Field Guide · protocol

Also known as: Wireless M-Bus, wM-Bus, wireless Meter-Bus

Wireless M-Bus (wM-Bus) is the radio variant of the European Meter-Bus standard, used to read water, gas, heat, and electricity utility meters without a wired connection.1 Defined in the EN 13757 family (the radio layer is EN 13757-4), it lets a meter periodically transmit its reading over short-range sub-GHz radio to a fixed collector or a walk-by/drive-by reader — the backbone of automatic meter reading (AMR) across much of Europe. It uses simple FSK modulation, and its frames are readily received with ordinary SDR hardware.

water gas heat collector meters push short 868 MHz FSK bursts — no request needed
Wireless M-Bus meters push brief FSK bursts to a collector or drive-by reader, typically at 868 MHz.

Overview

A wM-Bus meter is usually the talker: it wakes on a schedule, sends a short frame containing its identity and consumption data, and returns to deep sleep to preserve its battery. The counterpart — a fixed concentrator or a technician’s mobile reader — listens and logs. Frames may be sent in the clear or encrypted (commonly AES-128), depending on the utility’s configuration.

Technical characteristics

Property Value
Standard EN 13757-4 (radio) within the M-Bus family
Bands 868 MHz (primary); also 169 MHz and 433 MHz
Modulation FSK / GFSK, rate depends on mode
Modes S (stationary), T (frequent transmit), C (compact), N (169 MHz), F (433 MHz)
Direction Meter-to-collector primary; some bidirectional
Security Optional AES-128 encryption of payload

The various letter modes trade data rate, band, and duty cycle to fit different meter types and reading strategies, from occasional walk-by to fixed-network collection.

History

Wired M-Bus (EN 13757-2/-3) came first for cabled meter buses; the wireless layer was added as EN 13757-4 to serve meters where running cable is impractical.2 It has been widely deployed as European utilities rolled out smart and automatic metering, and the OMS (Open Metering System) profile builds on it for interoperability.

Deployment

wM-Bus is common across European water, gas, heat, and electricity metering. Its short, infrequent bursts and long battery life make it a natural fit for meters buried in basements and pits, complementing cellular LPWANs like NB-IoT that some newer meters use instead.

Decoding it with GopherTrunk

GopherTrunk does not decode wireless M-Bus — it is a trunked land-mobile voice scanner, and metering telemetry is outside its scope. However, wM-Bus is very much receivable with general SDR tools: an RTL-SDR or similar software-defined radio tuned to 868 MHz, paired with community decoders (for example rtl_433 or wmbusmeters), will pull out meter frames, and readings decode fully when the frame is unencrypted or the key is known. That workflow just lives in those tools, not in GopherTrunk.

Sources

  1. Meter-Bus — Wikipedia, for the M-Bus standard family and its metering role. ↩

  2. Wireless Meter-Bus — Wikipedia, for the EN 13757-4 radio layer, 868 MHz operation, and mode structure. ↩

See also