I wrote Trunk Recorder because I was curious about what my local fire station was up to and I put together the original version of OpenMHz because I figured other people might want to listen to the recordings too.
The latest version of this site makes it easy for other people running Trunk Recorder to share their recordings. I am hoping that making it easier to listen to what our local fire, police and EMS have to go through everyday will lead to a greater appreciation for all the work they do, which goes largely unseen.
The audio from each system is archived for 30 days, so you can go back and listen to events you may have missed.
Github: https://github.com/openmhz
Trunk Recorder is able to record the calls on trunked and conventional radio systems. It uses 1 or more Software Defined Radios (SDRs) to do this. The SDRs capture large swathes of RF and then use software to process what was received. GNU Radio is used to do this processing because it provides lots of convenient RF blocks that can be pieced together to allow for complex RF processing. The libraries from the amazing OP25 project are used for a lot of the P25 functionality. Multiple radio systems can be recorded at the same time.
Trunk Recorder currently supports the following:
- Trunked P25 & SmartNet Systems
- Conventional P25 & analog systems, where each group has a dedicated RF channel
- P25 Phase 1, P25 Phase 2 & Analog voice channels
Trunk Recorder is able to record the calls on trunked and conventional radio systems. It uses 1 or more Software Defined Radios (SDRs) to do this. The SDRs capture large swathes of RF and then use software to process what was received. GNURadio is used to do this processing because it provides lots of convenient RF blocks that can be pieced together to allow for complex RF processing. The libraries from the amazing OP25 project are used for a lot of the P25 functionality. Multiple radio systems can be recorded at the same time.
Trunk Recorder currently supports the following:
- Trunked P25 & SmartNet Systems
- Conventional P25 & analog systems, where each group has a dedicated RF channel
- P25 Phase 1, P25 Phase 2 & Analog voice channels
SDRs supported
- RTL-SDR dongles
- HackRF
- Ettus USRP B200, B210, B205
- BladeRF
- Airspy
Turbine is the SDR software for NoraSector. It's designed to capture and stream all frequencies in a trunked radio system. It is capable of decoding multiple systems concurrently, even different system types, provided they all fall within the same sample bandwidth generated by the radio and there's enough CPU available.
It's built with the expectation that it uses a single SDR that is able to capture the bandwidth containing all frequencies in the system.
All audio is encoded using the Opus codec for compatibility with WebRTC and output over UDP.
Designed for big-bore SDRs, like the HackRF. You won't get an RTL-SDR working with this (even though I tagged it with that to make it easier to find).