🚲📡🗺️
Mesh Buddy: build your own GPS tracker
Shop it, build it, flash it, and watch yourself on aprs.fi!
G'day!
Mesh Buddy is a little GPS tracker you build yourself. It sends your position over the SEQ
MeshCore LoRa mesh, and a Kelly Page iGate passes it on to aprs.fi under your callsign.
No SIM card, no phone and no internet on the tracker. 🎉
This guide takes you from the shopping cart to your first ride on the map. Each step is short. If anything looks
different from what's written here, stop and give me a call. No harm done.
Cheers,
Alec VK4AZ
📜 Licensed hams only. Mesh Buddy sends your callsign, and aprs.fi is an amateur network. The LoRa
side runs on 915-928 MHz under the LIPD class licence (not on the ham bands), at about a quarter of a watt.
🛒 1️⃣ Go shopping at Core Electronics
Everything comes in one order from core-electronics.com.au.
Search for the SKU, or click the names:
Prices checked 31 October 2026. They change, so check before you order.
Also grab:
✅ A
3.7 V single-cell LiPo battery with a
JST PH 2.0 mm plug. 1000-2000 mAh is a good start.
✅ A
weatherproof case the GPS can see the sky through
✅ A PC with
Chrome or
Edge, and
Kelly Page
💡 Want an on/off switch? This board has none: you unplug the battery to turn it
off. For a switch, add a RAK19001 Dual IO Base Board (RW-110081, $21.80) and use it instead of the kit's
board. The GPS then goes in slot A instead of slot C.
🔧 2️⃣ Put it together
No soldering. Just a tiny screwdriver and a steady hand. 🪛
- The RAK4631 (the brains) clicks onto the base board's big core slot, if it isn't on already. Line up the
connector, press down evenly until it clicks, then fit its little screws.
- The RAK12500 GPS goes in slot C. The slots are labelled on the board. Press it on and fit its one screw.
In the wrong slot the GPS may show up but never get a fix.
- The GPS antenna clicks straight down onto the RAK12500's tiny socket. Its flat ceramic face goes
up, towards the sky. ☀️
- The LoRa antenna: click the U.FL end of the new cable onto the RAK4631's socket marked LoRa (not
the one marked BLE), then screw the antenna onto the cable's SMA end.
- The battery goes in last, after the check below.
⚠️ Antenna first, always. Never power the tracker without the LoRa antenna on.
Transmitting into nothing can damage the radio.
⚠️ Check the battery's wires before you plug it in. LiPo plugs are sold wired both ways round.
Compare the battery's red and black wires with the + and − marks beside the battery
socket. Backwards can destroy the board. If they don't match, don't plug it in: get a battery that matches.
📦 In the case: mount the LoRa antenna upright and as high as you can, away from your body. On the
first test ride, nearly every lost packet was lost on the bike's own first hop, so a good antenna spot is the
biggest improvement you can make.
⚡ 3️⃣ Flash it with Kelly Page
Kelly carries the Mesh Buddy software and puts it on the tracker over USB, straight from the browser. No
programming tools needed.
🔒 Kelly on a Raspberry Pi? Browsers only allow USB on a secure page,
and your Pi's http://kellypage.local:8025 address isn't one. So for flashing, use Kelly as a file on
your PC: unzip the Kelly Page zip into a folder, then open index.html from it in Chrome or Edge. That copy
is only for flashing. Your Pi keeps doing everything else.
Kelly on your PC with the bridge? Use your bridge's https:// address or
http://localhost:8025.
- In Kelly, open Admin › My station and type your callsign (for example VK4ABC).
Mesh Buddy uses this one. (Doing it from the file copy? Set the callsign there too, since each copy keeps its
own settings.)
- Open LoRa Mesh › 🚲 Mesh Buddy. Check the line "Goes on air as VK4ABC-12
named VK4ABC Buddy".
- Pick your bits: the SSID (-12 is the usual for a tracker, -9 for a car), the word after your
callsign (Bike, Ute, Walk…), the symbol 🚲🚗🚶, and an optional comment and status.
Leave the radio on SEQ / MBUG.
- Often riding at the edge of the mesh? Tick Patchy coverage. It beacons up to every 60 s
instead of 120 s.
- Plug the tracker into the PC by USB and click ⚡ Flash Mesh Buddy and set it up.
- Pick the tracker's port. It's usually the only new one.
- The tracker restarts as a new USB port. If Kelly asks, click
🔌 Choose the bootloader port and pick it.
- Flashing takes about 70 seconds. ☕ Don't unplug it!
- Kelly then sets your callsign, name, symbol and radio, and gives the tracker a new admin
password. ✍️ Write it down. Kelly also keeps it under My Mesh Buddies.
