Field Testing and Coverage Verification

Why Field Test?

Even the best RF prediction tools are only as good as their terrain models. Buildings, vegetation, and local obstructions can significantly degrade predicted coverage. Field testing confirms what the models predict — and reveals the surprises they miss.

Basic Field Test Procedure

1. Deploy the repeater at the proposed site, even temporarily on a tripod.
2. Walk or drive the coverage area with a second device (phone running the Meshtastic app, or a handheld node).
3. Record signal metrics at known locations: SNR (signal-to-noise ratio) and RSSI (received signal strength indicator).
4. Note locations where packets stop getting through — this defines your coverage boundary.
5. Compare results to your predicted coverage map and identify gaps or surprises.

Understanding SNR and RSSI for LoRa

RSSI is received signal power in dBm. Typical useful values for LoRa: −90 to −120 dBm. Below −120 dBm, reliability degrades rapidly.

SNR is signal-to-noise ratio in dB. LoRa's key advantage over conventional radios is its ability to decode packets at negative SNR values. At SF11 (Long Fast preset), packets typically decode down to −17.5 dB SNR.

Rule of thumb:

• SNR > 0 dB — strong signal.
• −5 to −10 dB — marginal but usable.
• Below −15 dB — at or near the noise floor; packet loss likely.

Reading Signal Data in Meshtastic

The Meshtastic app shows RSSI and SNR for each received packet in the message details view. This is real link-quality data from your actual deployment — use it as your primary signal source during field testing.

Recording a Coverage Map

Simple approach: note GPS coordinates alongside SNR and RSSI values in a spreadsheet while driving, then export the data to Google My Maps or another mapping tool.

Automated approach: enable the Meshtastic Range Test module (Config → Module → Range Test). It automatically logs positions with signal data to a CSV file as you walk or drive the area.

Visualisation: import the CSV into Google My Maps or QGIS to produce a signal-strength overlay map that you can compare directly against your predicted coverage.

What to Look For

• Expected coverage but no packets: interference, antenna issue, wrong modem preset, or an obstruction absent from the terrain model.
• Better-than-expected coverage: diffraction over a ridge, reflections from buildings or open water.
• Unexpected dead zones: metal structures, buildings with metal roofing, or terrain features not captured in SRTM data.

Iterating on the Design

If field testing reveals coverage gaps, consider: adding a second repeater as a relay node, increasing antenna height, or repositioning the existing repeater. A 10-metre increase in antenna height can eliminate a surprisingly large dead zone — elevation is often more valuable than additional TX power.