ABOUT THE PROJECT
Q: What is WSPR and why are we using it?
WSPR (Weak Signal Propagation Reporter, pronounced “whisper”) is a digital radio beacon protocol designed specifically to probe HF propagation paths at the lowest possible power levels. Each beacon transmits a short, highly efficient burst every two minutes carrying just your callsign, grid square, and power level. Receiving stations worldwide decode those transmissions — even when the signal is far below the noise floor — and upload the results to a global public database. Within minutes of transmitting, you can open a browser and see exactly which stations heard you, on a world map, in real time.
We are building the GCARC WSPR Network because every member station that participates adds to a shared pool of propagation data. One beacon is a novelty. A dozen beacons spread across the club’s service area, all feeding the same database, becomes a genuine scientific instrument. We can compare antennas objectively, track how bands open and close through the solar cycle, identify gray-line enhancement, and generate AI-assisted analysis reports — all automatically, while our beacons run unattended 24/7.
Q: Is this a transmitting mode or a receiving mode, or both?
It is both, but the two functions operate independently. The TAPR HAT kit we are building is a transmitter. Once configured, it broadcasts your beacon signal automatically every two minutes and relies on the global network of other operators’ receive stations to hear it and log the spots. You contribute data to the world simply by having your beacon on the air.
Separately, the club plans to build a dedicated receive-only station at the W2MMD clubhouse using a Raspberry Pi and an inexpensive RTL-SDR V3 USB dongle. Individual members can also build their own home receive stations — no transmit license is required to receive — for about $50 in hardware.
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HARDWARE AND COST
Q: What if I already have a Raspberry Pi — can I use it?
Possibly. The WsprryPi software that drives the TAPR HAT is compatible with the Pi Zero 2W, Pi 3, and Pi 4. It is NOT compatible with the Pi 5, which uses a different peripheral architecture. If you have one of the supported models running a 64-bit Raspberry Pi OS (Trixie), you are likely good to go.
The one catch is that WsprryPi disables the Pi’s onboard audio output, because it uses the same PWM hardware to generate the RF signal. For most members, a $15 Pi Zero 2W is the cleanest solution.
Q: Is there an ongoing cost?
Almost none. The wspr.live and wspr.rocks databases are completely free — no account, no subscription, no API key required. The WsprryPi software is free and open source. There are no fees of any kind associated with participating in the WSPR network.
The only ongoing cost is electricity. A Pi Zero 2W draws about 1–2 watts under load. Running continuously, that is roughly 15–17 kWh per year — about $2 to $3 on a typical utility bill. The beacon costs less per year to run than a cup of coffee.
Q: Can I buy it pre-assembled, or do I have to build it myself?
You build it yourself, and it is straightforward. The TAPR Universal WSPR HAT arrives with all surface-mount components already installed at the factory. Your job is to solder exactly eight through-hole parts into their marked positions: four small inductors and four disc capacitors that form the low-pass filter for your chosen band. No surface-mount work, no fine-pitch ICs, no toroids. After soldering, you set the bias current with a multimeter and configure the software through a web browser. That’s the entire build.
We will hold a dedicated Saturday work session where experienced members will be on hand to assist with soldering, bias setting, and software setup. Most hams with any kit-building experience will be comfortable doing this on their own at home.
Q: How complicated is the build?
On a scale of 1 to 5, we would rate this a 2. The soldering consists of eight through-hole components in clearly marked positions — four inductors and four disc capacitors. The pads are generously sized and the board is well-documented. Most people finish the soldering in 20–30 minutes. After that, you set the bias current with a multimeter, which takes another five minutes.
The software side is equally simple. WsprryPi installs with a single copy-paste command, compiles automatically on the Pi (about 30 minutes on the Zero 2W — walk away and let it run), and is configured entirely through a web browser. Enter your callsign, grid square, and band, click Save, and the beacon is on the air. No Linux knowledge required.
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ANTENNAS AND STATION INTEGRATION
Q: My HOA won’t allow outside antennas — can I still participate?
Quite possibly. WSPR is remarkably forgiving of compromise antennas because the decoding threshold is so far below the noise floor. Members have reported successful coast-to-coast spots running a few feet of wire along a window frame, a magnetic loop indoors, or even a wire run along a baseboard. At 200 mW with a receive network as sensitive as WSPR’s, even a poor antenna will produce spots under reasonable band conditions.
If your situation is truly antenna-constrained, consider building a receive-only station instead. Receiving requires no outside antenna and no transmit license. Talk to WB2MNF about options specific to your situation.
Q: Will the beacon interfere with my regular rig when I want to operate?
No — with a small amount of planning. The TAPR HAT transmits on every two-minute cycle and occupies only 6 Hz of spectrum. The simplest approach is to share your existing HF antenna: connect the beacon’s BNC output to your feedline through a coax switch or T-connector, and flip the switch to your main rig whenever you want to operate normally.
