When it isn't working.
Almost every problem on the mesh is one of five things. Take them in the order below, because until an earlier one is right you cannot trust what the next one is telling you. Deal with the first failure you find and try again before reading further.
The order to check in
Do your radio settings match everyone else's?
This is the most common cause by a distance. Get the frequency, bandwidth, spreading factor or coding rate wrong and your radio still transmits perfectly, into a room where every other set of ears is tuned somewhere else. Compare yours against the settings every radio here runs. If you set the radio up with flasher.lhtx.org, these are already right and you can move on.
Have you actually announced yourself?
Two radios cannot talk until each has heard the other's advert, because that is when they exchange keys. A new radio with an empty contact list is behaving correctly. Nothing on this network introduces you except you, so send a flood advert from the app and then be patient: names arrive over the following day or two as those adverts work their way outward.
Is anything actually in range?
Find out what you can hear before deciding nobody can hear you. Elevation does more than wattage ever will, and lifting an antenna a few feet will beat any number you could type. Indoors, under a metal roof, or down in the river bottom, walk outside and up before changing anything else.
Has the radio gone deaf?
A receiver that worked this morning and hears nothing this afternoon has usually been swamped by a burst of nearby interference and never recovered its sensitivity. Restarting it clears that. If it returns, something close by is transmitting in the same band.
Is the link one-way?
When neighbors report hearing you and nothing comes back the other way, the fault is in what your radio receives rather than what it sends. Look at the antenna seating first, then any cable between it and the board, then whatever else is switched on around it.
Straight to the symptom
| What you see | First thing to try |
|---|---|
| Nobody hears me | Check your radio settings match, character for character. Then send an advert. |
| My contact list is empty | Expected on a new radio. Send a flood advert, then give it a day or two to populate. |
| I get through, but only just | Get the antenna higher. Try that before touching any number. |
| It worked earlier, now nothing | Restart it. Lost sensitivity after interference is the usual reason. |
| They hear me, I hear nothing | Look at what you receive with: antenna seating, cable, nearby transmitters. |
| Messages leave but never land | Your neighbors are holding an out-of-date path. Advert again so they refresh it. |
Advert again after you change anything. Move the node, swap the antenna, or alter a setting, and every neighbor is still holding the path that worked before. They will keep routing to a version of you that no longer exists. It is a quietly common failure, because the radio looks perfectly healthy while the mail goes nowhere, and a single advert clears it.
Reading the numbers
A repeater will tell you what it is hearing if you ask it over the serial console. Two commands do most of the work.
stats-radio noise floor, last signal and quality
neighbors who this node hears, and how wellThree numbers come back. Signal strength, in dBm, measures how loud an arriving transmission is. The noise floor measures the general hiss the receiver has to listen through. Signal-to-noise, in dB, is the gap between those two, and it is the one worth judging a link on.
| Number | Healthy | Marginal | Trouble |
|---|---|---|---|
| Signal strength | above −100 dBm | −100 to −118 | below −120 |
| Signal-to-noise | 0 dB or better | 0 down to −7 | below −7.5 |
| Noise floor | −120 dBm or quieter | −120 to −110 | above −105 |
Judge a link on signal-to-noise, not loudness. Plenty of signal arriving into a hissy location will still fail to decode, so strength read on its own will flatter a link that does not work. A negative figure is not automatically a fault either: these radios are designed to recover a transmission buried beneath the surrounding noise, which is much of why they carry as far as they do. At the spreading factor we run, decoding gives out somewhere around −7.5 dB.
Two ways to kill a radio
- Never transmit without an antenna attached. With nothing to radiate into, the power comes back into the output stage and can destroy it. Screw the antenna on before you power the radio up, every time, and never send a test message on a bare board.
- Do not exceed your board's transmit power. We run 22 dBm or the board's maximum, whichever is lower. Setting a number the hardware cannot deliver does not get you more range; it gets you a hot amplifier and a distorted signal.
Still stuck
Ask in the Facebook group or email hello@lhtx.org. Somebody has almost certainly hit the same thing.
You will get a useful answer much faster if you say up front:
- Which board it is, and whether it is a companion or a repeater.
- Which firmware version, and how you flashed it.
- What you expected to happen and what happened instead.
- Anything
stats-radioorneighborsreported, if it is a repeater. - Roughly where the radio is, and how high.
The order of checks on this page owes something to the troubleshooting guide published by NashMesh, a mesh community in Nashville. They are an independent group on the same open MeshCore network. The wording here is our own, and so are the mistakes.