Using Multiple RTL-SDR’s to Capture a Trunking System

Using three RTL-SDR's to monitor a 6 MHz trunking system.

An RTL-SDR dongle has a maximum usable bandwidth of about 2.4 MHz which most often isn’t enough to capture an entire trunking system that may be spread out over a larger bandwidth. In order to get around this limitation Luke Brendt has been using three RTL-SDR dongles together to capture a trunking system in his area which is spread over 6 MHz of bandwidth.

Luke uses his own Trunk Recorder software and writes that he has modified it to support multiple SDR’s. His software has the following description:

Trunk Recorder is able to record the calls on a trunked radio system. It uses 1 or more Software Defined Radios (SDRs) to do. The SDRs capture large swatches of RF and then use software to process what was recieved. GNURadio is used to do this processing and provides lots of convienent RF blocks that can be pieced together to do complex RF processing. Right now it can only record one Trunked System at a time.

  • Trunk Recorder currently supports the following:
  • P25 & SmartNet Trunking Systems
  • SDRs that use the OsmoSDR source ( HackRF, RTL – TV Dongles, BladeRF, and more)
  • Ettus USRP
  • P25 Phase 1 & Analog voice


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