The Direct Digital Synthesis (DDS) Unit described in this document is based on the Analog Devices AD9951/54 family chips featuring advanced technology, high speed 14 bit Digital to Analog Converter, capable of generating a frequency-agile analog output sinusoidal waveform at up to 200 MHz with a fine tuning resolution of 32 bits.

The Unit consists of a 2-layer pcb providing maximum flexibility in a minimum size, it includes room and facilities for:

the 3,3 Volt Digital Vdd regulator, the 1,8 Volt Analog Vdd regulator, Quartz or On Board / External Oscillator,  Low-Pass Filtering and a Wide-Band linear Amplifier. The Unit can be interfaced to a micro based controller trough a suitable 6 pin connector.

The DDS Unit Circuit Diagram is drawn on Fig. 1, while Fig. 2 shows the actual Printed Circuit Board Top Layer.

This Project has been developed thank to the strictly collaborated work of i0CG, Giuliano and i0GLU, Giancarlo.

Giancarlo prototype (not yet complitely assembled)

AD9951 spettrogram with 50 MHz Spam F. out = 42.8 MHz

The same spettrogram for the OLD AD9851 DDS (old tecnology)

I0CG Prototype assembled into a little box (90 x 35 mm).

ED2 Prototype

I0CG DDS controller based to PIC18F252

DDS assembled for use as Collins digital VFO

AD9951 Features:

This DDS is capabe of generating a frequency-agile analog output sinusoidal waveform at up 200 MHz

Dowload the PDF description of I0CG / I0GLU PCB board implemetation (see schematics and PCB layout) AD9951.PDF

Dowload the Operation manual of my software implemetation to use DDS as Digital VFO for homebrew Transceiver dds-x.PDF

I have tested this DDS as HF VFO (1-30 MHz) that is, for the first time in the DDS VFO story,substantially birds free!

I have tested this DDS on DRAKE R4B receiver and on Elecraaft K1 transceiver; now I am working to test it on a Collins line

Also the computer control is possible with this VFO; I use HB9DRV Ham Radio Deluxe 1.3 with K2 protocol set-up


If intersted to this project please write to

DDS description on the Italian magazine "RadioKit elettronica" september 2004

I am using this DDS in my project DDS-4 VFO; DDS Digital VFO

see alsoDDS-4 Digital Tuning System see relevant WEB pages.