The GCARC WSPR Network is a club-wide collaborative project in which members build, deploy, and operate their own WSPR (Weak Signal Propagation Reporter) beacons from their home stations. Each member builds a low-cost, self-contained beacon using a TAPR Universal WSPR HAT kit and a Raspberry Pi Zero 2W. Once on the air, beacons transmit automatically 24/7, uploading propagation spot data to public databases that the entire club can then analyze together.

The project teaches Raspberry Pi and Linux skills, antenna design, RF kit-building, and data analysis — all in the context of real amateur radio experimentation. It is accessible to all license classes, generates meaningful propagation science, and grows in value the more members participate.

WSPR (pronounced “whisper”) stands for Weak Signal Propagation Reporter. It is a digital radio protocol developed by Nobel Prize laureate Joe Taylor, K1JT, specifically designed to probe ionospheric propagation paths using the minimum possible transmitter power.

Each WSPR transmission is exactly 110.6 seconds long and carries just three pieces of information — the operator’s callsign, 4-character Maidenhead grid square, and transmitter power in dBm. The encoded message is only 40.5 bytes, but it uses a sophisticated forward error-correcting code that allows receiving stations to decode signals 28 dB below the noise floor. This means a 200 mW WSPR beacon can reliably be heard across continents under the right ionospheric conditions.

The Pi Zero generates the WSPR signal entirely in software using its GPIO clock pin. The TAPR HAT amplifies this to 100–200 mW and passes it through a band-specific low-pass filter to suppress harmonics. No operator interaction is required — the system starts automatically on boot and transmits on a two-minute cycle.

There are thousands of WSPR receive stations around the world operating around the clock. Every decoded spot is uploaded in real time to public databases. The wspr.live database holds more than 4 billion spot records, all freely queryable via a public SQL API.

TAPR Universal WSPR HAT — tapr.org/product/wspr

The TAPR Universal WSPR HAT is the transmitter board for this project. Key specifications:

• Price: $32.00 per kit (member rate for W2MMD group purchase confirmed)
• Kit format: Surface-mount components pre-installed. User solders 4 inductors and 4 disc capacitors (through-hole only, no toroids)
• Output power: 100–200 mW (adjustable via on-board trimmer)
• Connector: BNC, located on the side opposite the Pi USB ports
• Available for all HF bands — each kit is band-specific
• Source: tapr.org/product/wspr — all bands confirmed in stock

Raspberry Pi Zero 2W with headers — Adafruit #6008 — $15

• Processor: Broadcom BCM2710A1 — quad-core 64-bit Arm Cortex-A53 at 1 GHz
• RAM: 512 MB LPDDR2 SDRAM
• Connectivity: 2.4 GHz Wi-Fi · Bluetooth 4.2 / BLE
• GPIO: 40-pin header pre-soldered — plugs directly onto the TAPR HAT
• Power: Micro-USB, 5V / 1A minimum (regulated supply required)
• Price: $15.00 (Adafruit #6008 — confirmed in stock)

The Pi Zero 2W runs Raspberry Pi OS (Debian Trixie) 64-bit Lite. Download using the Raspberry Pi Imager at raspberrypi.com/software. Select: Pi Zero 2W → Raspberry Pi OS (other) → Raspberry Pi OS Lite (64-bit, Trixie). Use the Imager’s customization to pre-configure Wi-Fi, SSH, hostname, and timezone. Club Tech Saturday sessions will pre-image SD cards — bring a blank 32 GB microSD.

The WSPR transmitter software is WsprryPi v2.x by Lee Bussy (AA0NT) — the official software recommended by TAPR.

• GitHub: github.com/lbussy/WsprryPi
• Documentation: wsprry-pi.readthedocs.io
• Installation: single-line curl script — compiles on-device, sets up auto-start as a systemd service
• Compile time on Pi Zero 2W: approximately 25–35 minutes (done once only)
• Configuration: via web browser at http://[hostname].local — no command line after install

Each TAPR HAT kit is band-specific. The best starting band is whichever HF band your existing antenna covers. If you have multiple antennas, choose the band that interests you most. If you have no existing HF antenna, 30m is an excellent starting point. Technician licensees must use 10m.

