A Meshtastic node's first channel. It also determines the frequency slot the node transmits on.
Glossary
Short definitions of terms used across the guides, explainers and device pages.
Updated 29 Oct 2026
LoRa radio
- 868 MHz (EU_868)
The sub-GHz band used by UK and EU LoRa mesh, and the Meshtastic region named EU_868. As of IR 2030 v1.16, the 869.40-869.65 MHz sub-band allows 500 mW ERP at a 10% duty cycle; the other sub-bands in the 868 MHz range are lower power.
- 915 MHz (US_915)
The licence-exempt band used in the US and Canada and some other regions. Equipment tuned for it is not for UK use, where LoRa mesh runs on 868 MHz.
- Airtime
How long a packet occupies the channel. It rises sharply with spreading factor and packet size, and it is the scarce resource on a shared LoRa channel.
- Amateur (ham) radio licence
A personal operating licence needed to use amateur bands and higher power. Licensed networks such as AREDN and HAMNET require one, and amateur rules do not allow encrypting traffic to hide its meaning. No licence is needed for licence-exempt short range devices operating within their limits.
- Antenna gain
How much an antenna concentrates power in one direction compared with a reference, without creating any extra power. More gain means a narrower beam, which for an omnidirectional antenna is squeezed mostly in the vertical plane.
- Bandwidth (LoRa)
The width of the channel a LoRa chirp is spread across, typically 125, 250 or 500 kHz. Wider channels give faster data rates but lower sensitivity.
- Callsign
The unique identifier issued with an amateur radio licence, which operators must transmit to identify their stations.
- Channel utilisation
The share of time a channel is busy with transmissions, as reported by Meshtastic firmware and apps. High values mean more collisions and dropped packets.
- Chirp spread spectrum (CSS)
A technique where the transmitter sweeps its frequency up or down across the channel, and the receiver recognises the sweep pattern even when it is below the noise. It is the physical basis of LoRa's range.
- Coding rate (CR)
The forward-error-correction overhead added to each LoRa packet, written 4/5 to 4/8. More overhead recovers more corrupted bits at the cost of longer airtime.
- dBi / dBd
Antenna gain measured against an ideal isotropic radiator (dBi) or against a half-wave dipole (dBd). dBi equals dBd plus 2.15.
- dBm
Power on a logarithmic scale relative to 1 milliwatt: 0 dBm is 1 mW, 14 dBm is about 25 mW and 27 dBm is about 500 mW. Every 3 dB roughly doubles the power.
- Duty cycle
The maximum fraction of time a device may transmit in a band: 10% means up to 6 minutes in an hour. Rules like this share spectrum fairly between many users.
- EIRP (effective isotropic radiated power)
The same idea as ERP but referenced to an isotropic radiator, so EIRP is ERP plus 2.15 dB. Many regions, including those on 915 MHz, state their limits in EIRP.
- ERP (effective radiated power)
Transmitter output plus antenna gain, minus cable loss, referenced to a half-wave dipole. UK 868 MHz limits are stated in ERP, so a gain antenna counts towards the limit.
- Forward error correction (FEC)
Adding redundant bits to data so the receiver can repair some errors without asking for a resend. In LoRa, the coding rate controls how much is added.
- Free-space path loss (FSPL)
Signal weakening over distance in clear line of sight, which grows with the square of both distance and frequency. Real paths lose more to terrain, buildings and foliage.
- Fresnel zone
An ellipsoid-shaped volume around the straight line between two antennas. Obstructions inside it, especially the first zone, weaken the link even when the straight line is clear; a common rule of thumb is to keep about 60 percent of the first zone clear.
- ISM band
Radio spectrum set aside internationally for industrial, scientific and medical use, which licence-exempt devices may share.
- Line of sight (LoS)
A path between two antennas with nothing in the way. Microwave and 868 MHz links work best with it, though LoRa can sometimes work without it over short distances.
- Link budget
The sum of all gains and losses between a transmitter and receiver: transmit power and antenna gains against path loss, cable loss and the receiver's minimum sensitivity. If the budget stays positive with some margin, the link should work.
- Listen before talk (LBT)
A rule where the radio checks that the channel is idle before transmitting. In the UK's 869.40-869.65 MHz sub-band, IR 2030 v1.16 requires spectrum-access techniques per EN 300 220 (such as listen before talk) or, alternatively, a duty cycle of 10% or less.
- LoRa
A radio modulation from Semtech that spreads a signal across a wide band using chirps, trading data rate for range and tolerance of noise. It carries tens to a few thousand bits per second, enough for short messages but not web browsing.
- LoRaWAN
A separate, higher-layer protocol that runs over LoRa radios in a star layout, with devices talking to gateways that relay to a central server. Meshtastic, MeshCore and Reticulum use LoRa radios but do not use LoRaWAN.
- Noise floor
The background radio noise level in a given bandwidth. A signal normally needs to be near or above it to be received, except with spread-spectrum modes like LoRa.
- Preamble
The repeating lead-in sequence at the start of a LoRa packet that lets the receiver lock on before the data begins.
