SDR Superiority

A Detailed Look at More Emergency Preparedness Applications of Software-Defined Radio

- W.Dean Freeman

In Issue 45, I introduced Software-Defined Radios (SDRs) using the popular RTL-SDR dongle and the open source Garx software for receiving a variety of analog voice transmissions on multiple different bands for simple gathering of signals intelligence (SIGINT) and news. However, SDRs aren't necessary to do most of that work. My Yaesu VX-6R handheld transceiver, for instance, is capable of receiving high frequency (HF) bands for shortwave listening, as well as AM air bands. SDRs really shine as a result of:

• Their relatively inexpensive price point
• Their flexibility when paired with the appropriate software

That flexibility is especially evident when dealing with the wide array of digital communications that they're capable of receiving and decoding. The low cost of the hardware and the zero cost of most of the software is what makes them such an excellent tool in the toolbox for monitoring and analyzing the RF signal cloud around us on a daily basis.

In this issue, I'll explore some additional ways in which software-defined radios help level the playing field with amateur SIGINT, specifically:

• Monitoring and tracking aircraft via ADS-B
• Monitoring and decoding trunked and digital voice communications
• Coupling SDRs with Android devices

Aircraft Monitoring with ADS-B

Modern air traffic control doesn't really rely solely on radar. Instead, air traffic control systems make use of advanced digital transponders, which report on various relevant aspects of the flight and its position. This information is provided by a system called Automatic Dependent Surveillance-Broadcast (ADS-B).

ADS-B data packets are broadcasted periodically by the transmitter on equipped aircraft and include data such as: