The GNU Radio software provides the framework and tools to build and run software radio or just general signal-processing applications. The GNU Radio applications themselves are generally known as "flowgraphs", which are a series of signal processing blocks connected together in software, thus describing a data flow. As with all software-defined radio systems, re-configurability is a key feature. Instead of using different radios designed for specific but disparate purposes, a single, general-purpose, radio can be used as the radio front-end, and the signal-processing software, handles the processing specific to the radio application.
We started out by building a simple audio signal generator and moved on to a full featured FM broadcast receiver. The hardware tuner is the inexpensive RTL2832U + R820T dongle available on eBay and other sources. With a frequency range of 24 – 1766 MHz it is fully 100% compatible with GNUradio and permits building devices across the ham bands.
The USB dongle from eBay Inside the RTL USB dongle
The dongle is actually manufactured for receiving TV broadcasts on Asian computers, but for us it means that a cheap $20 TV tuner USB dongle with the RTL2832U chip can be used as a software defined radio (SDR). This sort of capability would have cost hundreds or even thousands of dollars just a few years ago. The RTL-SDR is also often referred to as RTL2832U, DVB-T SDR, RTL dongle or the “$20 Software Defined Radio”.
Watch for an article in the next Communicator. In the meantime, here are three sites with additional information:
- For general RTL dongle news: http://rtl-sdr.com
- A signal hacker lady, very smart and she has interesting articles: http://windytan.com
- A YouTube video: https://www.youtube.com/watch?v=6nZIvueWDds