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title: How the Meshtastic Signal Meter Works

parent: User Guide

nav_order: 15

last_updated: 2026-07-08

description: How the signal meter rates quality from SNR relative to the LoRa modem preset — spread spectrum, presets, and what the bars really mean.

aliases:

• signal

• signal-meter

• snr

• rssi

The Meshtastic signal meter — the familiar bars or status color in the app — is calculated very differently than the "bars" on a traditional cell phone or WiFi router.

Most consumer devices simply measure how "loud" a signal is. However, because Meshtastic uses LoRa (Long Range) technology, its signal meter measures how clear the signal is, relative to the specific settings your mesh is using.

2. It's built on top of a software defined radio platform called LoRa, enabling inexpensive radios (based on popular chips like the ESP32, nRF52, and RP2040) to operate as long range, low power, and secure communicators.

3. Common hardware includes devices like the RAK WisBlock series, T-Beam, Heltec, and LilyGo boards.

4. Meshtastic supports communication over several radio channels, allowing you to separate traffic or experiment with different settings. You can configure parameters like the spreading factor, bandwidth, and coding rate to optimize for range, data rate, and reliability. These settings are often referred to as radio profiles, with common examples being "Long Fast" or "Mid Slow".

5. Besides LoRa, Meshtastic devices can also communicate using BLE for short-range communication with smartphones and other devices.

6. Meshtastic devices can be configured using a variety of methods, including:

• A mobile app (available for Android and iOS)

• A web-based interface

• A CLI

• An API

7. Meshtastic can also be integrated with other systems using protocols like MQTT.

8. You can extend the functionality of Meshtastic devices by writing your own firmware or connecting external sensors and devices using the GPIO, USB, UART, SPI, and I2C interfaces.

9. Meshtastic devices can be powered by batteries, USB, or other power sources.

10. Meshtastic supports Over-The-Air (OTA) firmware updates via LoRa, WiFi or Bluetooth.

11. Meshtastic allows for end-to-end encryption of messages.

12. Meshtastic devices can act as repeaters, extending the range of the network. The Two Metrics: "Loudness" vs. "Clarity"

Every time the LoRa radio chip receives a message, it reports two measurements:

• RSSI (Received Signal Strength Indicator): The loudness of the raw power hitting your antenna.

• SNR (Signal-to-Noise Ratio): The clarity of the signal compared to the background static.

│ 💡 Tip: Here's an analogy — imagine you are trying to hear a friend talking to you. - RSSI is how

│ loud their voice is. - The Noise Floor is the background noise in the room (air conditioning,

│ other people talking, traffic). - SNR is how easily you can distinguish your friend's voice from

│ the background noise.

If your friend shouts at you at a deafening rock concert, the signal is incredibly loud (High RSSI), but you still can't understand them because the background noise is louder (Bad SNR). Conversely, if your friend whispers to you in a dead-silent library, the signal is very weak (Low RSSI), but you can understand them perfectly (Great SNR).

For standard radios (like FM or WiFi), if the background noise is louder than the signal (a negative SNR), the receiver just hears static.

LoRa is special. It uses "Spread Spectrum" modulation, which allows the radio to mathematically pull a signal out of the air even when it is buried deep underneath the background noise. This is why you will frequently see negative SNR numbers in Meshtastic (e.g., -10 dB, which means the signal is 10 decibels weaker than the background static).

Depending on which Meshtastic preset you are using (e.g., T383838LongFast vs. T383838ShortFast), the radio has a specific SNR Limit — the absolute maximum amount of noise it can tolerate before the message is completely lost to the static.

The app rates your signal quality (None, Bad, Fair, or Good) from SNR alone, measured relative to the preset's SNR Limit — the demodulation floor described above. It deliberately does not factor RSSI into the rating: without the local noise floor, RSSI cannot tell you whether a signal is actually decodable, so SNR-versus-the-preset-limit is the meaningful measure. (RSSI is still displayed to you elsewhere.)

