The WSPRLite SB from Sotabeams

The WSPRlite SB is a special test transmitter that sends a signal to a Worldwide network of receiving stations using WSPR. When used with the web-based DXplorer system, it’s a powerful new way to evaluate antenna performance. It comprises a low-power test transmitter used for probing potential propagation paths with low-power transmissions.

It sends a signal on your antenna out to a worldwide network of receiving stations listening in the WSPR mode. It carries a station’s callsign, Maidenhead grid locator, and transmitter power in dBm. It can decode signals with S/N as low as -28 dB in a 2500 Hz bandwidth.

Finally got around to exploring this cool little device – the WSPRLite SB from Sotabeams.

There is a Windows desktop app for configuring the WSPRlite transmitter available for download from the official DXplorer site. DXplorer is a web-based platform developed by SOTABEAMS that enables radio amateurs to monitor real-time propagation data and evaluate antenna performance using reports from the global WSPR network, particularly when paired with the WSPRlite low-power transmitter.

I highly recommend this tiny gadget!

My 0.2-watt signal reaches Australia from my QTH in Toronto

Going way beyond antenna modeling or antenna analyzers, this unique system allows you to see how your antenna is performing in its actual location and in real time! This type of analysis has never been possible before. WSPR or Weak Signal Propagation Reporter network is a group of amateur radio operators using K1JT’s MEPT_JT digital mode to probe radio frequency propagation conditions using very low power (QRP/QRPp) transmissions.

Watch my WSPRLite SB Demo

WSPR implements a protocol designed for probing potential propagation paths with low-power transmissions. Transmissions carry a station’s callsign, Maidenhead grid locator, and transmitter power in dBm. The program can decode signals with S/N as low as -28 dB in a 2500 Hz bandwidth. Stations with internet access can automatically upload their reception reports to a central database called WSPRnet, which includes a mapping facility. It’s extremely cool.

A Beginner’s Guide to Using a WsprLite

If you’re excited about the real-world propagation magic demonstrated in the WSPRLite SB demo above, you’re in the right place. WSPR (Weak Signal Propagation Reporter) is a game-changing digital mode for amateur radio enthusiasts, allowing you to transmit ultra-low-power signals (as low as milliwatts) and track their global journey via a worldwide network of receivers. Paired with the compact WsprLite device, it becomes an effortless tool for antenna testing, propagation forecasting, and even QRP adventures. In this section, we’ll walk through the essentials of WSPR, a simple setup guide for your WSPRlite, and tips to maximize your spots on WSPRnet.org. Whether you’re new to WSPR or looking to optimize your WSPR Lite setup, this guide will help you get transmitting in under 30 minutes.

What is WSPR and Why Use It with WSPRlite?

WSPR, developed by Nobel laureate Dr. Joe Taylor (K1JT), is more than just a mode—it’s a collaborative global experiment in weak-signal communication. Transmissions are short (under 2 minutes), encoded with your callsign, Maidenhead grid square, and transmit power in dBm, and can be decoded at signal-to-noise ratios as low as -28 dB. Unlike traditional CW or SSB, WSPR focuses on reporting propagation paths rather than two-way QSOs, making it perfect for:

• Antenna Performance Testing: Compare end-fed wires, dipoles, or verticals in real conditions—no more relying solely on SWR meters.
• Propagation Prediction: Spot openings to Europe from North America before they hit the 20m DX window.
• QRP Fun: Push 200mW signals across oceans, as seen in the Toronto-to-Australia demo earlier.

The WsprLite shines here as a standalone, GPS-disciplined beacon. No computer needed after initial setup—it syncs time automatically and beacons on multiple HF bands (160m to 10m). It’s battery-friendly, portable for SOTA/POTA activations, and integrates seamlessly with DXplorer.net for live mapping.

Specifications

• Standard message: callsign + 4-digit locator + dBm
  (e.g., K1ABC FN20 37)
• Messages with a compound callsign and/or 6-digit locator:
  Use a two-transmission sequence.
• The first transmission carries the compound callsign and power level, or standard callsign + 4-digit locator + power level.
• The second transmission carries a hashed callsign + 6-digit locator + power level.
• Add-on prefixes: up to three alphanumeric characters.
• Add-on suffixes: a single letter or one or two digits.

