Taking scanning to the next level using distributed RTLSDR receivers & open source software
Cyberspectrum #23 @ DEF CON 2018
August 9th, 2018
Digital scanners especially those capable of newer digital protocols are pricey.
## P25 Phase II scanner - $400 ## RTLSDR dongle - $25
Traditional scanners can only receive one transmission at a time. But large trunked systems could have activity on multiple channels at once, forcing users to miss out.
As agencies continue to adopt radios that use digital modulation. Many scanner enthusiasts are unable or unwilling to obtaing digital scanners due to cost and complexity.
They compensate for some shortcomings and allow portability, but are still limited by the constraints of hardware scanners.
Using SDR & open source technologies, we can make scanning easier and more user-friendly. OC Radio Live is a website that I created to use SDR to stream transmissions from local radio systems.
OC Radio Live features:
Thanks to trunk-recorder we can record:
These capabilities allow us to record the following types of systems using the site: ### Aging 500 MHz Motorola Type II TRS ### New State & County 700 MHz P25 Phase II systems ### Analog VHF and UHF conventional channels
Hardware scanners only offer a simple lockout and various banks of channels. OC Radio Live has data on invididual channels, entire radio systems and custom scan lists for regions and types of radio traffic.
Toms River, NJ (700, 460 and 155 MHz) (outside)
Lacey, NJ (500 MHz) (inside)
trunk-recorder uses JSON syntax for defining systems and SDRs. Some examples of the systems I defined are on Github
Scanning the NJICS 700 MHz system
The frontend is hosted on a simple Ubuntu 16.04 VPS on a cloud hosting provider.
* trunk-recorder reads in the JSON configuration file for the system(s) and allocates recorders on multiple RF channels within the SDR’s bandwidth.
* A bash script passes the transmissions along with JSON metadata to the frontend server, where it is written to a database.
* The transmissions are uploaded to Amazon S3 for storage and deleted from the frontend.
* Users can play live transmissions & access archives on the frontend website.
SDR can break down cost & complexity barriers to monitoring public safety radio systems. SDR combined with web services can allow receiving setups previously not possible with past hardware radios.