Because the rating is relative to the preset limit, the same SNR can rate differently on different presets — T383838-15 dB is healthy on T383838LongSlow but unusable on T383838ShortFast. Letting T383838limit be the active preset's SNR Limit, here is how the app picks the bars (or color):

│ 不良 │ 1. Overview│ │ │

└───────┴─────────────────┴──────────────────────────────────┴─────────────────────────────────────┘

Meshtastic is a project that allows you to use inexpensive LoRa radios as a long range, off-grid, decentralized communication platform. These radios, combined with readily available and very affordable microcontrollers like the ESP32, nRF52, and RP2040, create a network that can be used to send text messages, share locations, and more without relying on cellular or WiFi infrastructure. It's perfect for hiking, camping, or any situation where you need to stay connected beyond the reach of traditional networks.

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• T-Beam: A popular board with ESP32, LoRa, and GPS.

• Heltec WiFi LoRa 32: Another popular ESP32-based board with LoRa.

• LilyGo Boards: LilyGo offers a variety of ESP32 and nRF52 based boards with LoRa.

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• Meshtastic Firmware: The core software that runs on the microcontrollers.

• Meshtastic Mobile App: For configuring and interacting with the devices. Available on Android and iOS.

• CLI (Command Line Interface): For advanced configuration and debugging.

• API (Application Programming Interface): For integrating Meshtastic with other applications.

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• Region Settings: Configure the correct region settings for your location.

• Channel Settings: Choose a channel or create a custom channel.

• Encryption: Enable encryption for secure communication.

• Power Settings: Adjust power settings to optimize battery life.

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• Hiking and Camping: Stay connected with your group in areas without cellular coverage.

• Emergency Communication: Provide a backup communication system in case of emergencies.

• Disaster Relief: Establish communication networks in areas affected by disasters.

• Rural Communication: Connect communities in remote areas.

• IoT Applications: Use Meshtastic for various IoT applications that require long-range communication.

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Tff7b72* **Meshtastic Website:** [https://meshtastic.org/](https://meshtastic.org/)

Tff7b72* **Meshtastic Documentation:** [https://meshtastic.org/docs/](https://meshtastic.org/docs/)

Tff7b72* **Meshtastic Forums:** [https://meshtastic.discourse.group/](https://meshtastic.discourse.group/)

Meshtastic 是一個專案，讓你可以使用便宜的 LoRa 無線電作為長距離、離線、去中心化的通訊平台。這些無線電，結合了容易取得且非常實惠的微控制器，像是 ESP32、nRF52 和 RP2040，創建了一個網路，可以用來傳送簡訊、分享位置等等，而不需要依賴行動網路或 WiFi 基礎設施。它非常適合健行、露營，或任何你需要保持連線，但又超出傳統網路覆蓋範圍的情況。

