February 2013

DDS Sine Sweeper

DDS Sine SweeperIt's about time for some hardware, so here is the DDS Sine Sweeper, a sine source which outputs a sine wave from 1Hz-40MHz.  It's cheap and easy to build and all the plans and software are freely available.

From time to time I found myself needing  a separate signal generator.  In the back of my head I was thinking of just something simple but I also wanted to play about with DDS (Direct Digital Synthesis), a method of creating a waveform digitally.  This allows precise control over the frequency from a microcontroller, allowing you to set the frequency and even jump to another very quickly.  Although it does have drawbacks the simplicity was a winner for me.

RTLSDR Scanner

Screenshot 1

Last year while developing Linux drivers for digital TV, Antti Palosaar noticed a hidden debug mode, which allowed you to sample relatively large chunks of radio spectrum.  Thanks to this the RTL-SDR library was born and Software Defined Radio was available on the cheap, after all these dongles tend to cost less than £20.

A little while ago I uploaded my contribution to this, a GUI called RTLSDR Scanner, to GitHub.