WSPR Explained: Weak Signal Propagation Reporter for Beginners

The WSPR weak signal propagation reporter is a digital mode that turns your station into a tiny, automatic beacon. Pronounced “whisper”, it sends a short, slow transmission every few minutes at very low power, while other stations around the world decode it and upload the report to a shared map. Within an hour you can see which bands carried your signal, where it was heard and how strongly. You never speak to anyone, and nobody speaks to you. The point is information about the path.

For anyone curious about propagation, WSPR is one of the best learning tools in amateur radio. It also happens to be one of the best ways to compare antennas, test a new station and understand why a band opens on some days and not others. This guide explains how WSPR works, what you need to start, how to set it up in WSJT-X, how to read your results, and how it differs from modes such as FT8.

What WSPR Is and Where It Came From

WSPR is a protocol and a program that was designed by Joe Taylor, K1JT, and first released in 2008. As the overview of WSPR explains, it is intended for probing potential propagation paths on the LF, MF and HF bands with low-power transmissions. The protocol is now open source and is maintained as part of the same software family as WSJT-X, which also handles FT8 and several other weak-signal modes.

A WSPR transmission carries very little information: the transmitting station’s call sign, its four-character Maidenhead grid locator, and its transmit power expressed in dBm. A typical message looks like a call sign, a locator such as FN20 and a power figure such as 37, which corresponds to about 5 watts. That is all, because that is all that is needed to describe a propagation path: who sent it, from roughly where, and at what power. If you are not yet comfortable with locators, our guide to grid squares and the Maidenhead locator system explains how to find yours.

How a WSPR Transmission Works

WSPR is built to be as narrow and as slow as possible, because narrow and slow signals can be decoded far below the noise. The key properties are:

• Two-minute cycle. Transmissions start one second into an even UTC minute and last about 110.6 seconds.
• Four-tone frequency shift keying. The tones are separated by about 1.46 Hz, and the whole signal occupies roughly 6 Hz of bandwidth. That is narrower than a CW signal by a large margin.
• Heavy error correction. The 50-bit message is protected with a strong convolutional code, which lets the decoder recover the message even when parts are lost in noise.
• Very weak signal decoding. The decoder can recover signals at a signal-to-noise ratio of around -28 dB in a 2500 Hz reference bandwidth, which means the signal is far weaker than the noise you hear in your headphones.

Because every transmission is slow, a WSPR “contact” takes two minutes, and many stations are decoded in a single cycle. In a typical receive period a busy band can produce dozens of decodes, spread across a segment of about 200 Hz of audio spectrum. Each decode includes the call sign, locator, power, measured signal-to-noise ratio and frequency drift.

What You Need to Get Started

A WSPR station is simple. The minimum is a transceiver or receiver, a computer and an antenna. A good starter list looks like this:

1. A transceiver that can run upper sideband. WSPR uses the audio from the SSB mode, with an audio tone window in the 1400 to 1600 Hz range. Any HF transceiver capable of low power output is suitable.
2. A computer with an accurate clock. The sequences are timed to the UTC minute, so a clock that is off by more than a second or so will cause missed decodes. Our guide to FT8 time sync and computer clock accuracy applies to WSPR in exactly the same way.
3. An audio connection. This can be a USB audio interface built into the radio, or an external sound card interface. Keep the audio level low to avoid distortion.
4. An antenna. Almost any antenna will produce spots, and that is part of the appeal. A simple wire or vertical for a single band is enough to begin.
5. An internet connection. Receivers upload their decodes to a central database called WSPRnet, which publishes a map and a searchable table of spots.

Some operators use no transceiver at all. A small computer such as a Raspberry Pi and a few components can generate a WSPR signal, and a dedicated beacon module can run for months without attention. If you enjoy building, that is a very satisfying project, but it is optional.

Setting Up WSJT-X for WSPR

The WSJT-X user guide contains the official instructions. In outline, setup works like this:

1. Configure the basics. Enter your call sign and grid locator, select your audio devices and set up rig control or a push-to-talk method. This is the same set-up you would use for FT8, and our WSJT-X and FT8 setup guide walks through it step by step.
2. Select WSPR from the Mode menu. The main window reconfigures itself to the WSPR interface.
3. Choose an active WSPR frequency. The user guide gives 10.1387 MHz and 14.0956 MHz as examples. The Working Frequencies table in the program lists the conventional dial frequency for each band. For the 60 metre band, be sure to choose a frequency that is allowed under your local regulations.
4. Click Monitor to start a two-minute receiving period.
5. Enable uploads. In the settings, enter your WSPRnet credentials so that your reception reports reach the database.
6. Set your Tx percentage and power. If you want to transmit, choose a Tx percentage and a power level, then activate the Enable Tx button. Transmit periods are two minutes long and occur at random, to reduce the chance of clashing with other stations.

Set your transmit power to the level you intend to run and check it with a power meter. The WSPR power field is a statement, not a control, so if you tell the system you are sending 5 watts but run 50, the analysis of your signal will be wrong.

Choosing Power and Staying Legal

WSPR works at very low power. Many stations transmit with 200 milliwatts to 5 watts, and some use even less. Because the mode is designed to decode signals far below the noise, a few watts can often be heard across continents when conditions allow. Use the lowest power that gets you decoded; it keeps interference to a minimum and shows what your antenna can really do.

