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34 lines
2.2 KiB
HTML
34 lines
2.2 KiB
HTML
<!DOCTYPE html>
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<html lang="en" dir="ltr">
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<head>
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<meta charset="UTF-8">
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<meta name="viewport" content="width=device-width, initial-scale=1.0">
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<title>How the Meshtastic Signal Meter Works</title>
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<link rel="stylesheet" href="../styles/docs.css">
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</head>
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<body data-page="signal-meter" data-locale="en">
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<pre class="markdown-content"># How the Meshtastic Signal Meter Works
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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.
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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.
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## 2. The Magic of LoRa: Hearing "Below the Noise Floor"
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For standard radios (like FM or WiFi), if the background noise is louder than the signal (a negative SNR), the receiver just hears static.
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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).
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Depending on which Meshtastic preset you are using (e.g., `LongFast` vs. `ShortFast`), 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.
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----|------|----------|---------|
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Good | 3 | SNR **above** the preset's `limit` | Signal is comfortably above the demodulation floor — healthy connection. |
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Fair | 2 | less than `5.5 dB` below the `limit` | Decodable, but getting close to the floor. |
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Bad | 1 | `5.5 dB` to `7.5 dB` below the `limit` | At the very edge of what the preset can recover. |
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None | 0 | more than `7.5 dB` below the `limit` | Below the floor — transmission lost to noise. |
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> **Note:** The fixed SNR thresholds you may have seen elsewhere (`-7 dB` / `-15 dB`) are now only used for coloring individual hops in traceroute results — not for the per-node signal meter described here.
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</pre>
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</body>
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