.
- Wide or messy signal: reduce audio drive and turn off speech processing.
- Frequency drift: older radios may drift enough to move a signal out of the narrow passband. Allow the radio to warm up.
- Expectations: a single band is open to specific regions at a time. Try different bands at different times of day.
- Antenna tests: compare reports on the same band before and after a change. Use enough cycles to average out natural variation.
Related guides
If you are not sure whether you are seeing WSPR or a different weak-signal mode, see how to identify digital modes by sound and waterfall.