The transmission is an ordinary amateur signal, so your license conditions apply, including your permitted bands, power limits and identification rules. Each WSPR message includes your call sign, which satisfies the requirement for the transmission itself. Because WSPR runs for long periods and can transmit unattended, make sure that you are allowed to operate unattended or automatically controlled transmissions on the bands you choose.

Band Hopping

If your radio supports computer control, WSJT-X can hop between bands automatically. The program uses a repeating 20-minute schedule, in which each band is assigned to specific two-minute slots, so that a group of stations around the world moves from band to band together and increases the chance of finding an open path. You select the bands and times in the band hopping schedule window. An optional tune step sends an unmodulated carrier for a few seconds after a band change, which can trigger an automatic antenna tuner.

Band hopping is a useful way to survey a day of propagation without sitting at the radio. A day of hopping can show you when 40 metres opens to a particular region, when 20 metres carries your signal farthest, and when the upper bands wake up. For more background on why those changes happen, see our guide to what decides whether you are heard on HF.

Reading WSPRnet and Your Spots

When your signal is decoded, the receiving stations upload the report. The WSPRnet database lists the receiver’s call sign, the distance, the signal-to-noise ratio, your transmit power and the band. The map shows lines from your station to each receiver, and the table lets you filter by band, time and call sign. A few ways to read it:

• Look at the farthest spots. The most distant receiver on each band shows the best path of the moment.
• Compare signal-to-noise ratios. A higher figure on the same path means a stronger signal.
• Check the time of day. Plotting spots across 24 hours shows when each band opens and closes.
• Watch your own reception. A station that receives only, with no transmitter, still contributes useful data to the network.

It is easy to confuse WSPRnet with another reporting network. If you want to see who hears your FT8 or CW signals in real time, our guide to PSK Reporter covers that service. WSPRnet and PSK Reporter complement each other.

WSPR for Antenna Testing

One of the best uses of WSPR is comparing antennas. The method is simple: transmit from one antenna for a few hours, switch to another, and compare the reports. Because every report includes a measured signal-to-noise ratio, you get hard numbers instead of impressions. For a fair test:

1. Use the same power on both antennas. Do not change it between runs.
2. Run the tests at the same time of day. Propagation changes during the day, so compare similar periods, ideally on consecutive days.
3. Compare the same receiving stations. Spots from stations that heard both antennas are the only direct comparison.
4. Run for long enough. A few spots prove little. A few dozen on the same path begin to show a pattern.

This approach is particularly valuable for stations that run QRP. It shows how much a modest change, such as raising a wire or adding a choke, improves the real-world signal. Our introduction to QRP operating explains why low-power stations benefit so much from careful antenna work.

WSPR Compared With Other Weak-Signal Modes

WSPR belongs to the same family as FT8 and other WSJT-X modes, but it has a different job. The table summarises the differences between the most relevant modes.

FST4W is described in the WSJT-X documentation as a mode for sequences of two minutes up to 30 minutes, with sensitivity thresholds as low as -45 dB. It is an option once you have mastered WSPR, especially on the low bands. For a wider tour of digital modes, read our comparison of digital modes beyond FT8.

Common Problems and Fixes

• No decodes at all. Check that the dial frequency is correct, the radio is in USB mode, the audio level is sensible and the computer clock is accurate.
• Decodes but no uploads. Confirm that your internet connection works and that the upload option is enabled. Check your call sign in the settings.
• Your own spots look weak. Reduce audio drive, because overdriving the transmitter can create spurious signals and reduce the reported signal-to-noise ratio.
• Interference to other stations. Keep your Tx percentage reasonable and avoid transmitting for long periods on a crowded segment.
• Odd frequency drift reports. A drifting transmitter, whether a radio warming up or a poorly stabilised beacon, shows up in the drift figure of each spot.

The Bottom Line

The WSPR weak signal propagation reporter is a quiet, automatic mode that shows how your signal travels. It sends a short two-minute transmission at low power, other stations decode it far below the noise, and the reports appear on WSPRnet. You need a transceiver or a simple beacon, an accurate computer clock, an antenna and an internet connection. Use it to survey propagation, compare antennas and learn where your signal goes, and keep the power low and the settings honest. For anyone curious about HF, a few days of WSPR teach more than a month of casual listening.

Frequently Asked Questions

What does WSPR stand for?

WSPR stands for Weak Signal Propagation Reporter, pronounced “whisper”. It is a protocol and program by Joe Taylor, K1JT, designed to probe propagation paths with low-power transmissions.

Can I make contacts with WSPR?

No. WSPR is a one-way beacon mode. Stations send and receive reports, but there is no exchange of messages, so it does not produce normal contacts for logging or awards.

How much power do I need for WSPR?

Very little. Many stations run between 200 milliwatts and 5 watts. The message carries your power in dBm, and 37 dBm corresponds to about 5 watts.

Which software do I need?

WSJT-X includes a WSPR mode, along with FT8 and other modes. Other programs and small beacon hardware also exist, but WSJT-X is the usual starting point.

Why does my computer clock matter?

Transmissions start one second into an even UTC minute, and decoders expect that timing. If your clock is off by more than a second or so, you will miss decodes or be decoded poorly.

Where can I see my WSPR spots?

Receiving stations upload their reports to WSPRnet, which provides a map and a searchable table. You can filter by band, time and call sign to see who heard you and how strongly.