When the cell network disappears — in a forest, in the mountains, at a country house or during a mobile internet shutdown — what is left are means of communication that need no towers. Here are four common options for private users and how they differ.
Ordinary PMR and LPD walkie-talkies
PMR (446 MHz) and LPD (433 MHz) radios are sold in any outdoor shop and work right out of the box. Voice is real-time: press and talk. Range depends on terrain: usually hundreds of metres in a city, kilometres in open country. There is no relaying: if you cannot hear the other person directly, there is no link. Cheap models have no text, location or encryption, and anyone on the same channel hears the conversation.
Meshtastic
Meshtastic is open firmware for boards built around LoRa radio modules: Heltec, LilyGO, RAK and others. The boards form a network in which each one passes messages on, so text reaches beyond line of sight. It has encryption, positions on a map, a large community and thousands of nodes worldwide. There is no voice: the protocol is designed for short messages every few seconds.
MeshCore
MeshCore is another firmware for the same boards. Its network is built on dedicated repeaters, which saves airtime when there are many users. Like Meshtastic, MeshCore carries text. People in our group add voice in their own ways: Dmitry, for example, built a separate module that reads incoming messages aloud.
MeshTRX
MeshTRX is firmware for Heltec WiFi LoRa 32 boards plus a phone and desktop app that add voice. The phone compresses speech with the Codec2 codec to 3200 bit/s and sends it over the air through the board. Besides voice there is text up to 84 characters, photos up to 100 KB, positions on a map, calls to everyone or one person, a repeater and encryption. MeshTRX is an independent project and does not talk to Meshtastic or MeshCore networks: every participant needs a board running MeshTRX.
In field tests voice holds up to two kilometres in a city, text goes further. Distances grow with height: a station on high ground adds more than transmit power does. Details are in the article on range.
Comparison
| PMR/LPD radios | Meshtastic | MeshCore | MeshTRX | |
|---|---|---|---|---|
| Voice | yes, instant | no | no | yes, up to 10 s per transmission |
| Text | no | yes | yes | yes |
| Relaying | no | every node | repeaters | repeater |
| Encryption | usually no | yes | yes | yes |
| Needs a phone | no | yes, for text | yes, for text | yes, or a computer |
| What to buy | two radios | two boards | two boards | two boards |
Which to choose
If you only need voice and do not want to deal with firmware, ordinary radios will do. If a large network and messages far beyond line of sight matter most, use Meshtastic or MeshCore. If you already have a Meshtastic board and want phone voice, text and a map in one app, MeshTRX turns the same board into a radio after flashing it from the browser.