POCSAG Pager Message Decoding

~60 minBeginner

Decode unencrypted POCSAG pager traffic in real time using an RTL-SDR and multimon-ng — from signal hunt to live message display.

Prerequisites
Gather these before starting

Hardware

  • •RTL-SDR dongle (any model)
  • •Antenna for 150–160 MHz (whip or discone)
  • •Computer with USB port
  • •Location near paging infrastructure (urban areas best)

Software / Knowledge

  • •multimon-ng (installed in Step 4)
  • •rtl-sdr tools (rtl_fm command)
  • •SDR++ or GQRX for frequency hunting
  • •Comfort with command line
Step 1 of 617% complete
Step 110 min
Understanding POCSAG Protocol

POCSAG (Post Office Code Standardisation Advisory Group) is a one-way paging protocol developed in 1978 and still in widespread use. It transmits messages using FSK (frequency-shift keying) and is completely unencrypted — making it trivial to decode with an SDR.

Protocol parameters

Modulation2-FSK (Binary FSK)
Baud rates512, 1200, 2400 baud
Frequency deviation±4.5 kHz
Message typesNumeric, Alphanumeric, Tone-only
Address space2,097,152 addresses (21-bit RIC)
Preamble576 alternating bits for sync
Error detectionBCH(31,21) per codeword

Common use cases in 2025

  • Hospitals: Doctor on-call alerts, code blue, critical lab results
  • Fire services: Station alerting and incident dispatch
  • Electric/gas utilities: Field crew dispatch, outage alerts
  • Industrial: Process alarms, maintenance alerts
  • Retail: Customer-facing restaurant pagers at 433 MHz
  • Emergency services: Many countries' national alerting systems

Legal reminder

Receiving pager transmissions is legal in most jurisdictions (passive reception). However, intercepting and acting on private communications may be restricted. Always check local laws and use this knowledge for educational and research purposes only.

POCSAG is still widely used by hospitals, fire departments, and utility companies in 2025 — many of whom haven't encrypted their paging systems.

Understanding POCSAG Protocol