If you read the pages of this blog with interest, you probably are a member of G-QRP. If not, I heartily recommend that you join.
SPRAT's editor George, g3rjv, kindly gave me permission to make a local copy of the article available through this website - you can download such a copy here.
This page presents some resources which support that article, and other publications and presentations arising from it.
The resources include software for the Arduino controller and schematics to show how to assemble an RF generator using two AD9850 DDS Modules.
The present system - the simplest possible - demonstrates the core principles discussed in the SPRAT article in a simple RF generator for HF applications.
This system uses the schematic shown below, which shows two DDS Modules interfaced to the Arduino using "soft SPI".
Note that the modules share their DATA and RESET lines, to save on Arduino I/O resources.
The LCD unit is assumed to be that available from Kanga UK, for which a library is available from this page. Note that other displays may not work with this library - experimenters using other displays must provide their own library.
The Arduino sketch for the Double_DDS system is available at this github repository.
I have just noticed (17.8.2014) an error in the schematic shown as Figure 2 of the article, concerning the wiring of the transformer. This is corrected in the version below...
Further examples and applications will be posted here as they become available for public disclosure.
...-.- de m0xpd