Small, cheap radios that send text messages and positions from one to another with no phone service, no internet and no license. Every radio in range passes messages along, so a few of them spread out over a neighborhood or a valley reach further than any one could. The free software they run is called Meshtastic. Each radio talks to a phone by Bluetooth: you type and read on the phone, the radio does the sending.
This guide covers what to buy, what to do now, while there is internet, setting a radio up, keeping messages private, getting range, linking up with neighbors, power, and fixing problems. The project's own manual is on the drive too: the Meshtastic documentation, offline copy (325 pages, in Comms-Signals\Mesh-Radio), with the phone app beside it. The ARK Vault has two of these radios: see The ARK Vault's mesh radios.
⚠️ Rules that prevent the worst outcomes
Antenna on before power, every time. A radio that sends with no antenna can burn out its radio chip (docs, p. 64; p. 264).
Set the region to US before anything else. With no region set, the radio does not send at all (docs, p. 74).
The ready-made channel is public. Its key is printed in the software, so anyone with a Meshtastic radio in range can read it. Use a private channel for anything private (docs, p. 160).
It is text, not voice, and not a way to reach 911. In an emergency, also use the Radio guide and the Signals guide.
Put the app and the radio's software on now. Both are downloaded from the internet.
1. What it is, and what it is not
It does
It doesn't
Short text messages, up to about 200 letters each (docs, p. 108)
Voice, pictures or files
Messages to a whole group (a channel) or to one person
Reach the phone network or 911
Share where each radio is, on a map in the app
Work without a phone, mostly (the radio has no keyboard)
Pass messages along: up to 3 radios in a row by default, 7 at most (docs, p. 133)
Get through a big ridge on its own
Run for days on a small battery
Need a license, a tower or a monthly bill
How far(rule of thumb): through thick forest or over hills, ¼ to 1 mile; around town, 1 to 3 miles; with a clear view across a valley or from a hilltop, 5 to 20 miles or more. People have reached over 200 miles from mountain to mountain (docs, p. 30). What matters most is height and a clear line between the radios, not power.
Why it works when phones don't: the radios use a free band (902 to 928 MHz in the US) that anyone may use at low power, and each one repeats what it hears. There is nothing in between to fail but the radios themselves.
2. What to buy
Get radios made for the 915 MHz band (sold as "US 915" or "902-928 MHz"). The ones sold for Europe (868) or Asia (433) will not talk to American radios.
Kind
Example
Good for
Pocket radio with its own battery and GPS, nothing to set up
SenseCAP T1000-E (card size, rain-proof, about $40)
Carrying, one per person; the ARK Vault's pocket radio
Board with a screen
Heltec WiFi LoRa 32 V4 (about $25, plus a battery and a case)
A radio at home or in a car; the ARK Vault's own radio
Low-power board for a solar relay
RAK WisBlock (nRF52 kind)
A relay on high ground that runs on a small panel
Ready-made relay in a weather-proof box with a solar panel
sold by several makers
A neighborhood relay with no building
Also: a USB-C cable that carries data (not a charge-only one: test it by copying a file), a 915 MHz antenna for boards that don't have one built in, and a power bank for each radio.
Tip: buy the same kind for everyone in the household: one way of charging, one set of buttons to learn.
3. Do these now, while there is internet
Put the app on every phone. Android: Meshtastic from Google Play, or the copy on this drive, Meshtastic app for Android (copy it to the phone, tap it, and allow installing from that source when the phone asks). iPhone and iPad: Meshtastic from the App Store. An iPhone cannot install it later from a file.
Put Meshtastic on each radio if it didn't come with it, and bring it up to date. On a computer with Chrome or Edge, plug the radio in with a data cable and open flasher.meshtastic.org (docs, p. 67). Pocket radios like the T1000-E come with it.
Set each radio up (next section): region US, a name, and the household's private channel.
Print the channel's QR code and the card in section 13, and keep them with the radios.
Test: send a message each way, then walk until it stops arriving, so you know your range.
