Build a LoRa APRS tracker or iGate

A board for a few tens of euros, the CA2RXU firmware and an hour: a tracker or an iGate, no soldering, flashed from the browser. You’ll see it on the LoRa APRS map.

What you need

  • An amateur licence and callsign. LoRa APRS transmits in the 70 cm band, so check that your licence covers 70 cm.
  • An ESP32 board with LoRa on 433 MHz (not 868 or 915: that’s different hardware and no setting will change it).
  • An antenna for 433 MHz. The stubby one in the box works; a good 70 cm antenna up high gives many times the range.
  • A USB cable that carries data (not charge-only) and Chrome or Edge on your computer.
  • For an iGate: WiFi where it will sit.

Never power the board without an antenna. The first transmission can burn out the LoRa chip.

Which board

all supported by CA2RXU
BoardForNote
LilyGO T-Beam (V1.1, V1.2, Supreme)TrackerGPS and an 18650 battery holder on board. The easiest way into trackers.
LilyGO LoRa32 V2.1 / T3S3iGate or digiCheap, with a display. No GPS: you enter the position by hand.
Heltec WiFi LoRa 32 V3 / V4iGate or digiWhat SV2RIM-10 runs on. Small, with a display, USB-C.
Heltec Wireless TrackerTrackerGPS and a colour display.
Full list: iGate and tracker.

Settings for Greece

the same for everyone
SettingValueWhy
Frequency433.775 MHzSame for RX and TX. All of Europe, Greece included.
Spreading factorSF12Slow but long range. On any other SF nobody will hear you.
Bandwidth125 kHz
Coding rate4/5
Power20 dBm (100 mW)The default. Enough for tens of km from a high site.
PathWIDE1-1One hop. Don’t use WIDE2-2 on LoRa: it floods the channel.
In Greece: 433.775 MHz, not the presets for Poland or the UK.

A. Tracker, step by step

  1. Screw on the LoRa antenna (and the GPS antenna, if it’s separate).
  2. Plug the board in over USB and open the tracker web flasher in Chrome. Pick your exact board (e.g. T-Beam V1.2, 433 MHz) and click Install. If no port shows up, you need the CP210x or CH9102 driver.
  3. After the reboot, open the setup page over the board’s own WiFi, as the tracker configuration guide describes. The setup WiFi turns itself off if you don’t connect within a minute.
  4. Enter your callsign with an SSID, e.g. SV2XXX-7 for a handheld or -9 for a car. Leave SmartBeaconing on: it beacons often while you move and rarely when you stop.
  5. Check that the LoRa profile is 433.775 MHz · SF12 · CR 4/5 and the path is WIDE1-1.
  6. Go outside for a GPS fix (a few minutes the first time). As soon as an iGate hears you, you appear on the LoRa APRS map.

Over Bluetooth the tracker also works as a TNC for APRSdroid (Android) or the aprs.fi app (iPhone), for messaging.

B. iGate or digipeater, step by step

  1. Screw on the antenna. Plug in over USB and open the iGate web flasher. Pick your board and click Install.
  2. On first boot, with no WiFi configured, the board opens its own access point called NOCALL-10-AP with password 1234567890. Connect from your phone and open the setup page (usually 192.168.4.1).
  3. Fill in:
    • Callsign: SV2XXX-10.
    • WiFi: your home network.
    • Beacon: latitude and longitude in decimal degrees (e.g. 40.80, 22.05), a comment such as “LoRa APRS iGate Edessa”, symbol L& for an iGate or L# for a digipeater.
    • APRS-IS: enabled, server aprs.sv2r.im (SV2RIM’s Greek server) or rotate.aprs2.net, port 14580, passcode from the calculator below, filter m/10.
    • LoRa: RX and TX on 433775000 Hz, SF12, CR 5, BW 125000.
    • Web password: set your own admin password, or the setup page stays open to your whole local network.
  4. Pick a role:
    • RX-only iGate: TX off, digipeater off. Gates everything it hears. The simplest setup.
    • iGate with TX: TX on, so messages from the internet reach trackers.
    • Digipeater: only on a high site that covers an area with no other digi. Mode WIDE1-1. Two digis that hear each other double the traffic.
  5. Save. The board restarts, joins your WiFi and sends a beacon. Within minutes you appear in the iGate list on the LoRa APRS page.

APRS-IS passcode

worked out in your browser

An iGate needs a passcode to write to APRS-IS. It comes from your callsign without the SSID. Nothing is sent anywhere.

–

Which SSID

convention, not a rule
SSIDFor
-10iGate
-1, -2, -3Digipeater (or -10 if it’s also an iGate)
-7Handheld tracker
-9Vehicle tracker
-13Weather station

Not showing up on the map?

  • Tracker: does it have a GPS fix? Is there an iGate within range that can hear you? Check the map for nearby iGates.
  • Wrong frequency or SF: everyone must be on 433.775 MHz, SF12, CR 4/5.
  • iGate: is the passcode right? Is APRS-IS enabled? Does the display show it connected to WiFi and to the server?
  • 868 MHz board: it can’t be turned into 433. You need another board.

Sources