★ 30m is recommended if you have no existing HF antenna: WARC band (no contests), reliable 24/7 DX, largest global WSPR receive network.

✓ 10m is the required choice for Technician licensees. Digital modes permitted at 28 MHz. With current solar conditions, outstanding DX.

No dedicated antenna is required to start. WSPR transmits at 200 mW on a two-minute cycle and coexists peacefully with normal station operation. Connect the beacon’s BNC output to your existing HF feedline through a coax switch or T-connector, and flip to your main rig whenever you want to operate.

A simple half-wave wire dipole costs about $10 in materials and takes about 20 minutes to build. Wire lengths (each leg, from center insulator):

We will hold a series of Saturday sessions over the summer covering antenna design and construction for WSPR, including presentations on dipoles, inverted-V, end-fed half-wave, and random wire configurations, plus a hands-on antenna-building session. Coil-winding opportunities (EFHW matching transformers, common-mode chokes) will also be covered.

In addition to the transmit beacons, the club plans to build a dedicated receive-only station at the W2MMD clubhouse. A receive station needs no transmit license.

• Hardware: Raspberry Pi 4 or 3B+ + RTL-SDR V3 USB dongle (~$35)
• Software: rtlsdr-wsprd by VA2GKA — github.com/Guenael/rtlsdr-wsprd
• Important: Do NOT use the librtlsdr-dev package from apt — it has a known bug. Compile the osmocom rtl-sdr library from source.
• Multi-band: Run separate instances via cron to scan 30m, 20m, 40m, and 17m automatically

Any member can also build a home receive station for ~$50–60. No transmit license required to receive.

To find your own spots on wspr.rocks, navigate to the SQL tab and enter:

One of the most valuable aspects of the GCARC WSPR Network is the ability to pool all member station data and perform AI-assisted propagation analysis. Because wspr.live provides a public SQL API, automated queries can retrieve data and generate plain-language reports.

Types of analysis:

• Band performance comparison — spot counts and SNR by band and UTC hour
• Path analysis — which geographic regions are being reached from FM29
• Gray-line enhancement detection — DX distance spike at sunrise/sunset
• Antenna comparison — SNR delta between members at a common reference station
• Geomagnetic storm correlation — K-index vs. reporter dropout
• Member rankings — spot count, unique reporters, max distance, best SNR

AI resources will run scheduled queries to generate weekly summary reports automatically, posted to the Discord #wspr-project channel. Custom analysis can be requested at any time.

A dedicated beacon operating under the W2MMD callsign will be deployed at the club’s affiliated middle school, allowing students to watch their school’s radio signals propagate worldwide in real time on wspr.rocks. This connects directly to existing AI and prompt-engineering curriculum.

The 45-minute classroom lesson covers: radio waves and the electromagnetic spectrum, the ionosphere, the WSPR protocol, the Raspberry Pi as a radio transmitter, live map exploration, and career connections in RF engineering, atmospheric science, and data analysis.

NGSS connections: MS-PS4-2, MS-PS4-3, MS-ETS1

GCARC members are invited to visit the school and speak to students about the WSPR network and amateur radio, creating a pipeline to the next generation of operators.

1. Attend the April 1, 2026 General Membership Meeting for the full introduction and live demo
2. Sign up at the meeting (or contact WB2MNF) to reserve your kit in the group order
3. Order your Raspberry Pi Zero 2W with headers from Adafruit (#6008, $15)
4. Bring a blank 32 GB microSD card to the optional Build Day session
5. Attend the optional group soldering and software session — or assemble at home
6. Connect to your existing HF antenna and watch your signals appear on wspr.rocks

W2MMD  ·  Gloucester County Amateur Radio Club  ·  w2mmd.org  ·  Spring 2026