If you want to use the same antenna on the same band your beacon is on, simply flip the coax switch. The beacon will keep its timing cycle, but without an antenna connected it will not transmit. There is no damage to the board from a brief open-circuit condition at 200 mW.
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BAND SELECTION
Q: Which band should I start with?
The best starting point is whichever band your existing antenna already covers. If you have a 40m dipole, start there. If you have a multiband vertical, pick the band that interests you most for propagation research. There is no wrong answer — every band produces useful data and every member station strengthens the club network.
If you have multiple HF antennas, choose the band that interests you most. If you don’t have an existing HF antenna, 30 meters is an excellent choice: it is a WARC band (no contests, ever), propagation is reliable around the clock, and the 30m WSPR receive network is the most active of any HF band. Technician licensees must use 10 meters — digital privileges apply there, and with the current solar cycle it is producing outstanding DX. We will also be holding antenna presentations and a hands-on antenna-building session on Saturdays over the summer covering the most popular WSPR antenna designs.
Q: I only have a Technician license — can I participate?
Yes — 10 meters is your band. Technician licensees in the US have full HF digital privileges at 28 MHz, and WSPR is classified as a digital mode. We are near the peak of Solar Cycle 25 right now, and 10m is regularly producing exceptional DX propagation. A 10m WSPR beacon will generate some of the most exciting spots in the club network when the band is open.
The 10m antenna is also the smallest of any HF WSPR option — a half-wave dipole is only about 17 feet total, making it workable even in tight spaces. The TAPR 10m kit is the same $32 as any other band.
Q: Can I run on multiple bands at once?
Each TAPR HAT is built for one band — the low-pass filter components you solder determine the operating band. To run multiple bands simultaneously, you would need multiple HAT and Pi combinations, one per band. There is no technical reason you can’t run two beacons — say, one on 30m and one on 10m — each on its own Pi Zero 2W. At $73 total per station, running two bands costs about $146.
We recommend starting with a single-band setup and expanding later once you are comfortable with the system.
Q: Why is 30m recommended over 20m if 20m has more DX?
20m has more DX potential during peak daytime hours, but it essentially shuts down at night when the F-layer thins out. A 20m beacon produces interesting data for perhaps 8–10 hours a day and very little the rest of the time. 30m, by contrast, stays open around the clock — supporting NVIS propagation during the day and longer-path DX at night. For a beacon meant to run 24/7, 30m is more productive over a full 24-hour cycle.
The other factor is the receive network. 30m has the largest concentration of active WSPR receive stations worldwide. More listeners means more spots per transmission and richer data for analysis. 20m makes a great second band once you have 30m running.
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SOFTWARE AND OPERATION
Q: Does it need to be connected to the internet?
Yes, for two reasons. First, the Pi synchronizes its clock via NTP over the internet. WSPR transmissions must begin precisely at the start of each two-minute UTC boundary — if the clock drifts by more than about one second, decoded spots drop off. A Pi on a reliable home Wi-Fi network stays accurate to within milliseconds of UTC, far better than required.
Second, the WsprryPi software uploads your spot data to wspr.live automatically after each transmission. Without internet, your beacon will still transmit and the global network may still hear you, but you won’t see your own spots in the database and your data won’t contribute to the club’s analysis. The beacon uses only a few kilobytes of data per day.
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READING YOUR DATA
Q: What does a typical day of spots look like?
On 30m with a modest antenna, a typical day might produce 80–150 individual spot records spread across 20–40 unique receiving stations. During the day you will typically see regional spots from stations within 500–1,500 miles. After sunset, longer paths open up and it is entirely normal to be heard in Europe (4,000–5,000 miles) or even Japan (7,000+ miles) overnight. When the band is really performing, a single 200 mW transmission can be logged by 50 or more stations simultaneously.
You can explore all of this on wspr.rocks in real time. Navigate to the SQL tab and query your callsign to see every spot with timestamp, receiving station, SNR, distance, and frequency. The map view shows all active propagation paths on a world map, updated every two minutes.
Q: How do I interpret the SNR numbers I see in the database?
SNR (Signal-to-Noise Ratio) is reported in dB, referenced to a 2,500 Hz noise bandwidth. Zero dB means your signal equals the noise in that bandwidth. Positive values (e.g., +5 dB) mean the signal is above the noise — easily audible. Negative values are normal for WSPR: -10 dB means your signal is 10 dB below the noise, -20 dB means 20 dB below. The protocol reliably decodes signals as weak as -28 dB — far below anything a human ear or conventional waterfall display would detect.
For antenna comparison, SNR is the key metric. When your beacon and another club member’s beacon are decoded by the same receive station at the same time, the difference in your SNR readings is a direct, objective measurement of the difference between your two antenna systems in dB. No field strength meter, no guesswork.