- Receiver sensitivity
The weakest signal a receiver can still decode. LoRa chips decode far below the noise floor at high spreading factors; Semtech quotes the SX1262 at around -148 dBm in its best case, so check the datasheet for the conditions.
- RSSI (received signal strength indicator)
The measured received power in dBm, usually shown as a negative number such as -110 dBm, where closer to zero is stronger. It says nothing about how much noise is present.
- SNR (signal-to-noise ratio)
Signal power compared with noise, in dB. LoRa can decode packets at negative SNR, meaning the signal is below the noise, which is why a weak RSSI with a healthy SNR can still work.
- Spreading factor
A LoRa radio setting that trades speed for reach: a higher spreading factor (up to 12 on SX126x chips) gives better sensitivity and range but a much lower data rate and longer time on air. Each step up roughly doubles airtime. Meshtastic's presets pair a spreading factor with a bandwidth.
- SRD (short range device) band
The European regulatory category for low-power licence-exempt devices, including the 863-870 MHz range that LoRa mesh radios use in the UK and EU.
- SX1262
Semtech's LoRa transceiver chip, used in many current mesh boards from makers such as Heltec, RAK and LilyGO. It outputs up to +22 dBm and succeeds the older SX127x family.
- Sync word
A value in the LoRa packet header that helps separate networks sharing a frequency, so radios set to a different sync word generally ignore each other.
MeshCore
- Companion (MeshCore)
The end-user MeshCore role, used with a chat app over Bluetooth, USB or Wi-Fi. A companion node does not repeat messages for others.
- MeshCore
An open-source LoRa mesh project for multi-hop packet routing, where nodes have fixed roles such as companion, repeater and room server. Companion nodes do not repeat messages for others.
- Repeater (MeshCore)
A dedicated MeshCore node that extends network coverage by relaying messages.
- Room server
A MeshCore node that acts as a simple bulletin-board server for shared posts.
Meshtastic
- Channel (Meshtastic)
A named group defined by a name and a key. Nodes on the same channel with the same key can read each other's messages, and a device can hold more than one channel, with one of them as the primary.
- Device role
A node's configured behaviour: CLIENT (normal), CLIENT_MUTE (does not rebroadcast), ROUTER (fixed infrastructure that rebroadcasts aggressively), REPEATER, TRACKER, SENSOR, TAK and others. A wrongly set ROUTER role is a common cause of congestion.
- Direct message (DM)
A message addressed to a single node rather than broadcast to everyone on a channel.
- Flooding
Forwarding a packet to all neighbours so it reaches every node. It is simple and robust but wasteful of airtime.
- Hop limit
In Meshtastic, the maximum number of times a message may be rebroadcast on its way through the mesh. It cannot be greater than 7, and the default is 3. High values add load because every extra hop uses more airtime.
- LongFast
The default Meshtastic preset, using spreading factor 11, 250 kHz bandwidth and coding rate 4/5. It balances range and speed, and most public meshes share it.
- LongModerate
A long-range preset with a lower data rate than LongFast, trading speed for range.
- Managed flooding
Meshtastic's routing approach: nodes rebroadcast the packets they hear, with logic that reduces redundant rebroadcasts by nodes that heard another node forward the same packet first.
- MediumFast / ShortFast
Faster, shorter-range presets suited to dense or urban meshes where airtime matters more than distance.
- Meshtastic
Open-source firmware and apps that turn cheap LoRa boards into a text-messaging mesh, with phones pairing over Bluetooth, Wi-Fi or USB. It is not an internet replacement.
- Modem preset
A named bundle of spreading factor, bandwidth and coding rate. In EU_868 the presets include LongFast (the default), LongModerate, MediumFast, MediumSlow, ShortFast and ShortSlow. Turbo variants (including LongTurbo) use 500 kHz bandwidth and are not available in EU_868.
- MQTT bridge
An optional Meshtastic feature that connects a node to the internet through MQTT, a lightweight messaging protocol, so that separate meshes can be linked to each other.
- Node ID / node number
The unique identifier of a Meshtastic device, derived from its hardware address.
- Primary channel
- PSK (pre-shared key)
A secret key that both ends already hold. Meshtastic channels are encrypted with AES using a PSK, and because the default key is publicly known, the default channel is effectively public.
- Region (Meshtastic)
A required Meshtastic setting that selects the legal frequency plan and power limits for where you are, for example EU_868 in the UK.
- Repeater (Meshtastic role)
A Meshtastic role that forwards traffic. Per Meshtastic's device-role table it is not shown in the Nodes list and has minimal overhead.
- Router (Meshtastic role)
A well-placed, fixed, powered node whose job is to extend coverage. The role is for sites on high ground, not for handheld users.
- TTL (time to live)
A counter on a packet that goes down at each hop so loops and endless forwarding stop. Meshtastic's hop limit is its form of this idea.
Networking
- ASN (autonomous system number)
A number identifying a network that routes in its own right on the internet.
- BGP
Border Gateway Protocol, the protocol networks use to tell each other which addresses they can reach.
- CGNAT (carrier-grade NAT)
An ISP technique that shares one public IPv4 address among many customers, which can block inbound connections to equipment behind it. That makes hosting services from a home or community node harder.
