MeshTRX
Off-grid voice communication via LoRa mesh network
Voice, messages and files with no internet and no cellular. Heltec V3 or V4, an Android phone, and conversations closed by a group key.
How it works
Flash Heltec V3 or V4
V3 flashes over USB right in the browser. For V4, download the file for your revision from the download page.
Install APK
Download MeshTRX app on Android and connect to the module via BLE.
Communicate
Voice, messages and files — everything works without internet via LoRa mesh.
Features
Voice communication
PTT voice over LoRa with the Codec2 vocoder at 3200 bps. Intelligible, with no internet.
Messages
Text messages with guaranteed delivery and confirmation.
File transfer
Send files over mesh network with fragmentation.
Map & Radar
GPS positions of all participants on map. Nearby nodes radar.
Group calls
Voice calls to entire channel or direct call to specific node.
Repeater
Any node can work as a repeater, extending network coverage.
Encrypted traffic
A group passphrase closes voice and text. The radio derives the key itself, and a four-character fingerprint is checked out loud. The repeater needs no key: it forwards the conversation without hearing it.
Channel handling
The radio walks all 23 channels and shows where it is quietest. One command moves the whole group to the chosen channel, repeater included — no need to walk up to each device.
Hardware
Heltec WiFi LoRa 32 V3 / V4
Both boards are supported
Which firmware for which board
| Board | What is inside | Firmware file |
|---|---|---|
| V3 | SX1262 with no external amplifier | firmware-v3.bin |
| V4 rev 4.2 | GC1109 front-end | firmware-v4.bin |
| V4 rev 4.3 | KCT8103L front-end | firmware-v4.3.bin |
The revision is printed in small type on the board next to the antenna connector. Firmware for the wrong revision will boot, but it drives the amplifier from the wrong pin: the device hears worse, or does not transmit at all. Download
Roadmap
The project is actively evolving. Here's what will be added in upcoming versions.
Encrypting files and beacons
Voice and text are already closed by a group passphrase. Files and beacons still travel in the clear, so call signs and coordinates are visible: a file-chunk packet carries no sender address, which means changing the format rather than wrapping the existing one.
Desktop client builds
The client already works and connects to the device over Bluetooth, just like the phone does. What is left is packaged builds for Windows and macOS: today it is installed from source, which shuts out almost everyone who needs it.
Zones and a trunk link
Three repeaters that hear each other cannot carry voice in one channel: a single talking station takes two thirds of the air. That needs zones, where a repeater only repeats its own stations, and a separate link between repeaters.
Long-range mode for text
Voice needs speed, and speed costs range. A separate slow mode for text will reach where voice no longer lives — field measurements showed the gap between them is wide.
Mesh routing
Improved routing algorithms for multi-hop networks with automatic optimal path selection.
More devices
Support for other LoRa boards: LilyGo T-Beam, RAK WisBlock, and other ESP32 + SX1262 modules.
Ready to try?
Download the app, flash the module and start communicating without internet.