Find your local mesh: neighbors may already run one. Ask what channel and preset they use (docs, p. 79).
4. Setting up a radio, step by step
Antenna on, then switch on (the T1000-E: hold its button until it beeps).
Connect the phone: in the app, open Connect, tap Scan for Bluetooth devices and pick the radio. Type the 6-number PIN the radio shows on its screen; a radio with no screen uses 123456 (docs, p. 93).
Set the region: tap SET YOUR REGION (or Settings → LoRa), choose US, tap Send (docs, p. 74). The radio restarts.
Check the preset is Long Fast (Settings → LoRa). Every radio that should talk to yours must use the same one. A radio whose region was first set on its own screen starts on Long Turbo, which cannot hear Long Fast: change it (docs, p. 131).
Give it a name: Settings → User: a long name (Dad's radio) and a 4-letter short name (DAD). That is what others see.
Add the household channel (next section) and send a test message.
The Vault's Heltec board: in the web flasher choose Heltec LoRa32 V4. If the big chip on the board reads ESP32-S3R8, choose V4-R8 instead: the two take different software (docs, p. 268).
5. Channels: who can read what
The primary channel comes ready-made, named LongFast, with a key everyone has. It is how strangers' radios find each other and pass messages along. Treat it like shouting in the street.
A private channel has a random key that only the radios you give it to have. Make one for the household: Settings → Channels → add a channel and give it a name (the app makes a new random key for it), tap Save, then Send to put it on the radio (docs, p. 100). A radio holds up to 8 channels.
Sharing it: the app shows the channel as a QR code. On each other phone, scan it with the app. Typing the same name by hand does not work: the random key is in the code, and the code carries the radio settings too (docs, p. 29). Only scan codes from people you trust, for the same reason.
Direct messages (to one radio, from the Nodes list) are locked to that person, so other people on the same channel can't read them either. Your radio must have heard the other radio first (docs, p. 101).
Your position: on the public channel it is only shared roughly (about half a mile). On a private channel you choose how exact (docs, p. 154).
The lock in the app tells you: green, private; yellow, readable by anyone; red, readable by anyone and sharing exact positions (docs, p. 100).
6. Sending messages and positions
To the group: open the channel in Messages and type. A message to a channel only shows that it went out; no one confirms reading it.
To one person: tap them in Nodes, then message. You see Delivered when their radio has it (docs, p. 102).
Keep it short: who, where, what, what you need. "DAD at barn. All OK. Back 5pm."
Positions: the map in the app shows every radio that shares where it is. The T1000-E sends its position when you press its button twice; three presses turn its GPS off or on to save the battery (docs, p. 302).
Waypoints: drop a marked point on the app's map (a meeting place, a water source) and it appears on everyone's map on that channel (docs, p. 119).
Did it get through, and which way? In Nodes, Traceroute shows which radios a message passed through (docs, p. 257).
7. Range: getting a message across
Get it high. A radio on a roof, in a tree or on a ridge reaches many times further than one in a pocket. Five feet up a fence post beats being on the ground.
Antenna straight up, and clear of metal and of your body. Indoors, by a window that faces the other radio.
Check the line between two places before carrying a radio there: on the library's map, Measure two points, and it says whether one can see the other, which is what a radio link needs (Maps guide).
Relay over a ridge: a radio on the ridge top between two valleys passes messages both ways. It should stay switched on, on a solar panel (section 10).
A better antenna helps more than more power: a longer, upright 915 MHz antenna on the house's highest point, with short, good cable (docs, p. 261).
Wet trees and leaves soak up the signal. Range in a wet forest in winter can be half of what it is in a dry summer (rule of thumb).
8. Roles: which job each radio does
Settings → Device → Role. Leave almost every radio on Client: it already passes messages along. The others are for special places (docs, p. 166; choosing a role, p. 179).
