Technical details

Original Santa Clara (SmartNet) system info

This page describes the original hardware and software set up for monitoring the analog SmartNet-based city of Santa Clara 800 MHz radio system. Later work (2014-2016) was the digital Project 25 phase 2 SVRCS system which used the same foundation but with slightly different radio hardware (700 MHz), and vastly different software for digital voice decoding.


The original Super Trunking Scanner production backend used a USRP1 with a DBSRX2 daughterboard for radio reception. This photo shows that unit with some extra antennas installed for another daughterboard.

This all ran on a normal but beefy (for 2011) Linux box. A fair amount of CPU power is required to keep up with the decoding work.


The backend was a custom project built on top of GNU Radio to decode the control channel and drive audio logging handlers. It took the raw I/Q data arriving from the USRP (about 115 Mbps, 24 hours a day) and saved it to separate calls.

The frontend is a combination of HTML, CSS and Javascript which creates a web application in your browser. It uses AJAX for seamless updates.

Why this matters

Unlike ordinary scanners, this system receives all channels simultaneously and can record all of them in parallel if necessary. Even if multiple talkgroups are active -- police and fire, for example -- you'll still hear every call.

Would you like to know more?

The development of this project was documented in a series of posts. Read on for the details.