Q: What does “drift” mean in the spot data?
Drift is the rate at which your transmitter’s frequency is shifting during the 110-second transmission, reported in Hz per minute. Ideally it should be zero or very close to it. A value of ±1 Hz/min is fine. Values larger than ±2–3 Hz/min begin to cause missed decodes at marginal signal levels.
Common causes are thermal instability (the Pi warming up, or a beacon in direct sunlight) and power supply noise. If you see high drift in your spot data, try moving the Pi to a cooler location or using a better-regulated power supply. WsprryPi also has a PPM correction setting to compensate for a systematic frequency offset.
Q: Can other club members see my spots, and can I see theirs?
Yes — all spot data is completely public. Every spot from every WSPR station in the world is visible to anyone who visits wspr.rocks or wspr.live. You can search by any callsign, any band, any date range. There is no private mode in WSPR — the whole point is shared, open data.
For the club project, AI resources will run regular automated queries across all W2MMD member callsigns to generate club-wide analysis and comparison reports. Reports will be shared through the Discord #wspr-project channel and presented at club meetings.
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THE CLUB NETWORK
Q: What kind of propagation data will we actually collect?
The club network will generate a continuously updated picture of HF propagation as seen from the FM29 grid area (Mullica Hill, NJ and surroundings): which bands are open at which times of day, how far each band reaches in each direction, how conditions change through the seasons and the solar cycle, how geomagnetic storms affect different frequencies, and how the gray-line creates brief windows of exceptional DX on the lower HF bands.
Beyond propagation, the data becomes a precise antenna testing tool. When two club members transmit on the same band and are heard by the same receive station, the SNR difference between them is a direct measurement of their antenna performance difference in dB. This lets us compare dipoles vs. verticals, different heights, different orientations, and different matching approaches in a scientifically rigorous and completely objective way.
Q: Will I get regular reports automatically, or do I have to request them?
Both. AI resources will run scheduled queries against wspr.live and generate weekly summary reports automatically, covering things like best DX of the week, band performance trends, and member station comparisons. Reports will be posted to the Discord #wspr-project channel automatically.
You can also query your own data any time at wspr.rocks — no account needed, just enter your callsign. For custom analysis — comparing your antenna before and after a change, or reviewing propagation during a specific event — drop a request in #wspr-project and AI resources can generate a targeted report.
Q: How many members need to participate for this to be useful?
Even a single beacon is immediately useful to you personally — you will start seeing your propagation data right away. The project becomes genuinely interesting for the club when we have three or more stations on the air simultaneously. At that point we can begin making direct comparisons between stations and building a picture of how local terrain and antenna differences affect propagation from different parts of Gloucester County.
With five or more active beacons — our initial target — the analysis becomes quite rich. We get geographic diversity, multiple antenna types to compare, and enough statistical depth to identify real propagation phenomena rather than noise. Five is the threshold where the project moves from interesting to genuinely valuable as a club research tool.
Q: What happens with the data — is it public or just for the club?
All spot data is fully public and always will be. When your beacon transmits and a receive station hears it, that spot is uploaded to wspr.live and wsprnet.org immediately — visible to every WSPR operator in the world. This is by design: the power of the WSPR network comes from global participation and open data.
The club-specific analysis — comparison reports, rankings, and AI-generated summaries — are club-internal products built from that public data. Think of it the same way as weather stations uploading to Weather Underground: your data is yours and it is also part of something much larger than any individual station.
Q: Will there be ongoing club meetings or presentations about this?
Yes — this is designed to be a living project, not a one-time build event. We plan to include a regular WSPR Network update at monthly meetings covering band conditions, notable propagation events, interesting spots, and member antenna comparisons. Over the summer we will run a series of Saturday sessions including antenna presentations and a hands-on antenna-building session.
There is also a dedicated Discord channel (#wspr-project) where members can share interesting spots, ask questions, and see automated reports as they are generated. The goal is to keep the project active and engaging for the long term — not just build the beacons and forget about them.
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ADDITIONAL RESOURCES
All of the following are available under Technical Resources on the Skunkworks website at skunkworks.w2mmd.org:
• Full project documentation and build guides
• wspr.rocks — real-time WSPR spot map and query interface
• wspr.live — full spot database, 4 billion+ records
• wsprnet.org — original WSPR spot database
• tapr.org/product/wspr — order the TAPR Universal WSPR HAT kit ($32)
• adafruit.com/product/6008 — Raspberry Pi Zero 2W with headers ($15)
• github.com/lbussy/WsprryPi — WsprryPi software (free, open source)
• raspberrypi.com/software — Raspberry Pi Imager (OS download)
W2MMD · Gloucester County Amateur Radio Club · w2mmd.org · Spring 2026