Role
Use it for
Client
Every radio people carry or keep at home. The right choice nearly always
Client Mute
Several radios in one house: one passes messages along, the others only listen and send
Client Base
Your own radio on the roof: it always passes on messages to and from the radios you mark as favorites (your family's)
Router
Only a radio in a high, open place everyone agreed on (a ridge-top relay). Routers always repeat, so one in a low or crowded place clogs the mesh for everyone
Tracker
A radio that only reports where it is (on a pack animal, a vehicle)
9. A neighborhood mesh
A mesh is only as good as the radios in it. A street where several houses keep one radio on all the time, with one relay up high, can reach across a whole valley.
Agree one private channel for the neighborhood (separate from each household's) and share its QR code in person, on paper.
One or two relays on high ground, set to Router, on solar power, with the owner's permission (section 10).
A check-in time: every evening at 7, each house sends "OK" or "HELP" and what it needs, the radio side of the neighborhood OK/HELP plan.
Short names that say who: OAKS for the Oaks place, not a gadget's number.
Pocket radio (T1000-E): about a week on a charge if its GPS is off or reports rarely, a few days if it reports often (rule of thumb). It charges from a magnetic USB cable: keep that cable with it, nothing else fits (docs, p. 302).
Boards with screens use more: run them from a power bank, and switch the screen to turn off after a while.
A solar relay: a small panel (5 to 10 watts), a battery pack that charges and powers at the same time, and a weather-proof box, with the antenna on top. The low-power (nRF52) boards run a long time on very little. Power planning: the Off-grid power guide.
Stored for an emergency: charged every few months, in a sealed metal box with the phone (see the EMP guide).
11. The ARK Vault's mesh radios
The Vault can hold two radios: a Heltec board under the lid, powered whenever the Vault is on, and a T1000-E pocket radio taped to a second phone, for whoever goes out. Each talks to its own phone through the Meshtastic app. Fitting them, and the steps to do before the can is sealed, are in the Vault guide. Screw the antenna on before flipping the Vault's switch.
The Vault's own mesh pages
Messages and a People layer on the map, for any phone on the Vault's Wi-Fi
The Heltec board under the lid is plugged into the Pi by its USB cable, and the Vault reads it. So any phone on the Vault's Wi-Fi gets the mesh with no Meshtastic app and no Bluetooth pairing:
More → Mesh messages: read what the mesh has said and send a message back. The row only appears when a radio is actually plugged in.
The map's People layer: a dot for each radio that knows where it is, its name, and a dashed trail of where it has been. Tap one for when it was last heard. A dot nobody has heard from for an hour fades, so an old position never looks like a live one.
This is useful for a phone with no app, for a visitor, and for anyone who would rather read a big screen. It does not replace the app on your own phone: the app still does direct messages and works away from the Vault.
⚠️ Three settings decide whether this is any use
Anyone who should appear on the map needs a radio that knows where it is. Position comes "from either the radio or your paired phone" (docs, p. 183). The T1000-E pocket radio has its own GPS. A plain Heltec board has none, so it shows on the map only if a phone is paired to it and sharing, or you set its position by hand.
Use a private channel, with full precision. On a channel with no key, the ready-made key or a one-byte key, "the firmware limits precision to 15 bits" (docs, p. 154) — about 790 yards, so the map draws a circle that size instead of a dot. On your own channel set Position precision to 32 for the exact spot. Section 5 makes the channel.
A dot moves every 15 minutes by default (Broadcast Interval, "Default of 0 is 15 minutes", docs, p. 184). Smart Broadcast sends sooner while someone is moving and less when they stop, and the docs say to leave the interval alone if you use it (p. 184). A shorter interval costs battery and airtime.
Sending a spot to everyone: waypoints
A waypoint is a named spot that shows on the map in everyone's Meshtastic app: "water here", "meet at this bend", "road blocked". On the Vault's map, tap the place, then Send to the mesh, give it a name, pick a mark and send. Anything the mesh sends back the same way shows on the Vault's map too. It is the only way to put something on a walker's map from home.
⚠️ A waypoint cannot be kept private, unless your main channel is private
The radio sends waypoints "to the whole mesh on the primary channel", and one "cannot be addressed to one channel or sent as a direct message" (docs, p. 120). So if your first channel is the ready-made public one, every waypoint you send is public — the spot, its name and your note.