- ISP (internet service provider)
A company or organisation that provides internet connectivity. Some community networks operate as one, and some only relay traffic for members.
- IXP (internet exchange point)
A shared facility where networks meet to peer. Guifi.net has been connected to CATNIX since 2011, and Ninux has been a member of NaMeX since 2013.
- Latency
The delay a packet takes to cross a network. On LoRa, long airtime makes it a limiting factor for messaging.
- Net neutrality
The principle that traffic is carried without discrimination by source, destination or content.
- Peering
A direct agreement between networks to exchange traffic, often without payment.
- Store and forward
Keeping a message at an intermediate node until the recipient can be reached. LXMF propagation nodes work this way.
- Throughput
The data rate actually achieved, which for LoRa is usually bits to low kilobits per second.
- Transit
Paying an upstream network to carry your traffic to the rest of the internet.
Reticulum
- Announce
A signed broadcast by which a destination makes itself known and lets the network learn a path to it.
- cjdns
A separate encrypted IPv6 mesh routing system sometimes used by community networks; NYC Mesh began in 2012 as an experiment with it. It is not part of Reticulum.
- Destination
A Reticulum endpoint with a 128-bit address (a hash), reachable by packets that are encrypted to it.
- Identity (Reticulum)
A public/private keypair that proves who a Reticulum peer is. Every addressable thing in Reticulum is derived from one.
- Interface (Reticulum)
A configured link to a medium such as LoRa, TCP, UDP, serial or I2P. A single node can bridge several interfaces.
- LXMF (Lightweight Extensible Message Format)
The messaging layer on top of Reticulum used by Sideband and NomadNet, which supports store-and-forward delivery.
- NomadNet
A terminal-based messaging and page-hosting program for Reticulum that gives users text pages, like a small decentralised web.
- Propagation node
An LXMF node that stores messages for recipients who are not reachable at the time and delivers them later. When several exist on a network they peer with each other and synchronise messages.
- Reticulum
A cryptographic networking stack by Mark Qvist that can run over LoRa, serial, TCP, Wi-Fi, I2P and other media at once, with no central addressing.
- RNode
An open firmware and hardware design for LoRa radios, used as a Reticulum interface.
- Sideband
A Reticulum and LXMF messaging app for Android, Linux, macOS and Windows.
- Transport node
A Reticulum node that forwards traffic and path information for others. Ordinary nodes only talk for themselves, and transport mode is opt-in.
Wi-Fi and broadband mesh
- 802.11s
The IEEE amendment that defines Wi-Fi mesh at layer 2, with its own path-selection protocol. Some OpenWrt devices support it.
- AREDN
Amateur Radio Emergency Data Network, a Wi-Fi mesh for emergency communications run by licensed amateur radio operators.
- Babel
A distance-vector routing protocol designed to work on both wired and wireless links and to cope with unstable ones. It is standardised as RFC 8966.
- Backhaul
The higher-capacity links that carry aggregated traffic between access points and the wider network.
- BATMAN-adv
Short for Better Approach To Mobile Ad-hoc Networking, advanced: a Linux kernel module that builds the mesh at layer 2, so the whole mesh looks like one Ethernet switch to devices. Many Freifunk communities use it.
- BMX6 / BMX7
Routing daemons derived from the BATMAN lineage, used in some community networks.
- DFS (dynamic frequency selection)
A rule on some 5 GHz Wi-Fi channels that makes radios move off a channel when radar is detected. It can cause unexpected drops on rooftop links.
- Gateway (mesh)
A node that connects the mesh to another network, typically the internet. Without a gateway the mesh is an island.
- HAMNET
A European IP network run by licensed amateur radio operators.
- Last mile
The final connection from the network edge to the user's premises.
- Mesh routing protocol
Software that decides which neighbour to forward traffic through. Protocols used by community networks include BATMAN-adv, OLSR, Babel and BMX.
- Node
A single building or site on the network, sometimes holding several radios. Counting rules differ between networks, so node counts are not directly comparable.
- OLSR
Optimized Link State Routing, a proactive IP routing protocol in which nodes regularly share link information. It has been used by a number of community networks.
- Omnidirectional antenna
An antenna covering all horizontal directions, used for local coverage and on most LoRa nodes.
- OpenWrt
A Linux distribution for routers, and the base of most community-network firmware.
- OSPF
Open Shortest Path First, a link-state routing protocol. NYC Mesh's wiki describes it as carrying internal traffic inside the network.
- Pico peering agreement
A short, plain-language agreement under which each participant lets traffic cross their node for others. FunkFeuer is one network that uses it.
- PtMP (point-to-multipoint)
One access point, often with a sector antenna, serving several client radios.
- PtP (point-to-point)
A radio link between exactly two directional antennas, used for long, fast backhaul.
- Sector antenna
An antenna that covers a wedge, typically 60 to 120 degrees wide, so one site can serve several nearby nodes in a direction.
- Supernode
A well-connected, higher-capacity node that other nodes link into. The word is used differently by different networks, so check how a given network defines it.
- Uplink
The connection from a mesh or ISP towards the wider internet.
- Wireless mesh network
A network where nodes relay traffic for each other, so there is no single central point.