One receiver in a good spot — a windowsill, a clubhouse roof — hears every transmitting boat within ~40 nm, 24/7, for a few dollars of power a year. It quietly records them all, so those races are caught and ready to replay — nobody has to switch anything on. (Boats not on AIS still join with a phone or a GPX file, which also fills any gaps.) It's the single biggest set-and-forget thing you can do to see more of your racing, and you can start today with a PC you already own.
Three steps: 1. get an RTL-SDR dongle and an antenna (google 'RTL-SDR dongle') — what to buy · 2. sign in and download your ready-to-go receiver below · 3. plug it in and run it. Your fleet's on the map.
Set up one shore station at the club once, and it records 24/7 on its own. No app to launch, no tracker to hand out, nothing for the race committee to switch on. After racing you just go back to the date and time — the whole fleet is already AIS-tracked, ready to open as a replay in a few clicks. Miss the start? It's recorded. Protest? It's on the timeline.
One box on the clubhouse roof, and every race is captured — ready to publish as a replay whenever you like.
Racing yachts broadcast on low-power Class B AIS that only carries a few miles. The global networks pick up the big ships from far off — but the little boats stay under their horizon. Only a receiver near the water catches them.
One recent Wellington race afternoon, of the boats transmitting AIS:
| 🏁 Race boats caught by a local receiver a boat on the water + a clubhouse dongle | 5 of 5 |
| …and how many the global network heard | 1 of 5 |
The wide networks are a great free bonus — that day they added hundreds of ships, ferries and distant vessels of context. But the racing that matters to your club is only ever captured locally. That’s why every receiver counts: one on your windowsill sees races nobody else can.
If you already feed AISHub, MarineTraffic or VesselFinder, you can feed Telltale too — receivers happily output to several networks at once. Point one more output at us:
AIS-catcher ...your existing options... -H https://telltaleracing.com/api/ais-ingest?key=YOUR_KEY INTERVAL 10(or POST the same AIS-catcher JSON to that URL from whatever you run).
Your feed stays yours. Because it comes straight from your receiver, it's clean, publishable data — not subject to another network's redistribution rules.
So your feed comes back by itself after a power cut or reboot, run AIS-catcher as a systemd service. On a Pi/Linux box (fill in YOUR_KEY):
sudo tee /etc/systemd/system/ais-telltale.service >/dev/null <<'EOF' [Unit] Description=AIS-catcher feeding Telltale After=network-online.target Wants=network-online.target [Service] ExecStart=/usr/local/bin/AIS-catcher -d:0 -H "https://telltaleracing.com/api/ais-ingest?key=YOUR_KEY" INTERVAL 10 Restart=always RestartSec=10 [Install] WantedBy=multi-user.target EOF sudo systemctl daemon-reload sudo systemctl enable --now ais-telltale
Check it with systemctl status ais-telltale. Already run AIS-catcher for another network?
Don't start a second one competing for the same dongle — just add the -H … output to your existing
service and restart it. Setting up a fresh Pi? Our one-line Pi installer (provision.sh) sets up the service for you — the ready-to-paste command is in your key box above.
📶 On a boat with a backup connection? Give the Pi both WiFi networks (yours primary, a marina/phone hotspot as failover) so the feed keeps flowing if one drops — it only pushes out, so it works fine over any connection.
You almost certainly don’t need this — the download in your key box above already bundles everything
(the tool, the driver installer, your key) into one START HERE.bat, and it works even if antivirus blocks web installers.
This is only the raw ingredients if you’d rather wire it up yourself.
Turn a cheap ESP32 into a plug-and-play gateway that re-serves your boat's instruments over WiFi. Flash one of these and follow the guide:
Or a full shore station (Pi + RTL-SDR): our one-line Pi installer (provision.sh) does everything — the command's in your key box above.
If your boat already outputs NMEA 0183, you don't need to build anything. A cheap serial-to-WiFi server (an Elfin EW11 — google 'Elfin EW11' — 9–36 VDC, an industrial-IoT part, not marine kit) puts your instruments on WiFi. Then one small always-on device (a Pi, an old phone, the nav laptop) runs our bridge and feeds Telltale:
Two wires, one command — sends your own track (GPS + wind/speed/heading/depth/heel), logs every fix locally, and buffers at sea to upload ashore. No Signal K, no Starlink needed.
📡 Not sure which to buy? Compare all the options & costs →
Feeding from a boat is easy and it won't chew your satellite/cellular data unless you want it to. Two ways to keep it cheap:
--defer records everything to the SD card and sends nothing
while you're out; back on marina/club WiFi it flushes the whole trip in one go.--sip keeps the full signal set but uploads a light trickle every couple of minutes —
add --fleet to trickle just the race boats (10, not 300 harbour targets).--auto switches by which link is live: cheap cellular up → full, Starlink-only → sip or defer.Either way, your data stays yours — it's always logged locally and exportable. Live streaming is opt-in, not required.
See who's feeding and the coverage they light up on the 📡 feeder coverage board →
Fill this in and copy the result into ~/telltale-device.conf on your device — the connector reads it
automatically, so you never have to remember a flag.
Then on the device:
A receiver hears every AIS-equipped boat in view, 24/7, for a few dollars of power a year — and one well-placed box can cover a club’s whole harbour. The software is all free (AIS-catcher / Signal K + our connector). There are two easy ways in:
Any always-on computer with a glimpse of the water and a small AIS aerial in a USB port works surprisingly well — we’ve run one on nothing more than a stubby 15 cm aerial and it happily heard the harbour. It won’t match a masthead antenna, but it’ll get you contributing today, and you can always upgrade later.
For a set-and-forget club station: a small single-board computer (a Raspberry Pi is ideal — silent, low-power, runs unattended for months) plus an AIS receiver and a marine VHF antenna. Two receiver options:
What actually decides range: height and a clear view of the water. A longer, higher antenna hears far more than a bigger computer ever will — a marine VHF whip up where it can see the harbour is the single best upgrade. Get the aerial right and even modest kit reaches well.
Ready? Ask the admin for the one-line installer and a station key and you’re on the map.
Your station credited on the map, the satisfaction of building a free, open, NZ-built marine commons — and every race in your area captured in the background, ready to open as a replay. Thank you. 🙏