The fix is in how you set the radios up, not something to change later: make your household's private channel the first channel (channel 0), not a second one alongside the public one. Changing it afterwards means redoing every radio, so decide at the start.
A whole route cannot be sent over the radio. A mesh packet holds a couple of hundred letters, and a route is hundreds of points: it would fill the air and still not arrive. Send a few waypoints for the turns that matter. For the whole thing, download the route's GPS track from the Vault before anyone leaves (walking routes) — it goes into any phone map app, and needs no radio at all.
Everyone on the Vault's Wi-Fi can read every message and see every position. That was a deliberate choice: in an emergency the people round the Vault are the people who need to know. If that is wrong for you, do not put the radio's private channel on the Vault's own radio.
Proving the cable before you trust it
One setting and one command, to check the Pi can really hear the radio
Worth doing once, before you rely on any of it. It needs no programming and proves the cable, the port and the permissions in about five minutes:
In the Meshtastic app, on the Vault's Heltec board: Settings → Serial, turn the module on, set the mode to CalTopo, and turn on Override console serial port. Save.
On the Pi, in a terminal: cat /dev/ttyACM0 (if nothing comes, try /dev/ttyACM1 or /dev/ttyUSB0).
Lines of text should appear every ten seconds, one per radio that knows where it is. If they do, the Pi can hear the radio and everything else is just software.
Put the Serial mode back to the default and turn the override off. While it is on, the Vault's own pages cannot use the radio: only one thing can have that cable at a time.
If nothing appears: check the USB cable is a data cable, not charge-only; check the radio's screen is lit (it only has power when the Vault's switch is on); and if the terminal says "permission denied", the Vault's library program needs to be in the dialout group.
12. The law, privacy and safety
No license needed in the US on the 915 MHz band at Meshtastic's normal settings (docs, p. 14).
Ham radio settings (the "licensed" mode, and the ham-band regions) are only for licensed amateurs. In that mode messages may not be locked (encrypted), and your call sign is the radio's name. Licensed and unlicensed radios don't talk to each other (docs, p. 77; p. 307).
Anyone can listen to the public channel, and see positions shared on it. Some radios also pass the public channel to the internet when they have it. Keep names, addresses and plans to private channels.
Change the Bluetooth PIN from 123456 on a radio with no screen, so a stranger nearby can't connect to it (docs, p. 216).
A lost radio: it holds your private channel's key. Make a new channel and share the new code with everyone else.
13. Print-and-keep mesh card
Household
Neighborhood
Channel name
QR code
(stick a printout here)
(stick a printout here)
Region / preset
US / Long Fast
US / Long Fast
Check-in time
Meeting place if messages stop
Short name
Who
Where it usually is
Message form: WHO · WHERE · OK or HELP · WHAT YOU NEED · WHEN YOU'LL CHECK IN AGAIN.
14. If this goes wrong
Problem
Try
Two radios don't see each other
Same region (US), same preset (Long Fast), same channel and key? Scan the QR code again rather than typing
A radio set up from its own screen hears nothing
It started on Long Turbo: set Long Fast (docs, p. 131)
The app can't find the radio
Bluetooth on, the app allowed to find nearby devices, the radio near the phone. Still no: forget the radio in the phone's Bluetooth settings and pair again (docs, p. 93)
Asked for a PIN you don't know
It is on the radio's screen; no screen, 123456
Messages to a channel never seem to arrive
Out of range: get higher, add a relay, or send a direct message to see Delivered
A direct message won't send
Your radio hasn't heard theirs yet. Wait until they show in Nodes
The T1000-E can't hear an old radio
Some older radios (SX127x chip) can't be heard by it directly; it works through a third radio (docs, p. 301)
The battery dies fast
GPS on and reporting often: report less, or turn GPS off (T1000-E: press 3 times)
A radio needs new software and there's no internet
It can't be done offline from this library: carry on with what it has. All radios on 2.x software still talk to each other