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68 lines
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HTML
68 lines
5.3 KiB
HTML
<!DOCTYPE html>
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<html lang="pl-rPL" 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="pl-rPL">
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<pre class="markdown-content"># How the Meshtastic Signal Meter Works
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The Meshtastic signal meter — the bars or status color next to a node — is calculated differently from the bars on a cell phone or Wi-Fi router. This page explains what it measures and why the same reading can mean something different on another preset.
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## RSSI and SNR
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Every time the LoRa radio receives a message, it reports two measurements:
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- **RSSI (Received Signal Strength Indicator)** — the raw power hitting the antenna.
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- **SNR (Signal-to-Noise Ratio)** — how far the signal stands above the background noise.
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> 💡 **Tip:** Think of RSSI as how loud a friend is talking and SNR as how easily you can pick their voice out of the noise in the room. A friend shouting at a rock concert can be loud (high RSSI) yet unintelligible (bad SNR), while a whisper in a quiet library is faint (low RSSI) yet perfectly clear (great SNR).
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## Decoding Below the Noise Floor
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Standard radios such as FM or Wi-Fi lose a signal to static once the background noise is louder than it (a negative SNR). LoRa's spread spectrum modulation lets the radio pull a signal out of the noise even when the noise is louder, so negative SNR values are common and expected in Meshtastic — for example, −10 dB means the signal is 10 decibels weaker than the background noise.
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Each modem preset has an SNR limit: the lowest SNR at which that preset can still decode a message. Slower presets tolerate a weaker, noisier signal (a more negative limit, longer range); faster presets need a stronger signal (a less negative limit, shorter range).
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## Rating Signal Quality
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The app rates signal quality (None, Bad, Fair, or Good) from SNR relative to the active preset's SNR limit. When RSSI and a noise-floor reading are both available, it also rates the difference between them against that limit and uses the worse rating. Otherwise, it uses SNR alone.
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Because the rating is relative to the preset, the same SNR rates differently on different presets. An SNR of −16 dB rates Good on Long Fast (SNR limit −17.5 dB) but None on Short Fast (SNR limit −7.5 dB). Let `limit` be the active preset's SNR limit:
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Level | Bars | Criteria | Meaning |
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------------- | ---- | -------------------------------------------------------------- | --------------------------------------------------------------------------------------------------- |
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dobry | Full | SNR above `limit` | Comfortably above the demodulation floor — a healthy connection. |
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wystarczający | 3 | less than 5.5 dB below `limit` | Decodable, but approaching the floor. |
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słaby | 2 | 5.5 dB to 7.5 dB below `limit` | At the edge of what the preset can recover. |
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Brak | 1 | more than 7.5 dB below `limit` | Far below the preset's floor; further packets from this node are likely to be lost. |
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The icon never goes blank, so count the bars carefully: a single bar means None, not a weak but usable link, and Good is a solid wedge rather than a set of bars. A gray three-bar icon labeled Unknown is a different state again — the packet carried no SNR measurement at all, which is not the same as measuring one and finding it too weak.
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> ℹ️ **Note:** Traceroute and neighbor-info SNR colors use the active preset's limits too. RSSI text has separate strength colors: green above −115 dBm, yellow above −120 dBm, orange above −126 dBm, and red at or below −126 dBm.
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## Diagnosing Local Interference
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A great RSSI paired with a one- or two-bar rating (None or Bad) points to local interference, not distance. A cheap power supply, a noisy computer, or a nearby transmitter can create enough static to drown out an otherwise strong signal.
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## Where Signal Information Appears
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In the app, signal data appears in several places:
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- **Node list** — a signal-bars icon, shown only for nodes your radio heard directly. A node reached through a relay shows its hop count instead, because the SNR your radio measured describes the last hop, not the whole path
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- **Node detail** — SNR, RSSI, and the quality word in the **Details** card at the top of the screen
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- **Traceroute** — per-hop signal quality for each relay node
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- **Signal Quality** — historical SNR and RSSI data in the metrics charts
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## Related Topics
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- [Nodes](nodes) — where signal bars appear in the node list
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- [Node Metrics](node-metrics) — SNR/RSSI history and the per-node signal quality reference
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- [Settings — Radio & User](settings-radio-user) — modem presets and their SNR limits
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</pre>
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</body>
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</html> |