MeshTRX runs on three revisions of the Heltec WiFi LoRa 32. All of them have an ESP32-S3 processor and a Semtech SX1262 radio, a 128×64 screen, Bluetooth and a battery connector. They differ in the amplifier, memory and USB, and each has its own firmware.
The revisions side by side
| V3 | V4 (rev 4.2) | V4.3 | |
|---|---|---|---|
| External amplifier | none | GC1109 | KCT8103L |
| Memory | 8 MB | 16 MB + PSRAM | 16 MB + PSRAM |
| USB | separate bridge chip | built into the processor | built into the processor |
| Firmware file | firmware-v3 | firmware-v4 | firmware-v4.3 |
The revision is printed on the back of the board near the GPS connector, something like "HTIT-WB32LAF V4.3". Firmware for another revision will start, but the amplifier will be switched by the wrong pin. We tried it: V3 firmware flashes onto a V4.3 without errors, and then the board stays silent.
What the amplifier gives
On a V3 the signal goes straight from the radio chip to the antenna. On a V4 there is an amplifier in between with a low-noise input: it raises transmit power and improves reception of weak signals. The cost is current draw: the amplifier takes a noticeable current while transmitting, and the battery needs thick wires.
Power is set in the app in dBm. For range tests start with the default 14 dBm: a member of our group got 2 km in a city on it, with one radio on high ground and stock antennas.
Which to pick
- V3 — if you already have one or want the cheapest pair. It is enough for a neighbourhood, a camp or a building site.
- V4.3 — if you are buying now. It is the current revision at sellers, and the amplifier gives range margin.
- V4 rev 4.2 is less common; it works like the V4.3 but with a different amplifier and its own firmware.
All revisions work together: a V3 and a V4.3 in one group hear each other.
868 or 433 MHz
Most boards are sold for 868 MHz, where MeshTRX has 23 channels. The V3 also comes in a 433 MHz version: 5 channels and at most 10 mW, support is still in beta. Radios on 433 and 868 MHz do not hear each other, so the whole group needs boards of one band, with antennas for that band.
Antennas and batteries
The short stock antenna is fine to start with. Height helps most: a radio on a top-floor balcony or a mast gives more than any antenna at ground level. People in our group use flexible 868 MHz whips, and for a fixed station collinear antennas about a metre long.
The battery plugs into the JST 1.25 mm connector; any 3.7 V Li-Po fits. Check the polarity: some sellers wire the plug the other way round. Meshtastic cases fit MeshTRX too; the H1 Case on Printables suits the V3, and Printables also has V4 models with room for GPS and a battery.
Picked a board? Next comes the flashing guide.