Diagnosing Meshtastic Network Problems

This guide covers systematic diagnosis of common Meshtastic network issues: nodes that can't hear each other, poor range, network congestion, and routing failures.

Diagnostic framework

Work from the bottom up: radio layer first, then routing, then application.

1. Radio layer: Can the nodes physically hear each other? Check RSSI/SNR.
2. Configuration: Are both nodes on the same preset and channel?
3. Routing: Is the path between nodes working? Use Trace Route.
4. Application: Is the app connected properly? Is the message actually sending?

Problem: Two nodes can't communicate

Check 1: Same preset?

Nodes on different presets cannot hear each other. Verify:

meshtastic --nodes  # Check modem_preset in the output

Both nodes must show the same preset (e.g., LONG_FAST or MEDIUM_SLOW). If different: change one to match the other.

Check 2: Same channel and PSK?

Nodes must be on the same channel with the same PSK. The default public channel (LongFast) has an empty PSK. If you've customized your channel, the other node needs the same configuration.

meshtastic --info  # Shows channel list with PSK hashes

PSK hash mismatch = nodes won't communicate even if physically in range.

Check 3: Physical range and line of sight

In the Meshtastic app, check if the node appears in the node list with any RSSI/SNR value. If it appears with RSSI < −120 dBm or SNR < −10 dB, the signal is at the noise floor — unreliable communication. If it doesn't appear at all, no packets are being received.

Test: bring both devices to within 100 feet of each other (no obstacles). If they communicate at that distance, it's a range/obstruction problem. If they still can't communicate at 100 feet, it's a configuration problem.

Problem: Intermittent message delivery

Check: Hop count

Messages requiring more hops have higher failure rates. Check your hop limit setting:

meshtastic --get lora.hop_limit

Default is 3. If messages are being dropped across long paths, try increasing to 5:

meshtastic --set lora.hop_limit 5

Check: Network congestion

In dense networks (20+ nodes), Long Fast preset can cause congestion. Symptoms: high message drop rate even with good RSSI, large delays. Solution: migrate to Medium Slow or Medium Fast preset. Requires coordination with all network participants — all nodes must change at the same time.

Check: Router node availability

If a critical router node goes offline, messages that depended on that path fail. Use Trace Route before and after to confirm the path change:

meshtastic --traceroute !nodeId

Problem: Poor range from a new repeater

1. Antenna connected? An unconnected antenna transmits into the PCB and can damage the radio front-end. Verify the antenna is finger-tight. Some boards have a separate BLE antenna and LoRa antenna — ensure both are connected.
2. Correct antenna type? Most boards use SMA or u.FL connectors. Verify your antenna has the correct connector type and is rated for 915 MHz. An 868 MHz antenna will work but at reduced efficiency.
3. TX power set correctly? Check that TX power hasn't been set to an unusually low value: meshtastic --get lora.tx_power
4. Obstructions: Even a metal enclosure, HVAC equipment, or tree canopy directly around the antenna can reduce range significantly. Test with the antenna in the clear before committing to a location.