Standard message components (after lossless compression):

• 28 bits for callsign
• 15 bits for locator
• 7 bits for power level
• Total: 50 bits

Forward Error Correction (FEC)

• Non-recursive convolutional code
• Constraint length K = 32
• Rate r = 1/2

Transmission Parameters

• Number of binary channel symbols:
  nsym = (50 + K - 1) * 2 = 162
• Keying rate: 12000 / 8192 = 1.4648 baud
• Modulation: Continuous phase 4-FSK
  Tone separation: 1.4648 Hz
• Occupied bandwidth: about 6 Hz
• Synchronization: 162-bit pseudo-random sync vector
• Data structure: Each channel symbol conveys:
• 1 sync bit (LSB)
• 1 data bit (MSB)
• Duration of transmission:
  162 * 8192 / 12000 = 110.6 seconds
• Transmission timing: Nominally starts one second into an even UTC minute
  (e.g., at hh:00:01, hh:02:01, etc.)
• Minimum S/N for reception: around –28 dB on the WSJT scale (2500 Hz reference bandwidth)

Step-by-Step WSPRLite Setup Guide

Setting up your WsprLite is straightforward. You’ll need a computer (Windows/Mac/Linux) or Android device, a USB cable, and an internet connection for the config app. Download everything from the official DXplorer.net site (linked in your WsprLite docs).

1. Install Drivers and Software:

• Head to DXplorer.net/wsprlite and download the WsprLite Configuration App.
• For Windows, install the FTDI USB drivers (included in the app package). Mac/Linux users may need to grant USB permissions.
• Pro Tip: If drivers don’t auto-install, manually download from FTDI’s site and restart your computer.

1. Connect and Configure:

• Plug your WsprLite into USB (it draws power from the port—no external supply needed yet).
• Open the config app, select the correct COM port (check Device Manager on Windows), and click “Connect.”
• Enter your details:
  • Callsign: Your amateur radio callsign (e.g., VE3XYZ).
  • Grid Square: Your Maidenhead locator (find it at gridmapper.free.fr).
  • Transmit Power: Start with 10-14 dBm (about 25-50mW) for testing; max is 20 dBm (100mW).
  • Bands: Select 1-4 frequencies (e.g., 20m: 14.0956 MHz, 40m: 7.0400 MHz). WsprLite cycles through them.
  • Mode: Standard WSPR (not WSPR-X for now).
• Hit “Write Config” and “Disconnect.” Unplug and reconnect to verify settings via the app’s “Read Config.”

1. Antenna and Power Up:

• Connect a tuned antenna (e.g., 20m half-wave) to the BNC output. Use an external low-pass filter if needed to stay clean.
• Power via USB (5V, 100mA) from a wall wart, battery pack, or even solar for field ops.
• Press the “Sync” button once to calibrate GPS time— the LED blinks green when ready.
• It starts transmitting immediately: 1-minute tone, 1-minute off, repeating every 2 minutes.

1. Verify on WSPRnet:

• Wait 10-15 minutes, then visit wsprnet.org.
• Search for your callsign under “Advanced > Waterfall.” Spots should appear as green dots on the map.
• No spots? Check antenna SWR (<2:1 ideal) or move to a higher band during grayline.

Common Pitfall: If the app won’t connect, ensure no other software (like WSJT-X) is hogging the COM port. Update firmware via the app for the latest stability fixes.

Tips for Better WSPR Performance with WSPRLite

• Timing is Everything: I left mine running for a full month unattended.
• Antenna Tweaks: My End-fed half-wave vertical with a 9:1 unun is what I use for maximum DX.
• Low-Noise Setup: I use an ugly balun in my shack to terminate the counterpoise and any shack RF.
• Alternatives to WsprLite: Compare to the QRP Labs U3S kit (DIY, $60) or Pi-based beacons—WsprLite wins for plug-and-play portability.

Monitoring Your WSPR Spots on WSPRnet and DXplorer

WSPRnet.org is the heartbeat of the WSPR community—a free database where thousands of stations upload spots in real-time. Here’s how to make it work for you:

• Basic Map View: Go to wsprnet.org, select “Waterfall” or “Map,” filter by band/time/your callsign. Zoom to see paths—your 0.2W signal hitting VK? Screenshot it for bragging rights!
• Advanced Filtering: Under “Advanced,” set min/max distance, S/N threshold (-25 dB+ for reliability), or exclude noisy spots. Export data as CSV for analysis in Excel.
• DXplorer Integration: For WsprLite-specific magic, log into dxplorer.net with your callsign. It auto-pulls your spots, overlays propagation forecasts, and even alerts for new DX. Link your WsprLite by entering its serial number in the config app.

Pro Tip: Upload spots promptly—WSPRnet refreshes every 5 minutes. Join the WSJT-X reflector for community help.

FAQs: Common WSPR and WsprLite Questions

• What’s the difference between WSPR and FT8? WSPR is receive-only reporting for propagation; FT8 is for QSOs. Use WSPR to scout bands before FT8 hunting.
• Can WsprLite transmit on VHF/UHF? The classic model is HF-only (1.8-28 MHz), but check for the 2m/70cm variants.
• How accurate is the GPS timing? Spot-on to within 1 second—essential for WSPR’s narrow 6Hz tones.
• Legal to use? Yes, on amateur bands with your license. Keep power under ERP limits (e.g., 5W on 20m).
• Battery Life? 24+ hours on a 2000mAh LiPo; it sips just 25mA TX.

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