2) 主要組件

• LoRa 無線電: 提供長距離通訊能力。 RAK Wireless 模組是一個很受歡迎的選擇。

• 微控制器: 運作的大腦。 ESP32、nRF52 和 RP2040 因為它們的低成本和功能而被廣泛使用。

• GPS (可選): 用於位置分享。 許多裝置，像是 T-Beam，都有內建 GPS。

• 電池 (可選): 用於攜帶型使用。

• 外殼 (可選): 保護硬體。

3) 熱門裝置

• T-Beam: 一個受歡迎的板子，具有 ESP32、LoRa 和 GPS。

• Heltec WiFi LoRa 32: 另一個受歡迎的基於 ESP32 的板子，具有 LoRa。

• LilyGo Boards: LilyGo 提供各種基於 ESP32 和 nRF52 的板子，具有 LoRa。

4) 功能

• 簡訊傳輸: 透過 LoRa 網路傳送和接收簡訊。

• 位置分享: 與網路上其他使用者分享你的位置 (需要 GPS)。

• 加密: 可以加密訊息以保護隱私。

• 網狀網路: 網路會自動透過其他節點路由訊息，以到達目的地。

• 離線通訊: 不需要行動網路或 WiFi。

• 頻道設定: 客製化不同地區和使用案例的頻道設定 (Long Fast、Mid Slow 等)。

5) 軟體與 Firmware

• Meshtastic Firmware: 在微控制器上執行的核心軟體。

• Meshtastic Mobile App: 用於配置和與裝置互動。 可在 Android 和 iOS 上使用。

• CLI (Command Line Interface): 用於進階配置和除錯。

• API (Application Programming Interface): 用於將 Meshtastic 與其他應用程式整合。

6) 硬體設定

• 刷入 Firmware: 你需要將 Meshtastic firmware 刷入你的微控制器。 這通常是使用 USB 連線和刷入工具來完成的。

• 連接週邊設備: 將 LoRa 無線電和任何其他週邊設備 (GPS、電池) 連接到微控制器。

• 天線: 將適當的天線連接到 LoRa 無線電。

7) 配置

• 區域設定: 為你的位置配置正確的區域設定。

• 頻道設定: 選擇一個頻道或創建一個自定義頻道。

• 加密: 啟用加密以進行安全通訊。

• 電源設定: 調整電源設定以優化電池壽命。

8) 技術細節

• LoRa 調變: 使用 LoRa 調變進行長距離通訊。

• 頻率範圍: 根據地區在不同的頻率範圍上運作 (例如，北美為 915 MHz，歐洲為 868 MHz)。

• 微控制器介面: 使用各種介面在微控制器和週邊設備之間進行通訊，包括 GPIO、USB、UART、SPI 和 I2C。

• BLE (Bluetooth Low Energy): 用於初始配置和與行動應用程式的通訊。

• WiFi: 某些裝置支援 WiFi 用於 OTA (Over-The-Air) firmware 更新。

• MQTT: 支援 MQTT 用於與其他系統整合。

9) 使用案例

• 健行和露營: 在沒有行動網路覆蓋的地區與你的團隊保持聯繫。

• 緊急通訊: 在緊急情況下提供備份通訊系統。

• 災害救援: 在受災害影響的地區建立通訊網路。

• 農村通訊: 連接偏遠地區的社群。

• IoT 應用: 將 Meshtastic 用於各種需要長距離通訊的 IoT 應用。

10) 資源

• Meshtastic Website: https://meshtastic.org/

• Meshtastic Documentation: https://meshtastic.org/docs/

• Meshtastic Forums: https://meshtastic.discourse.group/ | T3838385.5 dB to T3838387.5 dB below the T383838limit | At the very edge of what the preset can recover. |

| 無 | 0 | more than T3838387.5 dB below the T383838limit | Below the floor — transmission lost to noise. |

│ Note: The fixed SNR thresholds you may have seen elsewhere (T383838-7 dB / T383838-15 dB) are now only used for

│ coloring individual hops in traceroute results — not for the per-node signal meter described

│ here.

Because Meshtastic's meter acts as a "Clarity Meter", it behaves differently than what most people expect:

│ 💡 Tip: Don't panic over low RSSI. You might see a seemingly terrible RSSI value like T383838-118 dBm.

│ On a cell phone, you would have zero bars. But if you have an SNR of T383838+2 dB, Meshtastic will still

│ show a strong signal! The library is quiet, so the whisper is heard perfectly.

│ ⚠️ Warning: Watch out for local noise. If you hook up a massive antenna and see a great RSSI

│ (e.g., T383838-90 dBm) but your signal meter is only showing 1 Bar (Bad), you have a problem. It means

│ you have local interference — perhaps a cheap power supply, a noisy computer, or a nearby radio

│ tower — creating so much static that it is drowning out your mesh.

In the app, signal data is shown in several places:

• Node list — signal bars icon next to each node

• Node detail — SNR, RSSI, and signal quality in the device metrics section

• Traceroute — per-hop signal quality for each relay node

• Signal metrics — historical SNR and RSSI data in the metrics charts

!Node entry showing SNR, RSSI values and colored signal bars

• Nodes — where signal bars appear in the node list

• Node Metrics — SNR/RSSI history and the per-node signal quality reference

• Settings — Radio & User — modem presets and their SNR limits