WSPR (Weak Signal Propagation Reporter, pronounced "whisper") is a digital mode designed specifically for propagation research. It transmits highly compressed two-minute beacon signals at extremely low power, and a worldwide network of receivers automatically maps where those signals are heard. If you transmit WSPR from your station at 200mW on 20m, within minutes you'll have a map showing every country your signal reached. It's become the standard tool for antenna comparison, band monitoring, and ionospheric research in amateur radio.
What WSPR Actually Does
A WSPR transmission contains your callsign, your 4-character Maidenhead grid square, and your transmit power level — compressed into a 110-second transmission that occupies only 6 Hz of bandwidth. Receiving stations running WSPR decode signals down to -28 dB below the noise floor (weaker even than FT8), upload their decodes to WSPRnet.org, and the site plots them on a live world map. The entire system is automated — once configured, WSPR runs unattended, continuously mapping propagation while you do something else.
Software Setup: WSJT-X
WSPR is built into WSJT-X, the same software used for FT8. If you already have WSJT-X configured for FT8 operation, adding WSPR requires only:
- In WSJT-X, change Mode to WSPR
- Verify your callsign and grid square are entered correctly
- Set your transmit power level accurately (this is what gets reported to WSPRnet)
- Set the TX fraction — 20% (transmit 1 out of 5 two-minute windows) is standard for beacon use
- Enable Upload spots to WSPRnet checkbox
- Tune to the WSPR frequency for your target band (see table below)
Your computer clock must be accurate to within 1 second, same as for FT8. The system is fully automated once running — just minimize it and check the WSPRnet map periodically.
WSPR Frequencies
| Band | WSPR Dial Frequency (USB) | Activity Level |
|---|---|---|
| 630m | 0.4756 MHz | Low — Part 5 experimental |
| 160m | 1.8366 MHz | Active |
| 80m | 3.5686 MHz | Very active |
| 40m | 7.0386 MHz | Extremely active — best starting band |
| 30m | 10.1387 MHz | Very active — excellent for monitoring |
| 20m | 14.0956 MHz | Extremely active — best for DX mapping |
| 17m | 18.1046 MHz | Active |
| 15m | 21.0946 MHz | Active during solar max |
| 10m | 28.1246 MHz | Active when band is open |
| 6m | 50.2930 MHz | Active during Es season |
| 2m | 144.4890 MHz | Active for tropo monitoring |
Reading WSPRnet Maps
At wsprnet.org, the 2D map shows lines connecting transmitting and receiving stations. Each line color typically represents signal strength or SNR. Zoom in on your callsign to see exactly which stations heard you, at what signal level, and on which band. The database goes back years — you can query historical data to compare conditions on the same date across multiple years, or compare your antenna on a specific day by switching between two configurations and watching the pattern change.
Practical Uses for WSPR
Antenna comparison: The most common serious use. Connect Antenna A, run WSPR for 2 hours, then switch to Antenna B and run for another 2 hours. Download both datasets from WSPRnet, compare average SNR to the same receiving stations. The difference is a real measured gain/loss comparison between your antennas — far more meaningful than SWR measurements alone.
Band opening alerts: Run WSPR receive-only on multiple bands simultaneously using multiple receivers. When spots start appearing from distant regions on a quiet band like 10m or 6m, you know the band has opened — time to fire up the main transceiver and work some DX.
Propagation research: Run WSPR for weeks and map your station's propagation patterns across different seasons, times of day, and solar activity levels. The dataset you accumulate is genuinely useful for planning operating schedules and understanding your local RF environment.
QRP validation: WSPR at 100mW or even 10mW can still produce worldwide spots under good conditions, demonstrating just how capable a simple station can be for propagation work. Many QRP operators run WSPR as a continuous background activity to validate their station's reach.
Start here: Configure WSJT-X for WSPR on 20m (14.0956 MHz) at whatever power level your radio supports, set TX fraction to 20%, and let it run overnight. Check WSPRnet in the morning. You'll have a map of your signal's reach across multiple continents — and an immediate, visceral understanding of what HF propagation looks like at your location. It's one of the most educational experiments a new HF operator can run.
Running WSPR Receive-Only: The Passive Station
You don't need to transmit to benefit from WSPR. Running WSPR in receive-only mode — not transmitting, just decoding and uploading received signals — contributes to the global dataset and gives you a complete picture of what's arriving at your location on any band. This is valuable for operators in noise-prone environments who want to understand their receive environment, for those who want to participate without using transmit time, and for anyone running a dedicated monitoring station.
An RTL-SDR dongle with a good HF antenna can serve as a dedicated WSPR receiver feeding WSJT-X or the specialized WSPR software. Multiple bands can be monitored simultaneously with multiple receivers. This configuration — a dedicated WSPR receiver running 24/7 alongside your main station — provides continuous band-condition information without tying up your primary transceiver.
WSPR as a Foundation for Understanding Your Station
New operators often spend considerable effort and money chasing marginal performance improvements without a reliable way to measure the results. WSPR provides that measurement framework. Before buying a new antenna, run WSPR for two weeks on your current antenna and save the dataset. Install the new antenna and run WSPR for another two weeks under similar conditions. Compare median SNR to the same receiving stations. The difference is a real, measured comparison rather than speculation.
This methodology has led many operators to surprising conclusions: inexpensive wire antennas often perform within 3–6 dB of elaborate multi-element arrays on NVIS and regional paths; antenna height matters more than design on some bands; feedline loss at HF is often smaller than expected. WSPR makes these comparisons quantitative and reproducible in a way that pure on-air observations cannot. It's one of the most genuinely scientific tools available to the amateur radio community.
Recommended Tool
RTL-SDR Blog V4 — Dedicated WSPR Receive Station
Running WSPR receive-only on a dedicated RTL-SDR V4 leaves your main HF transceiver free for other operating. The V4's direct sampling mode covers HF bands natively, the stable TCXO keeps frequency accurate enough for WSPR decoding, and the whole setup costs under $50. Connect to a simple wire antenna and let WSJT-X upload spots 24/7 while your main station does other work.
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