As a club project we have decided to build the Elektor SDR radio from the May 2007 issue. The original article may be downloaded free of charge from the Elektor Web site here:-

Software-defined-radio.Article

The receiver is a base-band conversion type receiver using a master oscillator running 4xRX frequency. This can then be divided by 4 to produce two 90 degree out of phase signals. These are then mixed with the RF from the Antenna to produce two separate I and Q signals which are fed into the stereo line inputs of a standard sound card.

The receiver is controlled from a USB port on the computer

The construction is fairly straight forward apart from two surface mount chips, which the club can arrange to have fitted professionally.

Here is one members board with the surface mount chips in place (click for larger image) :-

The board can be used with a number of "soft radio" programs. (Click for larger images)

These include the G8JCF software :-

and the "Winradio" software

The radio performs very well, typically delivery about 40db of unwanted sideband suppression although performance does fall off towards the higher frequencies, and investigations are about to start to see if a pre-amplifier helps.