Changing something later? Plug it in and use ⚙️ Set up only. It doesn't flash again.
🗼 4️⃣ Set up your Kelly iGate
The iGate is the Kelly at home that hears your tracker on the mesh and passes it to aprs.fi. It needs a
MeshCore node at home plugged into your Kelly (on the Pi, a RAK, SenseCAP or XIAO node on USB is found by
itself). No home node? Skip to the tip at the end of this step.
Do this on your everyday Kelly (your Pi bookmark, or your PC with the bridge), not the flashing copy:
- Open LoRa Mesh and check your home node says it's connected.
- Open APRS iGate. It's right under Dashboard in the menu.
- Check the Callsign and pick the SSID. -10 is the usual one for an iGate, for example
VK4ABC-10. There's no passcode to enter: Kelly works it out for you.
- Turn on Gate the MeshCore nodes on my list to APRS-IS.
- In the 📡 MeshPRS frames card, turn on Gate MeshPRS frames. If it
says your node doesn't have the channel yet, press Add #meshprs to my node.
- Add your tracker: switch the tracker on near your home node (it says hello as it starts up). It
pops up in 🔎 Add my device, newest first. Press This is mine ➜,
then ✅ Add to my list. 🎯
- Leave Dry run on for now. Kelly shows exactly what it would send, without sending it.
💡 No home node? Ask a local Kelly iGate operator to add your tracker. Give
them its node name and the first 8 characters of its node key, both shown when Kelly finishes flashing.
🚀 5️⃣ First time out
- Take the tracker outside with a clear view of the sky. The first GPS fix takes a minute or two. Until
it has a fix, it sends nothing.
- On your home Kelly, open LoRa Mesh › 📍 MeshPRS. Your tracker appears on the map, and
the tracker test panel shows each beacon as it arrives, plus any it missed. 🗺️
- Happy with what you see? Flip the big switch from Dry run to 📡 LIVE. Kelly asks
once to make sure.
- Go for a spin! 🚲 Then look yourself up: aprs.fi/#!call=a/VK4ABC-12
(with your own callsign and SSID). There you are! 🥳
How often it beacons: when you've moved 100 m or turned a corner (more than 15°), but never sooner than
every 2 minutes (1 minute with Patchy coverage). Parked, it beacons every 30 minutes. Every MeshCore repeater that
hears it passes it on, so the first repeater can be several kilometres away.
Coverage depends on the repeaters along your route far more than on distance. Missed beacons come in runs
in the bad spots. That's normal.
📊 6️⃣ Telemetry: what your tracker reports
Mesh Buddy also sends a little health report every 10 minutes while moving and every 30 minutes
parked, and straight away if the battery gets low or the board gets hot. On aprs.fi, open your station and click
Telemetry to see the graphs. 📈
| Graph | What it tells you |
|---|
| 🔋 Battery | Battery voltage, 3.00-4.27 V. Full is about 4.2 V. |
| 📶 EchoSNR | How strongly you heard the nearest repeater pass your last packet on. Hearing it
repeated proves your packet made it through the first hop. |
| 🎯 Echo% | How many of your last 10 packets a repeater passed on: your first-hop coverage
score. |
| 🛰️ Sats | How many GPS satellites it's using. |
| 🌡️ Temp | The processor's temperature, a little warmer than the air in the case. |
Plus 8 on/off lights:
| ⚡ Charge on USB power | 🪫 LowBt battery under 3.5 V |
| 📍 Fix GPS has a fix | 🏃 Move on the move |
| 🔁 Echo heard a repeater pass it on | 🌊 Fld sent by flood (repeaters pass it on) |
| 🔄 Rbt just restarted | 🔥 Hot over 50 °C |
💡 Watch Echo% on a regular route. It shows you exactly where your
antenna or a new repeater would help most.
🎉🚲🎉
You're on the map with your own Mesh Buddy!
From now on, just switch it on (plug in the battery) and go.
🆘 If something goes wrong
Kelly says USB flashing needs a secure page: open Kelly as a file on your PC (see step 3), or through your
bridge's https address, in Chrome or Edge.
No port to choose: use the USB-C cable from the kit (some other cables only charge), and close anything else using the
tracker, like Kelly's own LoRa Mesh USB connection or the Meshtastic web page.
Kelly never finds the bootloader: click 🔌 Choose the bootloader port when it appears.
Still stuck? Quickly double-press the little reset button on the RAK4631, then try again.
Flashed, but not on aprs.fi: check in this order: a GPS fix (go outside), your callsign is the first or
second word of the tracker's name, the tracker is on an iGate's list, the iGate is LIVE, and a repeater is in
range.
Want Meshtastic back? Flash it again with the Meshtastic web flasher. Mesh Buddy doesn't stop that.
Anything else: give me a ring. 📞