📖 Glossary — Meshtastic terms in a nutshell¶

SNR (signal-to-noise ratio, dB)

How far the signal sits above the noise. Thanks to spreading, LoRa decodes signals below the noise floor — depending on the modem preset down to about −7 dB (short presets) or −20 dB (Long Slow). Rule of thumb: > 5 dB very good, around 0 dB solid, clearly negative = marginal.

RSSI (received signal strength indicator, dBm)

Absolute reception level. Typical LoRa values range from ≈ −60 dBm (very close/strong) to ≈ −125 dBm (reception limit). Unlike SNR it is independent of the noise level — both together tell the story.

Noise floor (dBm)

Base noise at the receiver (environmental interference + receiver noise). Approximation: RSSI ≈ noise floor + SNR. Newer firmware reports it in LocalStats.

Hop

One forward through a relay node (Meshtastic counting: direct = 0 hops). Every hop adds latency and airtime; the hop limit (default 3, max. 7) bounds a message's reach. Not to be confused with the number of radio legs:

Link	Hops (relay forwards)	Radio legs
A → B	0	1
A → R1 → B	1	2
A → R1 → R2 → B	2	3

Airtime

The time a transmission occupies the radio channel. A shared resource: the longer the modem preset and the more packets/hops, the less capacity remains for everyone else.

Channel utilization (%)

Share of time the channel is busy (own + foreign transmissions). Persistently above ~25–40 % gets critical — packets collide and get lost.

Modem preset (e.g. Short Slow, Long Fast)

Combination of bandwidth and spreading factor. "Short" presets = higher data rate, shorter airtime, less range; "long" presets the other way around. All nodes of a mesh must use the same preset.

MQTT

Internet bridge between mesh islands: gateways lift packets onto a broker and back. Great for reach — but a "neighbor via MQTT" is not a radio neighbor. That's why the client labels MQTT segments separately.

Direct neighbors / real RF neighbors

Nodes provably heard directly over radio (0 hops, no MQTT) — proven by own direct reception, traceroute hop pairs or NeighborInfo packets.

NeighborInfo

Packet type with which a node itself reports whom it hears directly — one of the three evidence sources for real RF neighbors.

Traceroute

Diagnostic request that records the path to a target node: every station adds itself with per-hop SNR (outbound and return).

PKI (public key infrastructure)

Key pairs (X25519) for encrypted direct messages and admin access. The client decrypts PKI DMs client-side (AES-256-CCM) and manages known public keys in node_keys.csv.

NodeDB

A device's node database: every node ever heard, with names, positions, telemetry snapshots. The client loads it on connect and enriches it with its own telemetry history.

LocalStats

Statistics telemetry of newer firmware: noise floor, RX total/bad/duplicates, TX/relay counters, nodes online. The basis for rates (packets/h) and the radio overlays.

precision_bits (position precision)

Meshtastic can deliberately coarsen transmitted positions (e.g. 13 bits ≈ ±2.9 km). The client displays and accounts for this blur (for instance in position estimation).

Fresnel zone

Ellipsoid-shaped space around a radio link's line of sight that must stay largely clear for clean reception (rule of thumb: 60 % of the 1st zone). Terrain poking into it causes extra loss — exactly what the client's elevation profile shows.